Keeping black plastics out of the landfill
One of the many problems with plastics is that it is difficult to determine which plastic is recyclable and which is not. For example, coloured-shredded plastic pieces can be automatically recognised using near-infrared spectroscopy (NIRS) and then sorted and recycled. Unfortunately, NIRS is unable to detect the additives that make a plastic non-recyclable and that are often found in the black plastics used in appliances, electronic devices and vehicles. As a consequence, black plastics tend to end up in the landfill or are incinerated. The key is to be able to quickly identify the polymer and any restricted additives that make it non-recyclable. Diamatex, an Italian technology start-up, thinks they may have a solution. Through the support of the EU-funded SELEX project, they are developing a handheld X-ray device that can identify polymers in black and coloured plastics, fillers and additives. “Black plastics represent an important and growing fraction of WEEE and automotive waste,” says Danilo Pacella, a researcher at Diamatex. “Now, there is an effective and easy way to sort the recyclable from the non-recyclable material, which will ultimately result in less plastic ending up in landfills.”
An easy-to-use solution
SELEX uses soft X-rays to discriminate black plastics. “The patented, handheld device combines X-ray transmission, absorption and fluorescence to identify and quantify polymers, fillers and additives,” explains Pacella. Called Stimulated X-ray Ecofluorometry, Pacella notes that the technique can be used with any type of transparent, coloured or black plastic without the need for a previous treatment of the sample. “The first prototype we developed is a portable device that does not require any special technical skills or competences,” adds Pacella. “Once the plastic piece is placed inside the device, a full quantitative analysis of the component is automatically performed in just one second.” Although the system itself is simple to use, developing it was anything but. According to Pacella, the project faced many challenges. “We had to process tests and studies for nearly 3 years before we could fully comprehend the physical processes and mechanisms in the materials and know how to best exploit them,” he says. But the team persevered, ultimately producing an accurate, flexible and highly sensitive technique for automatically analysing materials.
An array of potential uses
Although SELEX was originally developed for analysing and recycling black plastics, it has since been expanded to other recyclable materials, including glass, wood and metals. The technique can also be placed onto a conveyer belt to automatically analyse and sort the pieces moving under it. “We’ve also demonstrated that SELEX can be used not only for solid material, but also with grains, powder and liquids, opening the possibility for its use in the food sector for detecting impurities or for compliance analysis,” concludes Pacella. “We’ve even used it to test for counterfeit leather products.” The SELEX device is currently undergoing final engineering, after which it will be available for sale. The company is also working to further standardise the technique and is exploring expanding its use to other sectors and applications.
Keywords
SELEX, plastics, X-ray, recyclable, polymer, additives, WEEE