Final Report Summary - NANOCLEAN (Optimisation and upscaling ... by combining tailored nanostructured machined injection tools and functional thermoplastic nanocompounds)
Executive summary:
The NANOCLEAN project ('Optimization and upscaling of self-cleaning surfaces for automotive sector by combining tailored nanostructured machined injection tools and functional thermoplastic nanocompounds') was launched the 1st of October of 2009 and finished 30th September of 2012. This project was completely aligned with the approach of the call, demonstrating the feasibility of previously lab-scale Nanotechnology into an industrial Application.
The main objective of the NANOCLEAN project that is the mass-production of permanent self-cleaning 3D complex plastic components for automotive industry was fully and successfully achieved:
- MASS-PRODUCE: at least 20.000 shots has been tested
- PERMANENT: intrinsic characteristic of the component, respect to painted products and coatings.
- SELF-CLEANING: improved performance against standard products. A new methodology to quantify the 'easy-to-clean' of a plastic component has been developed as no methodology for this application is available in the literature.
- 3D COMPLEX COMPONENT: Exterior Mirror Cup as prototype of 3D component due to its size and complex geometry.
- PLASTIC: New super hydrophobic styrenic material
- AUTOMOTIVE INDUSTRY: fulfilling the specifications of OEMs (mechanical and ageing tests).
- TRANSFERABLE:
- Other automotive components: interior components or any other piece of plastic of an auto is susceptible to be achieved super hydrophobic and self-cleaning properties by this new NANOCLEAN technology.
- Other industrial sectors: white appliances, medical products, microfluidic, electric/electronic appliances, aerospace, etc.) could take profit of this technology for the same or other applications.
To achieve this global objective, the following goals has been completely reached:
- To develop tailor-made micro/nanostructured surfaces onto 3D injection moulds
- To optimize highly hydrophobic materials suitable for micro/nano-textured injection 3D moulding technology
- To design and assess of injection moulding process and moulded components
- To scale-up this assessment
According the relevance of technological and exploitation results obtained in the NANOCLEAN project, a website of the project has been created for the dissemination of those results. The link to the website is the following: http://www.nanoclean-project.eu
Project Context and Objectives:
An outstanding example of a surface phenomenon based biomimetic approach is the self-cleaning effect, i.e. the ability to keep itself clean. The most famous natural example of legendary self-cleanness is the leaf of the Lotus flower. Briefly, the 'Lotuseffect', or self-cleaning feature, is based on the superhydrophobic (waterrepelling) surface of the leaves thanks to a complicated waxy micro- to nano surface structure.
In detail, the analysis of lotus leaves by different microscopy technologies have revealed that the key feature is a specific double micro/nano scale surface consisting of arranged micropillars, with diameters ranging from 5 to 10 μm, which are covered with waxy hydrophobic hierarchical nanostructures. According to reported results, this nano-scale structure is responsible and fundamental for the highly superhydrophobic behaviour through increasing the water contact angle and enhancing the rolling behaviour of the drops. In particular, in waxy nanostructured surfaces, this nano-scale hair-like structure is responsible for an additional increase of 13-15% in water contact angle when compared to a microstructured surface, which in turn provides a high increment in the contact angle in comparison to smooth waxy surface.
The 'synthetic' engineering of these superhydrophobic surfaces have attracted great interest over the last few years, from both fundamental research and practical applications, due to being beyond doubt that a successful artificial self-cleaning surface would make our daily life much easier by extending to numerous applications, such as building facades, automotive parts, medical tools and textiles amongst others.
Up to now, to control surface wettability, i.e. to 'biomimic' surfaces with very large water contact angles and very low hysteresis allowing drops to roll off very easily (at small tilt angle), the most successful approaches have been performed through a cooperative effect of low surface free energy materials and micro/nano-structures. However, practical applications have been hampered, mainly, by expensive and/or time-consuming processes, which are not totally scalable to most industrial uses, but just to particular applications and sectors. Thus, success in practice is very limited and requires practical approaches for the development of new cost-effective and up-scalable process which may be applicable to a wide variety of sectors.
The main objective of the project that is the mass-production of permanent self-cleaning 3D complex plastic components for automotive industry could be breakdown in the following specific objectives that includes the operational objectives that must be executed for their achievement.
- To develop tailor-made micro/nanostructured surfaces onto injection moulds:
- To set-up ultra-short pulsed laser ablation based micro-nano machining technology through adjusting the design, motion, optics and programming of laser devices as well as studying the self-organising phenomena of metal surfaces under controlled pulsed laser.
- To extend the texture portfolio, designing appropriate textures according to injection moulding requirements (release phenomenon, temperature, pressure, durability ).
- To design and build machinery capable of structuring small to medium injection moulds (up to length 400 width 200 depth 100mm).
- To set-up design rules for 3D surfaces that are able to up-scale technology to design and build new concepts based laser machine capable of two-scale texturing large complex moulds.
- To characterise machined micro/nanotextured surfaces topography according to different analysis methodologies (SEM, 3D-SEM, AFM, XPS, TEM, confocal microscopy ...) and to model the nano-structure occurrence for further fine tuning of the structures and find possible new regimes.
- To assess of repeatability for replication of micro/nano patterned surfaces onto moulds. To achieve of accurate and repetitive texturing process.
- To characterise key thermal/mechanical properties of nano-machined tools for suitable technical/economical up-scaling of injection moulding technology, i.e. wear resistance, hardness, stability and durability.
- To optimise highly hydrophobic materials suitable for micro/nano-textured injection moulding technology:
- To select, develop and modify styrenic materials (extended use in automotive and other potential sectors) to tailor-made enhanced hydrophobicity and suitable flowability via combining more hydrophobic monomers and/or adding additives and nanofillers enhancing hydrophobicity during compounding and/or injection moulding processes. This approach will allow cost-effective and durable improvements that will enable large-scale production of the materials safely and economically.
- To characterise surface wetting properties via static/dynamic contact angle (advancing and receding), contact angle hysteresis, sliding angle (liquid/solid adhesion), surface energy and drops on impact (high speed processes).
- To characterise key physic/chemical properties of materials (rheology, wear, hardness, thermal stability, mechanical performance, ageing ..).
- To assess effectiveness of modification procedures (screening of a range of materials) according to rheological characterisation, quantification of static and dynamic wetting properties and self-cleaning performance. To characterise of fundamental properties (effect of modification on macroscopic behaviour).
- To design and assess of injection moulding process and moulded components:
- To optimise injection moulding and parameters for each polymer grade.
- To analyse achieved replication of transferred patterns onto injected plastic surface according to plastic material, mould topography and process conditions.
- To assess of effectiveness of the obtained micro/nano-patterns in relation to hydrophobicity and self-cleaning (antisticking of dirt). To Quantitative predict roughness effects on wettability.
- To adjust of micro/nano structures on moulds according to effective replication / self-cleaning ratio.
- To characterize of macro-scale properties of textured plastic models (wear, aesthetics, thermal properties, mechanical performance, etc.).
- To scale-up this assessment:
- To develop final industrial automotive component with enhanced self-cleaning properties by combining nano-engineering of moulds and materials.
- To characterize end-use component.
- To techno-economical assess according to yields, costs, added-value, growing demands from customers and OEMs-Original Equipment Manufacturers.
- To environmental evaluate involved procedure with a Life Cycle Assessment (LCA) methodology to perform a global environmental evaluation, determining and quantifying the relevance of key involved impacts (Ecoindicator99 methodology).
- To evaluate other functions for automotive sector (aesthetics, lighting, safety, new functions, etc.) derived from controlling wetting properties of plastic components by means of one-step injection moulding process.
- To envisage of potential transfer of up-scaled technology to other sectors and applications.
- To benchmark and assess technology focused on potential transfer of up-scaled technology to other sectors and applications thanks to proposing an integrated approach based on standard production line applied in numerous sectors.
Finally, all progress on these objectives will come together in form of an automotive component that will probe capabilities of the developed multidisciplinary process and achieved self-cleaning features. The final demonstrator will be an exterior mirror rear cup manufactured with the optimised micro/nanotextured tools and modified polymers by integrated injection moulding process. Furthermore, the project will allow assessing the predicted huge potential of the developed up-scaled technology to be used in other sectors and applications, improving competitiveness of European polymer compounders, tool manufactures and injection moulding industry.
Project Results:
Progress in nanotechnology benefits achieving new functions and features for numerous new products and applications through the knowledge-based tailored properties. However, despite these special features, there are many challenges to transfer real applications into our daily life. NANOCLEAN project seeks to demonstrate the upscaling of tailor-made nanostructured based self-cleaning feature on plastic components through cross disciplinary approach. In particular, the proposed technology is based on stable and durable so-called lotus-effect from both chemical and physical methods such as nano/micromachining - templation technologies and nanomodified materials.
The NANOCLEAN objectives are achievable through combination of cross-science and technologies on nano/functional polymers, micro-nanomachining, injection moulding, characterisation, and quality and viability control; and can be summarized in the following bullet points:
- Tailor-made micro/nanostructured surfaces onto injection moulds.
- Optimisation of highly hydrophobic materials suitable for micro/nano-textured injection moulding technology.
- Design and assessment of injection moulding process and moulded components.
- Scaling-up assessment.
Relevant research activities have been carried out within all the projects technical Work packages fulfilling the objectives of the project: WP2 (Micro/nanostructured injection tools), WP3 (Plastic materials with tailor-made enhanced hydrophobicity), WP4 (Set-up of injection-moulding) and WP5 (Up-scaling of technology).
WP2 Micro/Nano structured injection tools [Participants MAI, LIG, UT, DEM]
On the basis of previously demonstrated lab-scale processing (combined micro and nanostructuring) steel surface by femtosecond pulses for 2D small surfaces, involved partners have been worked in re-designing and up-scaling the laser machinery (workstation) for machining larger and most importantly 3D curved surfaces (two-scale micro/nano-textured metal moulds).
The objective of WP 2 has been successfully achieved by the research and development of 3D techniques for micro/nanotexturing and of the processing to up-scale based on three main parts of the workstation: (1) optimal motion hardware, (2) software and (3) laser parameters
Task 2.1 - Ultra-fast laser based micro/nano texturing workstation [Participants: LIG, DEM]
The development of the work station for ultra-fast laser based micro/nano texturing was achieved for flat moulds in Month 8 (May 2010), as planned and described in Deliverable D2.1. In this task, the three subsystems have been addressed.
(1) Motion hardware. The proposed technology has been based on two kinds of motions, macro 3D motion between laser processing head and mould in order to guide the laser spot to the desired position on the mould; and fast micro motion of the focused laser spot over the mould for the texturing process. In particular, based on a 5 axis manipulator used for manipulating the laser processing head in 5 axes in respect to the mould. The 5DOF consists of a split axis system with the linear x axis and rz rotational axis manipulating the product. These two axes were fixed on a granite baseplate. The y and z axis were attached to a granite bridge. The last (ry) rotational axis of the system was mounted to the z stage and rotated the scanner head around the optical axis of laser entering the scanner, to manipulate laser beam in 3 dimensions in a faster way considering the ne necessary accuracy of the laser focal spot on the mould.
(2) Software. Dedicated software has been developed and used to map the desired structure on a given mould geometry (CAD) and generate the setpoints for the workstation axes.
LIG's main priority during the first months was to develop the new software for scanner control mentioned above, as well as to get process research up and running. They looked into available 3D CAD/CAM software and its applicability to laser texturing. There was - as was expected - no existing CAM software capable of doing this kind of job, and so, their focus shifted quickly to finding a CAM solution that allowed them to extend its functionality with custom software to provide the CAM functionality needed. After comparison of several of the most popular 3D CAM solutions they decided to use SolidWorks, mainly for reasons of extensibility and affordability.
(3) Laser A new laser, Coherent Talisker, was obtained and modified for its use in the machine. This laser provides a 20x higher power and a wider choice of wavelengths (1064, 532, 355 nm) than the laser previously used by LIG. The new laser was integrated with the motion system in Month 7 in a flexible way; active and passive optical components can be easily placed and exchanged. This flexible layout will enable easy introduction of new components in the up scaling phase (WP5). Separate light paths for the three different wavelengths, as well as a fourth light path that allows to alternate optical set-ups and tests, were all permanently built on the system. By the use of flipmounts, mirrors guiding the beams into specific paths can be moved in and out of the light path, enabling a fast switch between wavelengths. Subsequently, the machine, called OP67, was further developed in all relevant aspects. LIG purchased a new laser that enables more robust production of the textures that will be used to upscale the laser processing speed. This new laser was integrated into the workstation, the control software was further developed towards 3D functionality and the motion hardware was further developed, as described in Deliverable D2.4 achieved in Month 14 (November 2010), entailing a successful completion of Task 2.1. Through the mentioned workstation, the 1st generation inserts for multi-nanotextured flat moulds were also manufactured and assembled by the end of Month 10 (July 2010), as stated in Task 2.2.
Task 2.2 - Multi-nanotextured flat moulds (1st generation moulds) [Participants: MAI, LIG, DEM]
In parallel with the mapping nanostructures on 3D structures, a first approach through preliminary flat surface mould has been carried out towards further more complex textured injection moulding tools. To that end, the developed motion hardware system (5 DOF manipulator), a dedicated control software to generate the set points for the workstation axes, and the laser processing equipment (Coherent Talisker laser) were successfully integrated in LIGs new facilities. The laser processing techniques for 1st generation moulds were also developed and the processing of materials by this workstation was demonstrated.
- Design and manufacture of injection mould for producing industrially used conceptual master part.
This is an essential stage for suitable efficient up-scaling and demonstration of the proposed innovative nano-texturing technology and permanent super-hydrophobicity. The proposed moulded sample was a master plaque of 200 x 160 x 2,5 mm dimensions with 4-6 micro/nano-roughness onto surface for further qualitative and quantitative characterisation. MAI was in charge of the overall design and manufacture of the master mould:
- Material: Closer to a realistic/industrial approach, the master plaque mould was made of standard materials (steel hardness). The mould material MIRRAX ESR is preferred due to better laser processing results on this material. NIMAX offers advantages for the mould manufacturing and is preferred by MAI. As both materials are still relevant for the remainder of the project, the durability test was decided to be performed on both materials.
- Conceptual design of cavity, cooling channels and injection gate: The die cavity (projected surface) was designed and manufactured as an 'interchangeable' insert (easy and dynamic changes in surface roughness patterns - range of multi-scale structures).
- Ejection: The ejection and demolding stages was analysed carefully. In particular, apart from the allocation and design, controlled robots (industrially used systems) were used to avoid handling that could damage the micro-nanostructured surface.
- Surface micro/nanostructuring of designed metal inserts
The texture parameters have been varied in their structure element spacing, element size and aspect ratio. This way injection moulded test samples are available with a broad set of properties, enabling the evaluation for specific uses and characterization in combination with different polymeric materials. 6 different textures included dimple, line and crosshatch patterns. To the experience of LIG, the properties of these textures are very similar when produced in a well replicating and hydrophobic material. The dimple pattern however is the best choice from a manufacturing point of view. For this reason, two different dimple textures were chosen, arranged in triangular shapes on the mould, in order to have similar distances in the textures to the injection gate. The dimple parameters are described below:
Dimple texture parameters:
- Arranged in a square packed pattern
- Centre to centre distance: 28 μm
- Diameter of dimples at the top: 23 μm
- Depth of shallow dimples: 11 μm
- Depth of deep dimples: 22 μm
- Assembly of injection moulds
The nanostructured moulds has been assemblied for the subsequent injection trials (WP4) for assessment, which includes the analysis of durability-stability of mould (Task 2.3).
Task 2.3 - Characterisation of nanostructured steel moulds [Participants: UT, LIG, MAI]
As a parallel task to assess the whole ultra-fast laser based texturing procedure, UT was the responsible for characterising the surface properties of every manufactured nanostructured moulds (Task 2.2 & 2.5).
- Characterisation of surface properties of submicro-textured moulds. This characterisation was focused on the key features of the proposed innovative approach, i.e topography, micro-hardness and wear resistance.
- Topography: Surface will be characterized on different levels by complementary technologies. SEM, stereo SEM, confocal microscopy and AFM was used for qualitative and quantitative evaluation of micro and nano structures.
- Hardness: To optimize the durability of textured mould surfaces the parameters that lead to an optimal hardness have to be investigated (nanoindenter technology).
- Wear: The surfaces should be designed for a maximum of wear resistance. The same surface used in the previous hardness experiments, was subjected to well-defined wear testing.
Altogether, a complete picture of material changes depending on used laser parameters and steel will be provided towards optimal up-scaling. Furthermore, these parameters were fundamental feedback data for optimisation of nanotexturing technique and mould design (Task 2.1 & 2.2) for evaluation of effectiveness of laser process, reproducibility and suitable material selection, as well as for further modelling of procedure, helpful to optimal up-scale and search for new regimes.
As a parallel task to assess the whole ultra-fast laser based texturing procedure, UT characterized through topographical, chemical and hardness analysis the surface properties of every manufactured nanostructured moulds (Task 2.2 & 2.5).
Altogether, a complete picture of material changes depending on used laser parameters and steel has been provided towards optimal up-scaling. As a result of the application of the state of the art laser technology: by ultra-short laser pulses, it has been found that the topography of the mould surface has been altered in a precise way, being in agreement with the later observed surface functionalization, but no significant change of material properties has been observed, being in agreement with the conducted industrial scale tribological analyses of the durability test of 20000 shots.
- Evaluation of durability-stability of nanostructured metal dies
The characterisation of all these parameters, together with functional performance (WP4), performed again, after injection moulding trials, to evaluate the real durability-stability of nanostructured metal moulds in process in order to evaluate the amortisation and the necessity ofcleaning or repairing operations.
An industrial durability test (20,000 shots x 2 cavity inserts) has been run at MAIs facilites to evaluate the performance of micronanotextured fields under real process conditions, with 1st generation moulds. The sample parts' surface's contact angle was measured in order to evaluate and control the surface quality of parts, obtaining average values in the range of 130-140.
Task 2.4 - Investigation of self-structuring phenomenon-modelling [Participants: UT, LIG]
In this activity, thanks to the constant monitor of obtained nanostructured topographies on metal dies (Task 2.3) modelling and a better understanding of the nanostructure occurrence was performed to tune the process, find possible new regimes and increase texture portfolio.
A thorough study of the existing theories in the field of laser-induced periodic surface structures (LIPSS) was performed from month 4 until month 20 (May 2011). A practicable and efficient empirical approach has been developed by the UT to quantify the energy input for laser machining surfaces. This approach is able to analyse and model knowledge-based of processing methods and to study phenomena like self-organising ripple patterns a chaotic micro-structuring.
As a result, an irradiation model has been developed analysing the energy input and predicting based on a simulation of the machining process quantitative values for the machining parameters, such as average laser power, scanning velocity, number of machining repetitions and machining time. The model identifies error sources influencing the machining result and gives opportunities to optimize the machining accuracy and time.
Task 2.5 - Manufacture of small to medium 3D curved micro/nanostructured moulds (2ndgeneration moulds) [Participants: MAI, LIG, DEM]
Once designed and optimised laser machinery for nanostructuring of 3D curved (Task 2.1) a new conceptual design based mould for evaluating moulded curved samples and related side effects to consider during up-scaled processing (draft as a function of roughness topography, laser effectiveness on local curved areas, variation in gloss and other aesthetic issues due to abrupt changes in angle, effect of ejection on textured 3D surfaces ..) was designed and manufactured.
- Design and manufacture of 3D complex injection mould for curved conceptual master component
Assuming the developments and achievements from Task 2.2 a re-design task was performed to manufacture a conceptual curved master plaque with different angles and curvatures to evaluate the capabilities of nanostructuring, by new concept of ultra-fast pulse laser ablation machinery (Task 2.1) against complexity of metal die.
- Nanostructuring of curved small to medium injection tools and assembly of injection moulds
As in case of Task 2.2 the designed inclined/curved inserts was surface nanostructured with different optimal tailor-made two-scale textures, by means of laser workstation. In this case, the machinery will be adapted to design geometry attending to proposed angles in order to tune laser & motion parameters to further optimised negative nanostructure on mould as a function of curve and draft angles. On the other hand, MAIER will be responsible of suitable assembling of nanostructured moulds to injection trials (WP3) and assessment (Task 2.3).
In conclusion, a 3D conceptual curved plastic part has been designed to evaluate the replication quality on micronanotextured surface of injected parts. A 2nd generation mould has also been designed and built to inject the 3D curved plastic parts with micronanotextured surfaces. This new mould is based on previous results from 1st generation mould. It includes interchangeable cavity inserts in order to evaluate different draft angles, radius of curved surfaces and micronanotextured surfaces. This task has been achieved in month 18 (March 2011).
MAIN S&T RESULTS OF WP2
- The femtosecond pulse laser based nano-structuring workstation for flat moulds was achieved by Month 8, through the successful integration of the developed motion hardware, control software and laser system/techniques.
- Significant advance has been accomplished towards the obtaining of the workstation for nano-structuring curved 3D moulds.
- The design of the NANOCLEAN flat master parts to test the developed workstation was established, regarding dimensions, material and machining process.
- The injection mould to produce the designed flat master parts was manufactured.
- The moulds assembly process in the different available injection machines was determined.
- A 3D conceptual curved plastic part has been designed to evaluate replica quality on micronanotextured surface of injected parts.
- A 2nd generation mould has been designed and built to inject 3D curved plastic parts with micronanotextured surfaces. This new mould is based on previous results from 1st generation mould. It includes interchangeable cavity inserts in order to evaluate different draft angles, radius of curved surfaces and micronanotextured surfaces.
- The 1st and 2nd generation micro/nanotextured mould was characterised through topographical, chemical and hardness analysis.
- A detailed overview of the existing LIPSS theories has been accomplished, resulting in a high knowledge on the field.
- A model has been developed to analyse the machining process and parameters for laser nano/micro structuring of metal injection mould tool surfaces
- A theory has been developed in order to explain the spatial emergence of LIPSS (self-structuring phenomenon) and further textures
Deliverables submitted in WP2:
D2.1 - Femtosecond pulse laser based nano-structuring workstation for flats moulds -M8
D2.2 - 1st generation micro/nanotextured moulds & characterization- M12
D2.3 - Self-structuring and modelling analysis of laser technology onto metal moulds - M20
D2.4 - Femtosecond pulse laser based nano-structuring workstation for curved moulds -M14
D2.5 - 2nd generation micro/nanotextured moulds and characterization- M18
WP3 Tailor-Made enhanced hydrophobic polymers [Participants: MAI, GAI, BASF]
The objectives achieved with this WP were the production, by physical-chemical-nano bottom-up approaches, an assortment of styrenic polymers with tailor-made surface wetting-properties (enhanced hydrophobicity - surface free energy) who fulfill requirements for successful use in injection moulding attending to flowability, cost-effectiveness, product quality and flexibility (easy processing, easy colouring, gloss, quality surface finish ..) and the characterization of the main properties of developed novel specialty premium plastics, with special effort on rheological and surface properties, to assess effectiveness of develop/modification procedures (screening of a range of materials).
Task 3.1 - Specialty styrenics with tailor-made surface wetting regimes [Participants: BASF, GAI, MAI]
BASF developed a new series of styrenic derived thermoplastic compounds that combine good properties and novel wetting behaviour on target self-cleanness feature. Specialty styrenic copolymers (for example - ASA [acrylate styrene acrylonitrile]) are used as injection moulded parts in automotive applications due to their excellent weathering and chemical resistance. Then, within this WP3, the intrinsic hydrophobicity of these styrenic materials (firstly focus on ASA type, although other styrene copolymers were tested like ABS and SAN) were checked.
The following strategies were used:
- Modification of polymer structure
- Addition of additives or nano-fillers
- Combination of additives and modified polymers
The hydrophobicity of ASA styrenics resin will be increased by incorporating different hydrophobic monomers in the synthesis of the polymeric material. ASA copolymer consists of two different polymeric phases: the polymer matrix composed of styrene acrylonitrile (SAN) and the butyl-acrylate rubber particles. Therefore, both phases could be altered to enhance the hydrophobicity. A series of mixtures of different additives and altered polymer were tested by means of extrusion processing.
This WP3 started in Month 6 (March 2010) with a brief literature search by BASF. This search was carried out in Chemical abstract and Derwent database. Some patents still need to be checked in more detail (especially for general description of surface structures), since no direct hit was found yet.
Moreover, before addressing the modification of polymer structure, in order to achieve a material with improved hydrophobic behaviour and high replicability, some preliminary tests were carried out by BASF. Those tests aimed at knowing exactly where the available materials stood. Three different materials were tested using an existing micro/nanotextured mould:
- Luran S (ASA, MVR 25)
- Luran (SAN, MVR 20)
- Luran (SAN, MVR 60)
For the optimal parameters used in the tests, no full replication of the structure was achieved, so the modifications of the structure and the addition of additives that would be carriedout in the subsequent months had to improve the flowability of the final material. It was found that the ASA material replicates better than the SAN material.
Task 3.2 - Characterization of fundamental and special properties of the developed assortment of new styrenic polymers [Participants: GAI, BASF, MAI]
This task involves the characterization activities to evaluate fundamental properties and further particular target effects for evaluating effectiveness of bottom-up develop/modifying procedures (Task 3.1). Both tasks have been carried out in parallel.
The following subtasks have been carried out:
- Screening polymer materials for their physical-chemical characteristics and special wetting properties by extensive testing to establish suitable selection for further experimentation.
- Establishing structure/processing/properties relationship for novel styrenics.
- Characterisation of fundamental properties of the innovative styrenic resins
According wetting properties of novel new styrenic compounds, although this subtask was planned to be carry out in WP3, finally it will be done during WP5 due to more trials were necessary to develop a methodology to evaluate the degree of 'easy-cleaning' property for styrenic compounds. GAI by means of optical high-resolution videosupported wetting surface properties measuring instrument analysed the thermodynamics between water and developed polymer surface applying different equations and methods considering contact angle and roughness: Static and dynamic contact angles, contact angle hysteresis, adhesion, surface free energies, effect of surface geometry (flat, concave & convex), etc.
MAIN S&T RESULTS OF WP3
Regarding WP3 (Plastic materials with tailor-made enhanced hydrophobicity), during the first months, a brief literature search and some preliminary tests using available materials were carried out, with the objective of having some reference points in terms of replication of the nano and micro texture, and also in terms of hydrophobic behaviour. Afterwards, during the next months, several replication quality tests were performed with different ASA materials. The replication quality was measured through the Water Contact Angle (WCA) versus the rubber content of the material and the melt and mould temperatures employed for its injection. The best results obtained presented WCAs of around 145º, which are considered as a non-sufficient replication quality.
From month 19 until month 24 (September 2011) the influence of different plasticizers on the replication of the textured mould, as well as on the superhydrophobicity of the ASA surface has been investigated, and promising results have been obtained, as WCAs of more than 150º have been measured. In addition, another commercial material (Terblend N BX) has been reviewed in detail, and investigations and modifications have been done on the replication behavior, as well as on the hydrophobic properties of the material.
In comparison to standard ASA, the material shows an excellent replication quality and lead to good peak to valley values. However it turned out that the WCA on flat as well as on textured surfaces cannot achieve the values of ASA, which presumably is the outcome of the strong hygroscopic effect of the PA component.
Further extra tests to increase the knowledge about materials behaviour have been carried out from month 24 until month 30 (March 2012) although they have not been contempled in the initial planning but their relevance has been considered critical to control the up-scaling step of the process. A variotherm injection mould has developed in order to optimize the moulding temperature. Using this mould, it is clearly seen that moulding temperature has a significant influence on the replication behavior. By this methodology it is possible to achieve, a superhydrophobic surface based on a styrene copolymer such as ASA. Best results achieved according WCA and replication behavior will be obtained with ASA material combined with a small amount of a hydrophobisation and a flow improving additive and a mould temperature higher than 110ºC (the combination was so far not tested on a variotherm mould). The material shows a significantly improved WCA and at once mechanical properties (tensile and flexure properties) within the specification for mirror cup application requested by CRF. Both tasks, 3.1 and 3.2 have been carried out in parallel until month 30 due to extra assays concerning variotherm injection moulding technology. This WP have been carried out in parallel with WP2 (until its end), forming an iterative process together with WP4 with the objective of developing an optimized process that will be scaled-up in WP5.
Deliverables submitted in WP3:
D3.1 - Report on first innovative enhanced hydrophobic styrenics (manufacture and characterisation) - M21
D3.2 - Report on up-graded styrenics (manufacture & characterisation) - M24
D3.3 - Assortment specialty styrenics with tailor-made surface wetting properties -M28
WP4 Injection moulding [Participants: MAI, GAI, UT, BASF]
Main goals that were achieved in this WP were the optimization of the injection moulding process (parameters) combining tailor-made modified polymers and nanostructured moulds for permanent (bulk) target functionalities in plastic parts (monitoring of processed polymer surface and wettability) and the development of an assessment of all-around suitability of overall innovative technology.
Task 4.1 - Injection-moulding process [Participants: GAI, MAI, UT]
The objective is to understand the effect of plastic material, nanostructure and injection moulding process parameters, in concert, on replication, to provide NANOCLEAN with the basis for further optimisation of overall process towards proposed surface functional goals.
Hence, the described testing and optimisation procedure was used with 1st and 2nd generation of nanostructured moulds (flat and curved).
Task 4.2 - Wetting properties and self-cleanness of injected components [Participants: GAI, MAI, BASF]
The wetting properties of injected components from 1st and 2nd generation of multi-nanotextured moulds (flat and curved, respectively), was evaluated to final assessment of all around effectiveness and setting up of overall process factors for further up-scaling and
Task 4.3 - Characterization of fundamental properties [Participants: GAI, MAI, BASF]
The wetting properties of injected components from 1st and 2nd generation of multi-nanotextured moulds (flat and curved, respectively), will be evaluated to final assessment of all around effectiveness and setting up of overall process factors for further up-scaling and demonstration.
MAIN S&T RESULTS FOR WP4
Injection moulding process optimization was performed considering not only replication rate but also the quality of injected specimens by varying different injection moulding parameters. Different selected injection moulding conditions have been tested to mould enough quality pre-series and derived optimised injection moulding conditions were transferred to durability tests. Some of the wetting properties, as well as other fundamental surface properties, have been evaluated for both pre-series to assess surface functionality and analyse feasibility as control quality tool for copy rate.
All the tasks from WP4 were completed for month 30 (March 2012), including the deliverable D4.2 (January 2012). 2nd. Generation mould with new selected texture was tested for the different ASA materials with the plastiziers using the standard moulding conditions. Even more, variotherm injection samples were evaluated according the static WCA by sessile drop method (parallel and perpendicular).It can be deduced from the results of the initial samples that a higher mould temperature enhances hydrophobicity.
ASA materials were tested varying injection moulding conditions. The highest water contact angles can be achieved by using high melt and mould temperature. Melt temperature should be kept at 280°C and mold temperature at 90°C. A higher mold temperature of 100°C leads to increased WCA but gives problems during ejection of the specimen. For a better WCA, an injection moulding machine which can utilize variable mould temperature during each injection might by be helpful. This would allow injection at even higher mold temperature, cooling the test specimen actively below 90°C before ejecting it.
A qualitative and quantitative characterization of topography of injection moulded plastic parts was performed and compared to injection mould inserts to evaluate replication rates and any indicative wear of textures after thousand injection moulding shots. In general, the aspect ratio of blunt textures provides advantages for different processes, such as injection moulding (filling), characterization (measurement accuracy) and laser machining (stability of form and height) compared to the sharp textures, with the subsequent improved surface functionalities (hydrophobicity and aesthetics). Furthermore, those surface properties showed a clear dependence on replication rate.
The replication quality was tested at LIG and BASF using different techniques, which agree reasonably well. Replication quality for the tested samples is not sufficient. Improving the melt flow by reducing the rubber content does not lead to a significant improvement, therefore melt flow and replication quality need to be improved by other means (addition of low molecular weight additives and/or changes in the polymer matrix).
As expected, these final performed activities related to setting up injection moulding process and evaluating surface features allowed to detect potential problems for up-scaling from described differences between lab-scale proof of concept (demonstrated superhydrophobic effect) and industrial up-scale approach, being possible to take decisions and define actions in up-scaling (WP5) towards success superhydrophobic industrial scaled plastic components.
A detailed description of results and defined actions performed in up-scaling stage (WP5) are found in the corresponding six-months reports and deliverables (deliverables 4.1- Report on injection moulding trials (1st & 2nd generation of nanostructured moulds / tailor made materials) and 4.2- Output of optimal roughness, material and process conditions for further up-scaling with large and complex parts).
Deliverables submitted in WP4:
D4.1 - Report on injection moulding trials (1st & 2nd generation of nanostructured moulds /tailor-made materials) - M20
D4.2 - Output of optimal roughness, material and process conditions for further up-scaling with large and complex parts - M28
WP5 Up-scaling technology [MAI, LIG, CRF, GAI, UT, BASF, DEM]
The main goal achieved during in this WP is the up-scaling of optimized process by integrating involved technologies, build on accumulated knowledge management and different related scenarios.
Task 5.1- Automotive specifications driven up-scaling [Participants: CRF, MAI]
CRF and MAI worked during the first twelve months on the definition of the automotive specifications driven up-scaling, as planned in Task 5.1 (Deliverable D5.1 M12). After evaluating several possibilities, the external rear view mirror cup was chosen as the part to be developed using the new hydrophobic material within the NANOCLEAN Project. Furthermore, a list of general automotive requirements for an exterior trim plastic part was elaborated and described in Deliverable D5.1 achieved in Month 12 (September 2010). A preliminary version of the suggested Self-Cleaning Test, new to the automotive industry, was also presented, even if it will still need further discussion and research in the meantime. From month 18 until month 24, the most significant testing procedures have been established, regarding chemical resistance, mechanical resistance and ageing, and preliminary tests have started to be run.
The mentioned tests are:
- Accelerating aging by atmospheric light.
- Resistance to chemical attack.
- Friction test procedure.
- Adhesion test procedure.
- Scratching.
Besides, a preliminary version of the Self Cleaning Effect Test Procedure was elaborated, as described in the mentioned document, which will have to be was further discussed among all partners.
All the mentioned tests were defined to evaluate the surface quality on injected plastic parts. According to the planning for NANOCLEAN project, preliminary sample parts with 3D micronanotextured curved surfaces will be injected by the end of M18. The first results from specified tests will allow allowed a further discussion to optimize technical details of the test procedure proposed.
Task 5.2 - Build a femtosecond pulse laser based machine capable of micro/nano-texturing complex large moulds [Participants: LIG, DEM]
Involved partners, on different machine set-up, designed and built a new up-scaled generation of ultrafast laser based texturing machine able to nanostructure large complex moulds with industrial-scale dimensions. Then, all the parameters and aspects developed in the WP2 was reconsidered towards refining and further upscaling the technology for maximum performance. A machine capable of texturing a broad range of moulds was the result.
At the same time, in Task 5.2 that has been finished in the last semester, DEM and LIG chose a new scanner concept, which has being designed in detail, manufactured and calibrated. LIG further developed the OP67 machine capabilities in terms of alignment and calibration capabilities needed for machining the demonstrator mould. The texturing software routine was refined, which will be used to generate the texture patterns accurately mapped on a curved mould surface. Furthermore LIG implemented a new 3D functionality within the running software, and new test moulds have been machined to test the laser process.
As in WP2, the activity was focused in three main topics: motion, software and laser process.
New 3D motion concept:
- Combining macro and micro scale motion.
- Design of new laser beam delivery system, capable of machining cavities.
- Integration of micro and macro motion.
- Redesign / adjustment of sensor system and software.
The fully automated texturing job of the mirror cup mould was performed successfully. The Lightmotif machine took 50 hours in total to texture the surface area of about 25.000 mm2. Note that Lightmotif chose safe settings and did not optimize for machining time. Below some snapshots made during the mould texturing are presented and a picture of the Nanostructered surface.
Task 5.3 - Manufacture of large-scale micro/nanostructured injection mould (real automotive component)[Participants: MAI, LIG, DEM, UT]
Task 5.3 started in Month 19 (April 2011) and has been focused on the design of an injection mould for a real automotive component. First, the specific component was selected; then, a CAE injection process simulation was run for it; and as a result, the design of the prototype mirror cup and its corresponding mould was performed in MAI's facilities, together with the definition of the mould's build and set-up procedure definition. This task has been finished during this last six months period (M25-M30) with a successful fully automated texturing job of the mirror cup mould developed by LIG. More detailed information is available in Deliverable 5.3.
Task 5.4 - Injection moulding of up-scaled automotive plastic component [Participants: MAI, BASF, GAI]
Task 5.4 has been initiated in month 25 (October 2011) within a comparison of heating technologies in order to achieve the enough energy to improve the injection process at industrial scale. Infrared and water/oil fluid heating technologies were selected to be checked at MAI´s injection plant. Main relevant were conclusions the need of an optimized design of a cooling system that allows to connect the mould to a Heat/Cool (Variotherm) system, depending on the combination of plastic material and process conditions to set up during the injection of the parts. Furthermore, durability tests run on 1st generation mould show that nanotextured surfaces of the cavity are able to resist greater than 20.000 shots of injection at industrial scale without significant level of damage.
The injection trials on the Nanoclean Mirror Cup mould were run at melt temperatures from 250ºC to 2800C. Actual mould temperatures were set up to 110ºC as a maximum technical limit for the available prototype mould. At higher values the mould starts to grip, due to the thermal expansion of all the metallic elements. The table (see Deliverable D5.5) shows the codification of experimental number, plastic material, melt and mould temperaures of the injection trials on the Nanoclean Mirror Cup.
Task 5.5 - Characterisation of nanostructured large parts and control of part quality [Participants: GAI, MAI, UT, BASF, CRF]
According Task 5.5 started in month 28 (January 2012), selected polymers have been characterised according their mechanical (tensile and flexure) chemical, WCA and 'cleanability' properties in CRF's laboratories. Results obtained confirm that ASA material combined with a hydrophobisation and a flow improving additive present excellent properties to be used for Nanoclean mirror cup. Considering self-cleaning features, an overall testing procedure to evaluate quantitatively the aesthetic and self-cleaning properties of master flat plaques was set-up, being possible to identify and classify self-cleaning / easy-to-clean materials according to tendency to soiling. It was demonstrated the up-scaling capabilities of proposed injection moulding technology towards self-cleaning plastic components totally dependent on texture configuration and replication rate, as well as on chemical nature of polymer. A detailed report could be found in Deliverable 5.5. Moreover, it has been included in this deliverable a risk assessment performed by the UT based on a modeling study for the mirror-cup mould.
The following characterization tests of flat and structured surface of test samples were performed:
- Weathering
- Mechanical properties (impact tests)
- Resistance to abrasion and car wash
- Cleanability
Further characterization test on mirror cap was performed, in particular:
- WCA and Cold crash test
- WCA (Water Contact Angle) Characterization
The WCA characterization performed on samples realized by MAI showed that the additive increases the WCA, achieving the expected value of 150°. In particular 30% WCA increasing was obtained from mirror polished surface to pattern surface of Luran std. Further 25% WCA increasing was obtained by patterned surface from Luran std to v4. 67% of WCA increasing was obtained from mirror polished surface of luran std to pattern surface of Luran v4.
In the previous 6 months a first 'Cleanability' testing for car interior components were performed. Hand cream and coffee were used as dirty agents. The cleanability of patterned ASA and flat ASA (back) was evaluated according to the modification of WCA before and after clean ability. WCA decreased when hand cream was used. A possible reason for this effect could be that hand cream contained TiO2, that could remain inside the porous.
During the final period the purpose was to define a procedure able to define the methods of testing the materials for cleanability keeping in mind the exterior application. For that two main procedures were defined according to soiling agents considered: dry and liquid dust.
In order to develop effective cleaning procedure, suitable for cleaning mold steel after laser texturing, we tested dry snow cleaning and ultrasonic cleaning with alcohol solvents (IPA, ethanol) and special cleaning agent (Tickopur R30).Promising results in laser debris removal by ultrasonic cleaning with Tickopur R30 agent were observed, though 100% effectiveness was not obtained.
LIPSS theory has been developed further in the UT, in order to explain the spatial emergence of nano-structures (LIPSS, self-structuring phenomenon) on up-scaled areas. The spatial emergence of LIPSS is based on accumulated fluence. The consideration of phenomenon related fluence domain boundaries allow to extend (identify) the applicable texture portfolio, determine machining parameter for extended area nano-structuring and analyze technical limitations.
Analytical approximations have been derived from the theory. These approximations are suitable practical application and has been applied for the first time to an engineering material, the NanoClean injection mould tool steel Mirrax from Uddeholm.
Task 5.6- Environmental evaluation of up-scaled nanostructuring technology [Participants:All partners]
The main goal achieved in this WP is the Life Cycle Assessment (LCA) methodology provides the option for carrying out a global evaluation considering all impacts, from the extraction of raw materials/resources for producing energy and materials necessary for the overall process, to the effluents generated in the process.
Respecting Task 5.6 an important progress has been achieve during the last months, to assess the environmental impacts derived from the manufacture of Nanoclean mirro cup. Final LCA finished in month 34 (July 2012) by GAI. As final conclusion, it can be stated that the NANOCLEAN mirror cup would show a better environmental performance than a part with the same self-cleaning functionality; in this case an ABS painted and coated part with a super hydrophobic coating. Main difference is due to the presence of fluorine compounds in the formulation of the super hydrophobic coating and the recyclable capability of NANOCLEAN mirror cup.
The following figure show shows the results of the comparison of the environmental performance of both pieces. Note that since in the first part of the assessment it was confirmed that there were no significant differences between the two scenarios proposed for the Nanoclean mirror cup, in this first figure the comparison between an ABS mirror cup and just one of the scenarios proposed for the Nanoclean mirror cup (worst case) is represented.
High contribution of ozone depletion parameter is due the fluoride composition of paints/coatings.
Deliverables submitted in WP5
D5.1 - Preliminary definition of target specifications - M12.
D5.2 - Results of synergic market surveillance and possibilities of new concept. Analysis and definition of requirements - M24.
D5.3 - Laser workstation for texturing large & complex moulds - M26.
D5.4 - Large-scale micro/nanostructured injection mould and automotive component - M30.
D5.5 - Control of part quality & Technical, economical and environmental assessment - M36
Potential Impact:
First, it is important to identify the position of each partner in the value-chain in order to explain the main impacts of the project. Next Figure shows that all partner of NANOCLEAN project fit perfectly in the value chain of the production of 'self cleaning' 3D components in the chain value.
The NANOCLEAN coordination team really believes that the project has been really successful according to exploitable results that have been achieved. Furthermore, it worthy be remark that some of the results are currently exploiting.
CRF (END USER)
Main impact is focused in the development of new value automotive components with wettability and self-cleaning properties highly competitive with other products of the market (glass/plastic spray coating, coatings by painting Metals and Composites by plasma plastics).
This new technology developed during the project for the production of a prototype (cup-mirror) with a 3D complex geometry can be easy extrapolated to other exterior and interior components of the car. Other parts could be also nano-structured in the future according the market demand. In this case, the self-cleaning property developed in this project it is not in relation with an improvement of the visibility or light transmission of the car mirror or glasses to enhance the user's safety (currently in the market it could be applied some coatings on the glass to get this property). In NANOCLEAN project, the self-cleaning property has been developed for aesthetic purposes. For instance, German market appreciate interior plastic elements of the car in white or lighter colours that easily can get dirty with dust, drinks or even with the impregnated grease of the hands. There is a kind of painted coatings with the same application, but are expensive, less durable and less environmental friendly.
Furthermore this NANOCLEAN technology can be applied not only for car components, but also for industrial and agricultural vehicles, that are exposed daily to ground, water, dirt, etc.
CRF is ready to exploit these results toward FGA and FIAT INDUSTRIAL
UT (DESIGN AND ENGINEERING)
(UT) tried with this research solvent the problem on the application of LIPSS, in the field of surface functionalization, covering the currently gap, that means:
1. Contributing with an available texture portfolio.
2. Knowledge-based processing for improved reproducible.
3. Extended large scale features.
4. Determination, and optimization of quantitative values for irradiation (machining) parameters.
Furthermore, it must be highlighted that UT has carried out a risk assessment based on a modelling study for the mirror-cup mould, due to this kind of assessment is highly demand for industries (including in the 2nd Progress Report)
LIG (ENABLING TECHNOLOGIES)
1. NANOCLEAN project resulted in a unique technology with new capabilities: 3D micro- and nanotexturing. DEM contribution to the development of the workstation.
2. Enabler for new applications in a variety of markets
3. Technology can be integrated into existing manufacturing chains
4. Improve existing products by new functionalities
5. Improve the competitiveness of manufacturing companies in Europe: SME supplier companies and end-user companies.
LIG has achieved the sale of one workstation for micromachining that can be developed supported by NANOCLEAN project.
MAI (DESIGN AND ENGINEERING)
Following exploitable results have been achieved:
1. As exploitable results for NANOCLEAN project can be considered the technical specifications related to the design, build and set-up of the mould and the auxiliary elements needed to obtain thermoplastic injected parts with micro-nanostructured surfaces.
2. MAI will offer to their customers the design and manufacture of moulds and plastic parts with Nanoclean effect, through: Showrooms, technical presentations and commercial quotations.
3. Currently risks identified by MAI could be the scratch resistance for exterior applications (automotive) and the coloured parts.
4. Possible applications are not only limited to automotive sector (front grilles, pillars, fuel caps, interior decorative parts, etc), but also could be applied to white appliances (New markets)
GAI (SUBSYSTEMS TIER 2)
1. Evaluation of self-cleaning / easy-to-clean properties of plastic components represents a promising extension of testing services for wide range of sectors and applications.
2. The suggested testing protocol is considered a good opportunity to customers in consultancy services. Although versatility; the test protocol should be improved and adapted to customers' necessities and potential regulations/normative.
3. In the future it could be considered to contact standardization bodies in order to contribute to the regulation of self-cleaning properties due there is no normative to characterize this property.
BASF (ENABLING TECHNOLOGIES)
In the case of BASF, they get direct exploitation products due to NANOCLEAN project:
1. Material supplier: Direct exploitation. Sell 'new grad' polymer to customers
2. Added value to an 'old' product and Knowhow advantage over competitor
3. Looking for further/other applications based on the 'new material'
4. Transfer gained knowhow to other styrenics
5. Offer customer a solution of an superhydrophobic surface based on styrenics
It is important to remark that 'new material' that will be patent within the results obtained in NANOCLEAN project in the short term.
MAIN CONCLUSIONS
Main exploitable results could be summarising as follows:
- Injection moulding represents a promising technology to develop a nano/microstructured surface with high performances and potentially low costs.
- ASA LURAN S757G an additional hydrophobisation and a flow improving additive, could be a potential material to be up scaled, according its moulding, wettability and mechanical properties. This is a 'new recipe' material for BASF and the mechanics of new material is acceptable for FIAT.
- Within NANOCLEAN improvements of surface in terms of easy-to-clean performances have been demonstrated. An overall testing procedure to evaluate quantitatively the aesthetic and self-cleaning features of standard master flat plaques is set-up. The tests could allow to identify self-cleaning materials and classify (ranking) the samples according to tendency to soiling considering different quantitative parameters. In the future it could be considered to contact standardization bodies in order to contribute to the regulation of self-cleaning properties due there is no normative to characterize this property
- NANOCLEAN is a good opportunity to solve comfort and safety problem with several opportunities in passengers and industrial vehicles.
- Thanks to the value chain established within NANOCLEAN it is possible to target well-established market (having a strong cost-benefits analysis) and emerging markets (with added value).
- TRL is enough high (7-8) for CRF to be transferred to product engineer to select proper components together with NANOCLEAN suppliers.
-NANOCLEAN technology could be also used several applications: biomedical, electronics, white appliances, etc.
- NANOCLEAN technology has demonstrated not only wettability and easy-to-clean properties, but also optical effects that could be used for other applications.
Main conclusions have been exposed: Micro- nanotextures can be applied to 3D curved surfaces, various mould inserts have been machined, textures are durable, preferred mould material has been identified, Knowledge on mould design for textured surfaces has been gained, working 3D texturing technology will enable numerous new applications (valuable exploitable result): wetting, friction and lubrication from engine parts, manipulation of light for optical effects and manipulation of cell adhesion for biomedical purposes.
SOCIO-ECNOMICAL IMPACT
Furthermore, social impact achieved has been considered relevant, due to the creation of employment and the development of practices for students and a Master Thesis.
NanoClean is the basis for writing one phd thesis (UT). The Results of NanoClean and the thesis can also be used as a basis for practical assignments and lectures in master and bachelor courses.
Furthermore, 2 six-monthly contracts of practices after the Degree have been carried out in CRF.
It must be remarkable the significantly staff increment of the spin-off LIG (3 new employees). LIG has been created 3 new contract employments due to NANOCLEAN project. This project has constituted a key support for the taking-off of a spin-off (LIG).
MAI expect that with the obtained results can increase its services in the medium term and the development and fabrication of automotive components with high added value for new European customers, acting like an economic engine.
Name of the scientific representative of the project's co-ordinator : Monica Solay
Title and Organisation: Maier S. Coop.
Tel: +0034- 946-259200
Fax: 946-259219
E-mail: monsol@maier.maier.es
Project website: http://www.nanoclean-project.eu
The NANOCLEAN project ('Optimization and upscaling of self-cleaning surfaces for automotive sector by combining tailored nanostructured machined injection tools and functional thermoplastic nanocompounds') was launched the 1st of October of 2009 and finished 30th September of 2012. This project was completely aligned with the approach of the call, demonstrating the feasibility of previously lab-scale Nanotechnology into an industrial Application.
The main objective of the NANOCLEAN project that is the mass-production of permanent self-cleaning 3D complex plastic components for automotive industry was fully and successfully achieved:
- MASS-PRODUCE: at least 20.000 shots has been tested
- PERMANENT: intrinsic characteristic of the component, respect to painted products and coatings.
- SELF-CLEANING: improved performance against standard products. A new methodology to quantify the 'easy-to-clean' of a plastic component has been developed as no methodology for this application is available in the literature.
- 3D COMPLEX COMPONENT: Exterior Mirror Cup as prototype of 3D component due to its size and complex geometry.
- PLASTIC: New super hydrophobic styrenic material
- AUTOMOTIVE INDUSTRY: fulfilling the specifications of OEMs (mechanical and ageing tests).
- TRANSFERABLE:
- Other automotive components: interior components or any other piece of plastic of an auto is susceptible to be achieved super hydrophobic and self-cleaning properties by this new NANOCLEAN technology.
- Other industrial sectors: white appliances, medical products, microfluidic, electric/electronic appliances, aerospace, etc.) could take profit of this technology for the same or other applications.
To achieve this global objective, the following goals has been completely reached:
- To develop tailor-made micro/nanostructured surfaces onto 3D injection moulds
- To optimize highly hydrophobic materials suitable for micro/nano-textured injection 3D moulding technology
- To design and assess of injection moulding process and moulded components
- To scale-up this assessment
According the relevance of technological and exploitation results obtained in the NANOCLEAN project, a website of the project has been created for the dissemination of those results. The link to the website is the following: http://www.nanoclean-project.eu
Project Context and Objectives:
An outstanding example of a surface phenomenon based biomimetic approach is the self-cleaning effect, i.e. the ability to keep itself clean. The most famous natural example of legendary self-cleanness is the leaf of the Lotus flower. Briefly, the 'Lotuseffect', or self-cleaning feature, is based on the superhydrophobic (waterrepelling) surface of the leaves thanks to a complicated waxy micro- to nano surface structure.
In detail, the analysis of lotus leaves by different microscopy technologies have revealed that the key feature is a specific double micro/nano scale surface consisting of arranged micropillars, with diameters ranging from 5 to 10 μm, which are covered with waxy hydrophobic hierarchical nanostructures. According to reported results, this nano-scale structure is responsible and fundamental for the highly superhydrophobic behaviour through increasing the water contact angle and enhancing the rolling behaviour of the drops. In particular, in waxy nanostructured surfaces, this nano-scale hair-like structure is responsible for an additional increase of 13-15% in water contact angle when compared to a microstructured surface, which in turn provides a high increment in the contact angle in comparison to smooth waxy surface.
The 'synthetic' engineering of these superhydrophobic surfaces have attracted great interest over the last few years, from both fundamental research and practical applications, due to being beyond doubt that a successful artificial self-cleaning surface would make our daily life much easier by extending to numerous applications, such as building facades, automotive parts, medical tools and textiles amongst others.
Up to now, to control surface wettability, i.e. to 'biomimic' surfaces with very large water contact angles and very low hysteresis allowing drops to roll off very easily (at small tilt angle), the most successful approaches have been performed through a cooperative effect of low surface free energy materials and micro/nano-structures. However, practical applications have been hampered, mainly, by expensive and/or time-consuming processes, which are not totally scalable to most industrial uses, but just to particular applications and sectors. Thus, success in practice is very limited and requires practical approaches for the development of new cost-effective and up-scalable process which may be applicable to a wide variety of sectors.
The main objective of the project that is the mass-production of permanent self-cleaning 3D complex plastic components for automotive industry could be breakdown in the following specific objectives that includes the operational objectives that must be executed for their achievement.
- To develop tailor-made micro/nanostructured surfaces onto injection moulds:
- To set-up ultra-short pulsed laser ablation based micro-nano machining technology through adjusting the design, motion, optics and programming of laser devices as well as studying the self-organising phenomena of metal surfaces under controlled pulsed laser.
- To extend the texture portfolio, designing appropriate textures according to injection moulding requirements (release phenomenon, temperature, pressure, durability ).
- To design and build machinery capable of structuring small to medium injection moulds (up to length 400 width 200 depth 100mm).
- To set-up design rules for 3D surfaces that are able to up-scale technology to design and build new concepts based laser machine capable of two-scale texturing large complex moulds.
- To characterise machined micro/nanotextured surfaces topography according to different analysis methodologies (SEM, 3D-SEM, AFM, XPS, TEM, confocal microscopy ...) and to model the nano-structure occurrence for further fine tuning of the structures and find possible new regimes.
- To assess of repeatability for replication of micro/nano patterned surfaces onto moulds. To achieve of accurate and repetitive texturing process.
- To characterise key thermal/mechanical properties of nano-machined tools for suitable technical/economical up-scaling of injection moulding technology, i.e. wear resistance, hardness, stability and durability.
- To optimise highly hydrophobic materials suitable for micro/nano-textured injection moulding technology:
- To select, develop and modify styrenic materials (extended use in automotive and other potential sectors) to tailor-made enhanced hydrophobicity and suitable flowability via combining more hydrophobic monomers and/or adding additives and nanofillers enhancing hydrophobicity during compounding and/or injection moulding processes. This approach will allow cost-effective and durable improvements that will enable large-scale production of the materials safely and economically.
- To characterise surface wetting properties via static/dynamic contact angle (advancing and receding), contact angle hysteresis, sliding angle (liquid/solid adhesion), surface energy and drops on impact (high speed processes).
- To characterise key physic/chemical properties of materials (rheology, wear, hardness, thermal stability, mechanical performance, ageing ..).
- To assess effectiveness of modification procedures (screening of a range of materials) according to rheological characterisation, quantification of static and dynamic wetting properties and self-cleaning performance. To characterise of fundamental properties (effect of modification on macroscopic behaviour).
- To design and assess of injection moulding process and moulded components:
- To optimise injection moulding and parameters for each polymer grade.
- To analyse achieved replication of transferred patterns onto injected plastic surface according to plastic material, mould topography and process conditions.
- To assess of effectiveness of the obtained micro/nano-patterns in relation to hydrophobicity and self-cleaning (antisticking of dirt). To Quantitative predict roughness effects on wettability.
- To adjust of micro/nano structures on moulds according to effective replication / self-cleaning ratio.
- To characterize of macro-scale properties of textured plastic models (wear, aesthetics, thermal properties, mechanical performance, etc.).
- To scale-up this assessment:
- To develop final industrial automotive component with enhanced self-cleaning properties by combining nano-engineering of moulds and materials.
- To characterize end-use component.
- To techno-economical assess according to yields, costs, added-value, growing demands from customers and OEMs-Original Equipment Manufacturers.
- To environmental evaluate involved procedure with a Life Cycle Assessment (LCA) methodology to perform a global environmental evaluation, determining and quantifying the relevance of key involved impacts (Ecoindicator99 methodology).
- To evaluate other functions for automotive sector (aesthetics, lighting, safety, new functions, etc.) derived from controlling wetting properties of plastic components by means of one-step injection moulding process.
- To envisage of potential transfer of up-scaled technology to other sectors and applications.
- To benchmark and assess technology focused on potential transfer of up-scaled technology to other sectors and applications thanks to proposing an integrated approach based on standard production line applied in numerous sectors.
Finally, all progress on these objectives will come together in form of an automotive component that will probe capabilities of the developed multidisciplinary process and achieved self-cleaning features. The final demonstrator will be an exterior mirror rear cup manufactured with the optimised micro/nanotextured tools and modified polymers by integrated injection moulding process. Furthermore, the project will allow assessing the predicted huge potential of the developed up-scaled technology to be used in other sectors and applications, improving competitiveness of European polymer compounders, tool manufactures and injection moulding industry.
Project Results:
Progress in nanotechnology benefits achieving new functions and features for numerous new products and applications through the knowledge-based tailored properties. However, despite these special features, there are many challenges to transfer real applications into our daily life. NANOCLEAN project seeks to demonstrate the upscaling of tailor-made nanostructured based self-cleaning feature on plastic components through cross disciplinary approach. In particular, the proposed technology is based on stable and durable so-called lotus-effect from both chemical and physical methods such as nano/micromachining - templation technologies and nanomodified materials.
The NANOCLEAN objectives are achievable through combination of cross-science and technologies on nano/functional polymers, micro-nanomachining, injection moulding, characterisation, and quality and viability control; and can be summarized in the following bullet points:
- Tailor-made micro/nanostructured surfaces onto injection moulds.
- Optimisation of highly hydrophobic materials suitable for micro/nano-textured injection moulding technology.
- Design and assessment of injection moulding process and moulded components.
- Scaling-up assessment.
Relevant research activities have been carried out within all the projects technical Work packages fulfilling the objectives of the project: WP2 (Micro/nanostructured injection tools), WP3 (Plastic materials with tailor-made enhanced hydrophobicity), WP4 (Set-up of injection-moulding) and WP5 (Up-scaling of technology).
WP2 Micro/Nano structured injection tools [Participants MAI, LIG, UT, DEM]
On the basis of previously demonstrated lab-scale processing (combined micro and nanostructuring) steel surface by femtosecond pulses for 2D small surfaces, involved partners have been worked in re-designing and up-scaling the laser machinery (workstation) for machining larger and most importantly 3D curved surfaces (two-scale micro/nano-textured metal moulds).
The objective of WP 2 has been successfully achieved by the research and development of 3D techniques for micro/nanotexturing and of the processing to up-scale based on three main parts of the workstation: (1) optimal motion hardware, (2) software and (3) laser parameters
Task 2.1 - Ultra-fast laser based micro/nano texturing workstation [Participants: LIG, DEM]
The development of the work station for ultra-fast laser based micro/nano texturing was achieved for flat moulds in Month 8 (May 2010), as planned and described in Deliverable D2.1. In this task, the three subsystems have been addressed.
(1) Motion hardware. The proposed technology has been based on two kinds of motions, macro 3D motion between laser processing head and mould in order to guide the laser spot to the desired position on the mould; and fast micro motion of the focused laser spot over the mould for the texturing process. In particular, based on a 5 axis manipulator used for manipulating the laser processing head in 5 axes in respect to the mould. The 5DOF consists of a split axis system with the linear x axis and rz rotational axis manipulating the product. These two axes were fixed on a granite baseplate. The y and z axis were attached to a granite bridge. The last (ry) rotational axis of the system was mounted to the z stage and rotated the scanner head around the optical axis of laser entering the scanner, to manipulate laser beam in 3 dimensions in a faster way considering the ne necessary accuracy of the laser focal spot on the mould.
(2) Software. Dedicated software has been developed and used to map the desired structure on a given mould geometry (CAD) and generate the setpoints for the workstation axes.
LIG's main priority during the first months was to develop the new software for scanner control mentioned above, as well as to get process research up and running. They looked into available 3D CAD/CAM software and its applicability to laser texturing. There was - as was expected - no existing CAM software capable of doing this kind of job, and so, their focus shifted quickly to finding a CAM solution that allowed them to extend its functionality with custom software to provide the CAM functionality needed. After comparison of several of the most popular 3D CAM solutions they decided to use SolidWorks, mainly for reasons of extensibility and affordability.
(3) Laser A new laser, Coherent Talisker, was obtained and modified for its use in the machine. This laser provides a 20x higher power and a wider choice of wavelengths (1064, 532, 355 nm) than the laser previously used by LIG. The new laser was integrated with the motion system in Month 7 in a flexible way; active and passive optical components can be easily placed and exchanged. This flexible layout will enable easy introduction of new components in the up scaling phase (WP5). Separate light paths for the three different wavelengths, as well as a fourth light path that allows to alternate optical set-ups and tests, were all permanently built on the system. By the use of flipmounts, mirrors guiding the beams into specific paths can be moved in and out of the light path, enabling a fast switch between wavelengths. Subsequently, the machine, called OP67, was further developed in all relevant aspects. LIG purchased a new laser that enables more robust production of the textures that will be used to upscale the laser processing speed. This new laser was integrated into the workstation, the control software was further developed towards 3D functionality and the motion hardware was further developed, as described in Deliverable D2.4 achieved in Month 14 (November 2010), entailing a successful completion of Task 2.1. Through the mentioned workstation, the 1st generation inserts for multi-nanotextured flat moulds were also manufactured and assembled by the end of Month 10 (July 2010), as stated in Task 2.2.
Task 2.2 - Multi-nanotextured flat moulds (1st generation moulds) [Participants: MAI, LIG, DEM]
In parallel with the mapping nanostructures on 3D structures, a first approach through preliminary flat surface mould has been carried out towards further more complex textured injection moulding tools. To that end, the developed motion hardware system (5 DOF manipulator), a dedicated control software to generate the set points for the workstation axes, and the laser processing equipment (Coherent Talisker laser) were successfully integrated in LIGs new facilities. The laser processing techniques for 1st generation moulds were also developed and the processing of materials by this workstation was demonstrated.
- Design and manufacture of injection mould for producing industrially used conceptual master part.
This is an essential stage for suitable efficient up-scaling and demonstration of the proposed innovative nano-texturing technology and permanent super-hydrophobicity. The proposed moulded sample was a master plaque of 200 x 160 x 2,5 mm dimensions with 4-6 micro/nano-roughness onto surface for further qualitative and quantitative characterisation. MAI was in charge of the overall design and manufacture of the master mould:
- Material: Closer to a realistic/industrial approach, the master plaque mould was made of standard materials (steel hardness). The mould material MIRRAX ESR is preferred due to better laser processing results on this material. NIMAX offers advantages for the mould manufacturing and is preferred by MAI. As both materials are still relevant for the remainder of the project, the durability test was decided to be performed on both materials.
- Conceptual design of cavity, cooling channels and injection gate: The die cavity (projected surface) was designed and manufactured as an 'interchangeable' insert (easy and dynamic changes in surface roughness patterns - range of multi-scale structures).
- Ejection: The ejection and demolding stages was analysed carefully. In particular, apart from the allocation and design, controlled robots (industrially used systems) were used to avoid handling that could damage the micro-nanostructured surface.
- Surface micro/nanostructuring of designed metal inserts
The texture parameters have been varied in their structure element spacing, element size and aspect ratio. This way injection moulded test samples are available with a broad set of properties, enabling the evaluation for specific uses and characterization in combination with different polymeric materials. 6 different textures included dimple, line and crosshatch patterns. To the experience of LIG, the properties of these textures are very similar when produced in a well replicating and hydrophobic material. The dimple pattern however is the best choice from a manufacturing point of view. For this reason, two different dimple textures were chosen, arranged in triangular shapes on the mould, in order to have similar distances in the textures to the injection gate. The dimple parameters are described below:
Dimple texture parameters:
- Arranged in a square packed pattern
- Centre to centre distance: 28 μm
- Diameter of dimples at the top: 23 μm
- Depth of shallow dimples: 11 μm
- Depth of deep dimples: 22 μm
- Assembly of injection moulds
The nanostructured moulds has been assemblied for the subsequent injection trials (WP4) for assessment, which includes the analysis of durability-stability of mould (Task 2.3).
Task 2.3 - Characterisation of nanostructured steel moulds [Participants: UT, LIG, MAI]
As a parallel task to assess the whole ultra-fast laser based texturing procedure, UT was the responsible for characterising the surface properties of every manufactured nanostructured moulds (Task 2.2 & 2.5).
- Characterisation of surface properties of submicro-textured moulds. This characterisation was focused on the key features of the proposed innovative approach, i.e topography, micro-hardness and wear resistance.
- Topography: Surface will be characterized on different levels by complementary technologies. SEM, stereo SEM, confocal microscopy and AFM was used for qualitative and quantitative evaluation of micro and nano structures.
- Hardness: To optimize the durability of textured mould surfaces the parameters that lead to an optimal hardness have to be investigated (nanoindenter technology).
- Wear: The surfaces should be designed for a maximum of wear resistance. The same surface used in the previous hardness experiments, was subjected to well-defined wear testing.
Altogether, a complete picture of material changes depending on used laser parameters and steel will be provided towards optimal up-scaling. Furthermore, these parameters were fundamental feedback data for optimisation of nanotexturing technique and mould design (Task 2.1 & 2.2) for evaluation of effectiveness of laser process, reproducibility and suitable material selection, as well as for further modelling of procedure, helpful to optimal up-scale and search for new regimes.
As a parallel task to assess the whole ultra-fast laser based texturing procedure, UT characterized through topographical, chemical and hardness analysis the surface properties of every manufactured nanostructured moulds (Task 2.2 & 2.5).
Altogether, a complete picture of material changes depending on used laser parameters and steel has been provided towards optimal up-scaling. As a result of the application of the state of the art laser technology: by ultra-short laser pulses, it has been found that the topography of the mould surface has been altered in a precise way, being in agreement with the later observed surface functionalization, but no significant change of material properties has been observed, being in agreement with the conducted industrial scale tribological analyses of the durability test of 20000 shots.
- Evaluation of durability-stability of nanostructured metal dies
The characterisation of all these parameters, together with functional performance (WP4), performed again, after injection moulding trials, to evaluate the real durability-stability of nanostructured metal moulds in process in order to evaluate the amortisation and the necessity ofcleaning or repairing operations.
An industrial durability test (20,000 shots x 2 cavity inserts) has been run at MAIs facilites to evaluate the performance of micronanotextured fields under real process conditions, with 1st generation moulds. The sample parts' surface's contact angle was measured in order to evaluate and control the surface quality of parts, obtaining average values in the range of 130-140.
Task 2.4 - Investigation of self-structuring phenomenon-modelling [Participants: UT, LIG]
In this activity, thanks to the constant monitor of obtained nanostructured topographies on metal dies (Task 2.3) modelling and a better understanding of the nanostructure occurrence was performed to tune the process, find possible new regimes and increase texture portfolio.
A thorough study of the existing theories in the field of laser-induced periodic surface structures (LIPSS) was performed from month 4 until month 20 (May 2011). A practicable and efficient empirical approach has been developed by the UT to quantify the energy input for laser machining surfaces. This approach is able to analyse and model knowledge-based of processing methods and to study phenomena like self-organising ripple patterns a chaotic micro-structuring.
As a result, an irradiation model has been developed analysing the energy input and predicting based on a simulation of the machining process quantitative values for the machining parameters, such as average laser power, scanning velocity, number of machining repetitions and machining time. The model identifies error sources influencing the machining result and gives opportunities to optimize the machining accuracy and time.
Task 2.5 - Manufacture of small to medium 3D curved micro/nanostructured moulds (2ndgeneration moulds) [Participants: MAI, LIG, DEM]
Once designed and optimised laser machinery for nanostructuring of 3D curved (Task 2.1) a new conceptual design based mould for evaluating moulded curved samples and related side effects to consider during up-scaled processing (draft as a function of roughness topography, laser effectiveness on local curved areas, variation in gloss and other aesthetic issues due to abrupt changes in angle, effect of ejection on textured 3D surfaces ..) was designed and manufactured.
- Design and manufacture of 3D complex injection mould for curved conceptual master component
Assuming the developments and achievements from Task 2.2 a re-design task was performed to manufacture a conceptual curved master plaque with different angles and curvatures to evaluate the capabilities of nanostructuring, by new concept of ultra-fast pulse laser ablation machinery (Task 2.1) against complexity of metal die.
- Nanostructuring of curved small to medium injection tools and assembly of injection moulds
As in case of Task 2.2 the designed inclined/curved inserts was surface nanostructured with different optimal tailor-made two-scale textures, by means of laser workstation. In this case, the machinery will be adapted to design geometry attending to proposed angles in order to tune laser & motion parameters to further optimised negative nanostructure on mould as a function of curve and draft angles. On the other hand, MAIER will be responsible of suitable assembling of nanostructured moulds to injection trials (WP3) and assessment (Task 2.3).
In conclusion, a 3D conceptual curved plastic part has been designed to evaluate the replication quality on micronanotextured surface of injected parts. A 2nd generation mould has also been designed and built to inject the 3D curved plastic parts with micronanotextured surfaces. This new mould is based on previous results from 1st generation mould. It includes interchangeable cavity inserts in order to evaluate different draft angles, radius of curved surfaces and micronanotextured surfaces. This task has been achieved in month 18 (March 2011).
MAIN S&T RESULTS OF WP2
- The femtosecond pulse laser based nano-structuring workstation for flat moulds was achieved by Month 8, through the successful integration of the developed motion hardware, control software and laser system/techniques.
- Significant advance has been accomplished towards the obtaining of the workstation for nano-structuring curved 3D moulds.
- The design of the NANOCLEAN flat master parts to test the developed workstation was established, regarding dimensions, material and machining process.
- The injection mould to produce the designed flat master parts was manufactured.
- The moulds assembly process in the different available injection machines was determined.
- A 3D conceptual curved plastic part has been designed to evaluate replica quality on micronanotextured surface of injected parts.
- A 2nd generation mould has been designed and built to inject 3D curved plastic parts with micronanotextured surfaces. This new mould is based on previous results from 1st generation mould. It includes interchangeable cavity inserts in order to evaluate different draft angles, radius of curved surfaces and micronanotextured surfaces.
- The 1st and 2nd generation micro/nanotextured mould was characterised through topographical, chemical and hardness analysis.
- A detailed overview of the existing LIPSS theories has been accomplished, resulting in a high knowledge on the field.
- A model has been developed to analyse the machining process and parameters for laser nano/micro structuring of metal injection mould tool surfaces
- A theory has been developed in order to explain the spatial emergence of LIPSS (self-structuring phenomenon) and further textures
Deliverables submitted in WP2:
D2.1 - Femtosecond pulse laser based nano-structuring workstation for flats moulds -M8
D2.2 - 1st generation micro/nanotextured moulds & characterization- M12
D2.3 - Self-structuring and modelling analysis of laser technology onto metal moulds - M20
D2.4 - Femtosecond pulse laser based nano-structuring workstation for curved moulds -M14
D2.5 - 2nd generation micro/nanotextured moulds and characterization- M18
WP3 Tailor-Made enhanced hydrophobic polymers [Participants: MAI, GAI, BASF]
The objectives achieved with this WP were the production, by physical-chemical-nano bottom-up approaches, an assortment of styrenic polymers with tailor-made surface wetting-properties (enhanced hydrophobicity - surface free energy) who fulfill requirements for successful use in injection moulding attending to flowability, cost-effectiveness, product quality and flexibility (easy processing, easy colouring, gloss, quality surface finish ..) and the characterization of the main properties of developed novel specialty premium plastics, with special effort on rheological and surface properties, to assess effectiveness of develop/modification procedures (screening of a range of materials).
Task 3.1 - Specialty styrenics with tailor-made surface wetting regimes [Participants: BASF, GAI, MAI]
BASF developed a new series of styrenic derived thermoplastic compounds that combine good properties and novel wetting behaviour on target self-cleanness feature. Specialty styrenic copolymers (for example - ASA [acrylate styrene acrylonitrile]) are used as injection moulded parts in automotive applications due to their excellent weathering and chemical resistance. Then, within this WP3, the intrinsic hydrophobicity of these styrenic materials (firstly focus on ASA type, although other styrene copolymers were tested like ABS and SAN) were checked.
The following strategies were used:
- Modification of polymer structure
- Addition of additives or nano-fillers
- Combination of additives and modified polymers
The hydrophobicity of ASA styrenics resin will be increased by incorporating different hydrophobic monomers in the synthesis of the polymeric material. ASA copolymer consists of two different polymeric phases: the polymer matrix composed of styrene acrylonitrile (SAN) and the butyl-acrylate rubber particles. Therefore, both phases could be altered to enhance the hydrophobicity. A series of mixtures of different additives and altered polymer were tested by means of extrusion processing.
This WP3 started in Month 6 (March 2010) with a brief literature search by BASF. This search was carried out in Chemical abstract and Derwent database. Some patents still need to be checked in more detail (especially for general description of surface structures), since no direct hit was found yet.
Moreover, before addressing the modification of polymer structure, in order to achieve a material with improved hydrophobic behaviour and high replicability, some preliminary tests were carried out by BASF. Those tests aimed at knowing exactly where the available materials stood. Three different materials were tested using an existing micro/nanotextured mould:
- Luran S (ASA, MVR 25)
- Luran (SAN, MVR 20)
- Luran (SAN, MVR 60)
For the optimal parameters used in the tests, no full replication of the structure was achieved, so the modifications of the structure and the addition of additives that would be carriedout in the subsequent months had to improve the flowability of the final material. It was found that the ASA material replicates better than the SAN material.
Task 3.2 - Characterization of fundamental and special properties of the developed assortment of new styrenic polymers [Participants: GAI, BASF, MAI]
This task involves the characterization activities to evaluate fundamental properties and further particular target effects for evaluating effectiveness of bottom-up develop/modifying procedures (Task 3.1). Both tasks have been carried out in parallel.
The following subtasks have been carried out:
- Screening polymer materials for their physical-chemical characteristics and special wetting properties by extensive testing to establish suitable selection for further experimentation.
- Establishing structure/processing/properties relationship for novel styrenics.
- Characterisation of fundamental properties of the innovative styrenic resins
According wetting properties of novel new styrenic compounds, although this subtask was planned to be carry out in WP3, finally it will be done during WP5 due to more trials were necessary to develop a methodology to evaluate the degree of 'easy-cleaning' property for styrenic compounds. GAI by means of optical high-resolution videosupported wetting surface properties measuring instrument analysed the thermodynamics between water and developed polymer surface applying different equations and methods considering contact angle and roughness: Static and dynamic contact angles, contact angle hysteresis, adhesion, surface free energies, effect of surface geometry (flat, concave & convex), etc.
MAIN S&T RESULTS OF WP3
Regarding WP3 (Plastic materials with tailor-made enhanced hydrophobicity), during the first months, a brief literature search and some preliminary tests using available materials were carried out, with the objective of having some reference points in terms of replication of the nano and micro texture, and also in terms of hydrophobic behaviour. Afterwards, during the next months, several replication quality tests were performed with different ASA materials. The replication quality was measured through the Water Contact Angle (WCA) versus the rubber content of the material and the melt and mould temperatures employed for its injection. The best results obtained presented WCAs of around 145º, which are considered as a non-sufficient replication quality.
From month 19 until month 24 (September 2011) the influence of different plasticizers on the replication of the textured mould, as well as on the superhydrophobicity of the ASA surface has been investigated, and promising results have been obtained, as WCAs of more than 150º have been measured. In addition, another commercial material (Terblend N BX) has been reviewed in detail, and investigations and modifications have been done on the replication behavior, as well as on the hydrophobic properties of the material.
In comparison to standard ASA, the material shows an excellent replication quality and lead to good peak to valley values. However it turned out that the WCA on flat as well as on textured surfaces cannot achieve the values of ASA, which presumably is the outcome of the strong hygroscopic effect of the PA component.
Further extra tests to increase the knowledge about materials behaviour have been carried out from month 24 until month 30 (March 2012) although they have not been contempled in the initial planning but their relevance has been considered critical to control the up-scaling step of the process. A variotherm injection mould has developed in order to optimize the moulding temperature. Using this mould, it is clearly seen that moulding temperature has a significant influence on the replication behavior. By this methodology it is possible to achieve, a superhydrophobic surface based on a styrene copolymer such as ASA. Best results achieved according WCA and replication behavior will be obtained with ASA material combined with a small amount of a hydrophobisation and a flow improving additive and a mould temperature higher than 110ºC (the combination was so far not tested on a variotherm mould). The material shows a significantly improved WCA and at once mechanical properties (tensile and flexure properties) within the specification for mirror cup application requested by CRF. Both tasks, 3.1 and 3.2 have been carried out in parallel until month 30 due to extra assays concerning variotherm injection moulding technology. This WP have been carried out in parallel with WP2 (until its end), forming an iterative process together with WP4 with the objective of developing an optimized process that will be scaled-up in WP5.
Deliverables submitted in WP3:
D3.1 - Report on first innovative enhanced hydrophobic styrenics (manufacture and characterisation) - M21
D3.2 - Report on up-graded styrenics (manufacture & characterisation) - M24
D3.3 - Assortment specialty styrenics with tailor-made surface wetting properties -M28
WP4 Injection moulding [Participants: MAI, GAI, UT, BASF]
Main goals that were achieved in this WP were the optimization of the injection moulding process (parameters) combining tailor-made modified polymers and nanostructured moulds for permanent (bulk) target functionalities in plastic parts (monitoring of processed polymer surface and wettability) and the development of an assessment of all-around suitability of overall innovative technology.
Task 4.1 - Injection-moulding process [Participants: GAI, MAI, UT]
The objective is to understand the effect of plastic material, nanostructure and injection moulding process parameters, in concert, on replication, to provide NANOCLEAN with the basis for further optimisation of overall process towards proposed surface functional goals.
Hence, the described testing and optimisation procedure was used with 1st and 2nd generation of nanostructured moulds (flat and curved).
Task 4.2 - Wetting properties and self-cleanness of injected components [Participants: GAI, MAI, BASF]
The wetting properties of injected components from 1st and 2nd generation of multi-nanotextured moulds (flat and curved, respectively), was evaluated to final assessment of all around effectiveness and setting up of overall process factors for further up-scaling and
Task 4.3 - Characterization of fundamental properties [Participants: GAI, MAI, BASF]
The wetting properties of injected components from 1st and 2nd generation of multi-nanotextured moulds (flat and curved, respectively), will be evaluated to final assessment of all around effectiveness and setting up of overall process factors for further up-scaling and demonstration.
MAIN S&T RESULTS FOR WP4
Injection moulding process optimization was performed considering not only replication rate but also the quality of injected specimens by varying different injection moulding parameters. Different selected injection moulding conditions have been tested to mould enough quality pre-series and derived optimised injection moulding conditions were transferred to durability tests. Some of the wetting properties, as well as other fundamental surface properties, have been evaluated for both pre-series to assess surface functionality and analyse feasibility as control quality tool for copy rate.
All the tasks from WP4 were completed for month 30 (March 2012), including the deliverable D4.2 (January 2012). 2nd. Generation mould with new selected texture was tested for the different ASA materials with the plastiziers using the standard moulding conditions. Even more, variotherm injection samples were evaluated according the static WCA by sessile drop method (parallel and perpendicular).It can be deduced from the results of the initial samples that a higher mould temperature enhances hydrophobicity.
ASA materials were tested varying injection moulding conditions. The highest water contact angles can be achieved by using high melt and mould temperature. Melt temperature should be kept at 280°C and mold temperature at 90°C. A higher mold temperature of 100°C leads to increased WCA but gives problems during ejection of the specimen. For a better WCA, an injection moulding machine which can utilize variable mould temperature during each injection might by be helpful. This would allow injection at even higher mold temperature, cooling the test specimen actively below 90°C before ejecting it.
A qualitative and quantitative characterization of topography of injection moulded plastic parts was performed and compared to injection mould inserts to evaluate replication rates and any indicative wear of textures after thousand injection moulding shots. In general, the aspect ratio of blunt textures provides advantages for different processes, such as injection moulding (filling), characterization (measurement accuracy) and laser machining (stability of form and height) compared to the sharp textures, with the subsequent improved surface functionalities (hydrophobicity and aesthetics). Furthermore, those surface properties showed a clear dependence on replication rate.
The replication quality was tested at LIG and BASF using different techniques, which agree reasonably well. Replication quality for the tested samples is not sufficient. Improving the melt flow by reducing the rubber content does not lead to a significant improvement, therefore melt flow and replication quality need to be improved by other means (addition of low molecular weight additives and/or changes in the polymer matrix).
As expected, these final performed activities related to setting up injection moulding process and evaluating surface features allowed to detect potential problems for up-scaling from described differences between lab-scale proof of concept (demonstrated superhydrophobic effect) and industrial up-scale approach, being possible to take decisions and define actions in up-scaling (WP5) towards success superhydrophobic industrial scaled plastic components.
A detailed description of results and defined actions performed in up-scaling stage (WP5) are found in the corresponding six-months reports and deliverables (deliverables 4.1- Report on injection moulding trials (1st & 2nd generation of nanostructured moulds / tailor made materials) and 4.2- Output of optimal roughness, material and process conditions for further up-scaling with large and complex parts).
Deliverables submitted in WP4:
D4.1 - Report on injection moulding trials (1st & 2nd generation of nanostructured moulds /tailor-made materials) - M20
D4.2 - Output of optimal roughness, material and process conditions for further up-scaling with large and complex parts - M28
WP5 Up-scaling technology [MAI, LIG, CRF, GAI, UT, BASF, DEM]
The main goal achieved during in this WP is the up-scaling of optimized process by integrating involved technologies, build on accumulated knowledge management and different related scenarios.
Task 5.1- Automotive specifications driven up-scaling [Participants: CRF, MAI]
CRF and MAI worked during the first twelve months on the definition of the automotive specifications driven up-scaling, as planned in Task 5.1 (Deliverable D5.1 M12). After evaluating several possibilities, the external rear view mirror cup was chosen as the part to be developed using the new hydrophobic material within the NANOCLEAN Project. Furthermore, a list of general automotive requirements for an exterior trim plastic part was elaborated and described in Deliverable D5.1 achieved in Month 12 (September 2010). A preliminary version of the suggested Self-Cleaning Test, new to the automotive industry, was also presented, even if it will still need further discussion and research in the meantime. From month 18 until month 24, the most significant testing procedures have been established, regarding chemical resistance, mechanical resistance and ageing, and preliminary tests have started to be run.
The mentioned tests are:
- Accelerating aging by atmospheric light.
- Resistance to chemical attack.
- Friction test procedure.
- Adhesion test procedure.
- Scratching.
Besides, a preliminary version of the Self Cleaning Effect Test Procedure was elaborated, as described in the mentioned document, which will have to be was further discussed among all partners.
All the mentioned tests were defined to evaluate the surface quality on injected plastic parts. According to the planning for NANOCLEAN project, preliminary sample parts with 3D micronanotextured curved surfaces will be injected by the end of M18. The first results from specified tests will allow allowed a further discussion to optimize technical details of the test procedure proposed.
Task 5.2 - Build a femtosecond pulse laser based machine capable of micro/nano-texturing complex large moulds [Participants: LIG, DEM]
Involved partners, on different machine set-up, designed and built a new up-scaled generation of ultrafast laser based texturing machine able to nanostructure large complex moulds with industrial-scale dimensions. Then, all the parameters and aspects developed in the WP2 was reconsidered towards refining and further upscaling the technology for maximum performance. A machine capable of texturing a broad range of moulds was the result.
At the same time, in Task 5.2 that has been finished in the last semester, DEM and LIG chose a new scanner concept, which has being designed in detail, manufactured and calibrated. LIG further developed the OP67 machine capabilities in terms of alignment and calibration capabilities needed for machining the demonstrator mould. The texturing software routine was refined, which will be used to generate the texture patterns accurately mapped on a curved mould surface. Furthermore LIG implemented a new 3D functionality within the running software, and new test moulds have been machined to test the laser process.
As in WP2, the activity was focused in three main topics: motion, software and laser process.
New 3D motion concept:
- Combining macro and micro scale motion.
- Design of new laser beam delivery system, capable of machining cavities.
- Integration of micro and macro motion.
- Redesign / adjustment of sensor system and software.
The fully automated texturing job of the mirror cup mould was performed successfully. The Lightmotif machine took 50 hours in total to texture the surface area of about 25.000 mm2. Note that Lightmotif chose safe settings and did not optimize for machining time. Below some snapshots made during the mould texturing are presented and a picture of the Nanostructered surface.
Task 5.3 - Manufacture of large-scale micro/nanostructured injection mould (real automotive component)[Participants: MAI, LIG, DEM, UT]
Task 5.3 started in Month 19 (April 2011) and has been focused on the design of an injection mould for a real automotive component. First, the specific component was selected; then, a CAE injection process simulation was run for it; and as a result, the design of the prototype mirror cup and its corresponding mould was performed in MAI's facilities, together with the definition of the mould's build and set-up procedure definition. This task has been finished during this last six months period (M25-M30) with a successful fully automated texturing job of the mirror cup mould developed by LIG. More detailed information is available in Deliverable 5.3.
Task 5.4 - Injection moulding of up-scaled automotive plastic component [Participants: MAI, BASF, GAI]
Task 5.4 has been initiated in month 25 (October 2011) within a comparison of heating technologies in order to achieve the enough energy to improve the injection process at industrial scale. Infrared and water/oil fluid heating technologies were selected to be checked at MAI´s injection plant. Main relevant were conclusions the need of an optimized design of a cooling system that allows to connect the mould to a Heat/Cool (Variotherm) system, depending on the combination of plastic material and process conditions to set up during the injection of the parts. Furthermore, durability tests run on 1st generation mould show that nanotextured surfaces of the cavity are able to resist greater than 20.000 shots of injection at industrial scale without significant level of damage.
The injection trials on the Nanoclean Mirror Cup mould were run at melt temperatures from 250ºC to 2800C. Actual mould temperatures were set up to 110ºC as a maximum technical limit for the available prototype mould. At higher values the mould starts to grip, due to the thermal expansion of all the metallic elements. The table (see Deliverable D5.5) shows the codification of experimental number, plastic material, melt and mould temperaures of the injection trials on the Nanoclean Mirror Cup.
Task 5.5 - Characterisation of nanostructured large parts and control of part quality [Participants: GAI, MAI, UT, BASF, CRF]
According Task 5.5 started in month 28 (January 2012), selected polymers have been characterised according their mechanical (tensile and flexure) chemical, WCA and 'cleanability' properties in CRF's laboratories. Results obtained confirm that ASA material combined with a hydrophobisation and a flow improving additive present excellent properties to be used for Nanoclean mirror cup. Considering self-cleaning features, an overall testing procedure to evaluate quantitatively the aesthetic and self-cleaning properties of master flat plaques was set-up, being possible to identify and classify self-cleaning / easy-to-clean materials according to tendency to soiling. It was demonstrated the up-scaling capabilities of proposed injection moulding technology towards self-cleaning plastic components totally dependent on texture configuration and replication rate, as well as on chemical nature of polymer. A detailed report could be found in Deliverable 5.5. Moreover, it has been included in this deliverable a risk assessment performed by the UT based on a modeling study for the mirror-cup mould.
The following characterization tests of flat and structured surface of test samples were performed:
- Weathering
- Mechanical properties (impact tests)
- Resistance to abrasion and car wash
- Cleanability
Further characterization test on mirror cap was performed, in particular:
- WCA and Cold crash test
- WCA (Water Contact Angle) Characterization
The WCA characterization performed on samples realized by MAI showed that the additive increases the WCA, achieving the expected value of 150°. In particular 30% WCA increasing was obtained from mirror polished surface to pattern surface of Luran std. Further 25% WCA increasing was obtained by patterned surface from Luran std to v4. 67% of WCA increasing was obtained from mirror polished surface of luran std to pattern surface of Luran v4.
In the previous 6 months a first 'Cleanability' testing for car interior components were performed. Hand cream and coffee were used as dirty agents. The cleanability of patterned ASA and flat ASA (back) was evaluated according to the modification of WCA before and after clean ability. WCA decreased when hand cream was used. A possible reason for this effect could be that hand cream contained TiO2, that could remain inside the porous.
During the final period the purpose was to define a procedure able to define the methods of testing the materials for cleanability keeping in mind the exterior application. For that two main procedures were defined according to soiling agents considered: dry and liquid dust.
In order to develop effective cleaning procedure, suitable for cleaning mold steel after laser texturing, we tested dry snow cleaning and ultrasonic cleaning with alcohol solvents (IPA, ethanol) and special cleaning agent (Tickopur R30).Promising results in laser debris removal by ultrasonic cleaning with Tickopur R30 agent were observed, though 100% effectiveness was not obtained.
LIPSS theory has been developed further in the UT, in order to explain the spatial emergence of nano-structures (LIPSS, self-structuring phenomenon) on up-scaled areas. The spatial emergence of LIPSS is based on accumulated fluence. The consideration of phenomenon related fluence domain boundaries allow to extend (identify) the applicable texture portfolio, determine machining parameter for extended area nano-structuring and analyze technical limitations.
Analytical approximations have been derived from the theory. These approximations are suitable practical application and has been applied for the first time to an engineering material, the NanoClean injection mould tool steel Mirrax from Uddeholm.
Task 5.6- Environmental evaluation of up-scaled nanostructuring technology [Participants:All partners]
The main goal achieved in this WP is the Life Cycle Assessment (LCA) methodology provides the option for carrying out a global evaluation considering all impacts, from the extraction of raw materials/resources for producing energy and materials necessary for the overall process, to the effluents generated in the process.
Respecting Task 5.6 an important progress has been achieve during the last months, to assess the environmental impacts derived from the manufacture of Nanoclean mirro cup. Final LCA finished in month 34 (July 2012) by GAI. As final conclusion, it can be stated that the NANOCLEAN mirror cup would show a better environmental performance than a part with the same self-cleaning functionality; in this case an ABS painted and coated part with a super hydrophobic coating. Main difference is due to the presence of fluorine compounds in the formulation of the super hydrophobic coating and the recyclable capability of NANOCLEAN mirror cup.
The following figure show shows the results of the comparison of the environmental performance of both pieces. Note that since in the first part of the assessment it was confirmed that there were no significant differences between the two scenarios proposed for the Nanoclean mirror cup, in this first figure the comparison between an ABS mirror cup and just one of the scenarios proposed for the Nanoclean mirror cup (worst case) is represented.
High contribution of ozone depletion parameter is due the fluoride composition of paints/coatings.
Deliverables submitted in WP5
D5.1 - Preliminary definition of target specifications - M12.
D5.2 - Results of synergic market surveillance and possibilities of new concept. Analysis and definition of requirements - M24.
D5.3 - Laser workstation for texturing large & complex moulds - M26.
D5.4 - Large-scale micro/nanostructured injection mould and automotive component - M30.
D5.5 - Control of part quality & Technical, economical and environmental assessment - M36
Potential Impact:
First, it is important to identify the position of each partner in the value-chain in order to explain the main impacts of the project. Next Figure shows that all partner of NANOCLEAN project fit perfectly in the value chain of the production of 'self cleaning' 3D components in the chain value.
The NANOCLEAN coordination team really believes that the project has been really successful according to exploitable results that have been achieved. Furthermore, it worthy be remark that some of the results are currently exploiting.
CRF (END USER)
Main impact is focused in the development of new value automotive components with wettability and self-cleaning properties highly competitive with other products of the market (glass/plastic spray coating, coatings by painting Metals and Composites by plasma plastics).
This new technology developed during the project for the production of a prototype (cup-mirror) with a 3D complex geometry can be easy extrapolated to other exterior and interior components of the car. Other parts could be also nano-structured in the future according the market demand. In this case, the self-cleaning property developed in this project it is not in relation with an improvement of the visibility or light transmission of the car mirror or glasses to enhance the user's safety (currently in the market it could be applied some coatings on the glass to get this property). In NANOCLEAN project, the self-cleaning property has been developed for aesthetic purposes. For instance, German market appreciate interior plastic elements of the car in white or lighter colours that easily can get dirty with dust, drinks or even with the impregnated grease of the hands. There is a kind of painted coatings with the same application, but are expensive, less durable and less environmental friendly.
Furthermore this NANOCLEAN technology can be applied not only for car components, but also for industrial and agricultural vehicles, that are exposed daily to ground, water, dirt, etc.
CRF is ready to exploit these results toward FGA and FIAT INDUSTRIAL
UT (DESIGN AND ENGINEERING)
(UT) tried with this research solvent the problem on the application of LIPSS, in the field of surface functionalization, covering the currently gap, that means:
1. Contributing with an available texture portfolio.
2. Knowledge-based processing for improved reproducible.
3. Extended large scale features.
4. Determination, and optimization of quantitative values for irradiation (machining) parameters.
Furthermore, it must be highlighted that UT has carried out a risk assessment based on a modelling study for the mirror-cup mould, due to this kind of assessment is highly demand for industries (including in the 2nd Progress Report)
LIG (ENABLING TECHNOLOGIES)
1. NANOCLEAN project resulted in a unique technology with new capabilities: 3D micro- and nanotexturing. DEM contribution to the development of the workstation.
2. Enabler for new applications in a variety of markets
3. Technology can be integrated into existing manufacturing chains
4. Improve existing products by new functionalities
5. Improve the competitiveness of manufacturing companies in Europe: SME supplier companies and end-user companies.
LIG has achieved the sale of one workstation for micromachining that can be developed supported by NANOCLEAN project.
MAI (DESIGN AND ENGINEERING)
Following exploitable results have been achieved:
1. As exploitable results for NANOCLEAN project can be considered the technical specifications related to the design, build and set-up of the mould and the auxiliary elements needed to obtain thermoplastic injected parts with micro-nanostructured surfaces.
2. MAI will offer to their customers the design and manufacture of moulds and plastic parts with Nanoclean effect, through: Showrooms, technical presentations and commercial quotations.
3. Currently risks identified by MAI could be the scratch resistance for exterior applications (automotive) and the coloured parts.
4. Possible applications are not only limited to automotive sector (front grilles, pillars, fuel caps, interior decorative parts, etc), but also could be applied to white appliances (New markets)
GAI (SUBSYSTEMS TIER 2)
1. Evaluation of self-cleaning / easy-to-clean properties of plastic components represents a promising extension of testing services for wide range of sectors and applications.
2. The suggested testing protocol is considered a good opportunity to customers in consultancy services. Although versatility; the test protocol should be improved and adapted to customers' necessities and potential regulations/normative.
3. In the future it could be considered to contact standardization bodies in order to contribute to the regulation of self-cleaning properties due there is no normative to characterize this property.
BASF (ENABLING TECHNOLOGIES)
In the case of BASF, they get direct exploitation products due to NANOCLEAN project:
1. Material supplier: Direct exploitation. Sell 'new grad' polymer to customers
2. Added value to an 'old' product and Knowhow advantage over competitor
3. Looking for further/other applications based on the 'new material'
4. Transfer gained knowhow to other styrenics
5. Offer customer a solution of an superhydrophobic surface based on styrenics
It is important to remark that 'new material' that will be patent within the results obtained in NANOCLEAN project in the short term.
MAIN CONCLUSIONS
Main exploitable results could be summarising as follows:
- Injection moulding represents a promising technology to develop a nano/microstructured surface with high performances and potentially low costs.
- ASA LURAN S757G an additional hydrophobisation and a flow improving additive, could be a potential material to be up scaled, according its moulding, wettability and mechanical properties. This is a 'new recipe' material for BASF and the mechanics of new material is acceptable for FIAT.
- Within NANOCLEAN improvements of surface in terms of easy-to-clean performances have been demonstrated. An overall testing procedure to evaluate quantitatively the aesthetic and self-cleaning features of standard master flat plaques is set-up. The tests could allow to identify self-cleaning materials and classify (ranking) the samples according to tendency to soiling considering different quantitative parameters. In the future it could be considered to contact standardization bodies in order to contribute to the regulation of self-cleaning properties due there is no normative to characterize this property
- NANOCLEAN is a good opportunity to solve comfort and safety problem with several opportunities in passengers and industrial vehicles.
- Thanks to the value chain established within NANOCLEAN it is possible to target well-established market (having a strong cost-benefits analysis) and emerging markets (with added value).
- TRL is enough high (7-8) for CRF to be transferred to product engineer to select proper components together with NANOCLEAN suppliers.
-NANOCLEAN technology could be also used several applications: biomedical, electronics, white appliances, etc.
- NANOCLEAN technology has demonstrated not only wettability and easy-to-clean properties, but also optical effects that could be used for other applications.
Main conclusions have been exposed: Micro- nanotextures can be applied to 3D curved surfaces, various mould inserts have been machined, textures are durable, preferred mould material has been identified, Knowledge on mould design for textured surfaces has been gained, working 3D texturing technology will enable numerous new applications (valuable exploitable result): wetting, friction and lubrication from engine parts, manipulation of light for optical effects and manipulation of cell adhesion for biomedical purposes.
SOCIO-ECNOMICAL IMPACT
Furthermore, social impact achieved has been considered relevant, due to the creation of employment and the development of practices for students and a Master Thesis.
NanoClean is the basis for writing one phd thesis (UT). The Results of NanoClean and the thesis can also be used as a basis for practical assignments and lectures in master and bachelor courses.
Furthermore, 2 six-monthly contracts of practices after the Degree have been carried out in CRF.
It must be remarkable the significantly staff increment of the spin-off LIG (3 new employees). LIG has been created 3 new contract employments due to NANOCLEAN project. This project has constituted a key support for the taking-off of a spin-off (LIG).
MAI expect that with the obtained results can increase its services in the medium term and the development and fabrication of automotive components with high added value for new European customers, acting like an economic engine.
Name of the scientific representative of the project's co-ordinator : Monica Solay
Title and Organisation: Maier S. Coop.
Tel: +0034- 946-259200
Fax: 946-259219
E-mail: monsol@maier.maier.es
Project website: http://www.nanoclean-project.eu