COMPETITION BETWEEN DEGRADATION AND CHAIN EXTENSION DURING PROCESSINGOF RECLAIMED POLY(ETHYLENE-TEREPHTHALATE)

During processing of poly(ethylene terephthalate) (PET) hydrolytic cha in scission, induced by the presence of small amounts of water, is the main cause of degradation. During repeated reprocessing chain scissio n can also occur because of the presence of other polymeric contaminan ts like PVC. In order to avoid or to limit hydrolytic chain cleavage a dequate drying of PET before melt processing is necessary. Of course t his practice is even more recommended when repeated processing steps a re used, as for PET recycling. The behavior of recycling PET obtained from post-consumer water bottles when treated in a melt mixer under di fferent conditions has been investigated in order to better understand the processing conditions that can reduce or avoid the hydrolytic cha in scission. During processing both degradation (chain scission) and c hain extension occur. When the processing is carried out under a nitro gen atmosphere the latter mechanism prevails leading to a polymer havi ng larger molecular weight. (C) 1998 Elsevier Science Limited. All rig hts reserved.