Recycling of thermoplastic materials: Development of a self-adaptive process to the recycled materials

Over the last few decades, thermoplastic polymers have become increasingly popular and widely used materials in our lives. However, these mass consumptions remain difficult to reuse. Although mechanical recycling is being seriously proposed as an alternative solution [1], until now many obstacles prevent its application to polymers. Undetermined initial properties and aging conditions of post-consumer waste, which are, in fact, extremely variable, result in an ignorance of the aged material rheological properties before their reprocessing. As a consequence, the adjustment of extrusion parameters becomes very difficult and can vary over time and between supply batches. In this context, the project RECYPLAST-DEMO was proposed aiming at developing a prototype able to characterize, in real-time [2], the rheological properties of extruded waste materials and self-adjust the operating parameters of the machine, with the help of artificial intelligence, to maintain products of required quality. Our work concerns inline rheological characterization of materials using an instrumented die numerically tested with the software POLYFLOW (R) for the viscosity range of a PP, designed and experimentally validated in a later step of the project. The goal is to obtain the rheological behavior of the material from pressure difference measurements along the length of the developed die and assess data compared to rheological characterization measurements performed in laboratory on virgin material and aged ones. This paper highlights the effect of the processing temperature and the residence time on the aging of the polymer. Moreover, the numerical work of the developed extrusion die is presented and explained.