PET recycling: Evaluation of the solid state polymerization process

Many studies have been carried out to make bottle-to-bottle recycling feasible. One of the difficulties found is the decrease in the polymer's molar mass, which damages the injection blow molding process. A method usually employed to increase the molar mass of virgin PET consists of solid-state polymerization (SSP). In this work, we studied the SSP process applied to post-consumer recycled PET by analyzing the inherent viscosity and amount of carboxylic end groups, and the results of dynamic flow rheometry. Although the results show that the recycling process decreases polymer molar mass, and this indicates degradative processes, SSP was successful in increasing molar mass in post-consumer recycled PET. This made feasible bottle-to-bottle recycling. In addition, the parallel plate rheometry technique was powerful in assessing the degradative process and, therefore, that the SSP process was successful.