Advancing plastics recycling: A transdisciplinary approach to the development of characterisation methods for secondary plastics

The actual process of recycling plastics usually involves several operations, such as separation, sorting, cleaning, grinding, feeding (dosing), and above all compounding. A common feature of all these operations is the requirement of conveying raw materials from one point to another within one piece of process equipment or from one piece of process equipment to another. Depending on the operation at hand, the repeatability requirements of the conveying performance may vary from low to very high. The quality of plastic recompounds is directly dependent on the respective compounding process, which requires constant and repeatable conveying performance of the raw materials. However, after shredding, secondary raw materials, such as regrinds, flakes and fibre agglomerates, usually have wide particle shapes and size distributions. This makes it difficult to convey secondary plastic materials because they defy conventional theoretical considerations of bulk solids flow behaviour and associated design calculations. This research aims to bridge this gap by developing characterization methods for secondary plastics based on fundamental research on the flow behaviour of flakes, fibres and regrind materials. By employing a transdisciplinary approach, knowledge from stakeholders will be channelled into the method development and validation phases to ensure practical applicability.