Evaluation and identification of degradative processes in post-consumer recycled high-density polyethylene

We have studied the degradation resulting from reprocessing of post-consumer HDPE in order to verify its re-stabilization needs. Cone-plate rheometry was used to provide information about the molar mass and the molar mass distribution after reprocessing and stabilizing the material. Infrared spectroscopy (FTIR), oxidation induction time (OIT), melt flow index (MFI) and cone-plate rheometry measurements were performed. Also, atomic absorption spectrophotometry tests were carried out to verify which catalytic residue was present in the recycled HDPE so as to correlate it to the degradation processes taking place in the polymer. The results showed that in this case the post-consumer HDPE displayed cross-linking when reprocessed, indicating the need for re-stabilization. They also showed that the use of 0.2% antioxidant was efficient in blocking these processes, and that the cone-plate rheometry technique was powerful in assessing degradative processes. (C) 2003 Elsevier Science Ltd., All rights reserved.