Efficient recycling process is of high importance to reduce the amount of plastics being dumped in the landfills. Currently, it is not economically viable to sort plastics to enable their recycling. Many plastics, for example, contain flame retardants to resist ignition, reduce flame spreading, minimize smoke formation, and prevent them from dripping.
Quantity and types of flame retardants added to plastics may vary considerably, due to the need to tailor the plastic to its specific applications as well as to meet the safety standards. However, same type of plastics containing similar flame retardants can be recycled together.
Therefore, before initiating the recycling process, plastics are required to be sorted, not only by the type but also by any flame retardant added. Recycling of plastics cannot take place without sorting, a study reported.
In a new approach, researchers have developed a method using chemometrics and near infrared hyperspectral imaging that can sort between different types of plastic such as acrylonitrile butadiene styrene and polystyrene, and also between different additions of flame retardants.
Lead researcher Jose Amigo and colleagues described the new method in a research paper published in the Journal of Spectral Imaging (JSI).
Hyperspectral imaging is used to collect an image of an area, and simultaneously a spectrum for every individual pixel of that image. Chemometrics, on the other hand, is a data analysis technique that can find hidden patterns within data and help construct a model which allows the identification of image parts by their chemical composition.
For the recycling application, it is important to use an imaging technique, according to the researchers, as it can classify individual pieces of plastic and any type of flame retardant present in those plastics. Many researchers have studied about recycling plastics for many years, and few commercial cameras that can separate a limited number of plastic types were available for some time, Jose Amigo said.
However, in the new project, the researchers wanted to move a step ahead to separate plastics containing flame retardants. In addition, they evaluated the newly proposed method using real samples that can be found in existing recycling lines.