REACTIONS INDUCED BY TRIPHENYL PHOSPHITE ADDITION DURING MELT MIXING OF PET PBT BLENDS - CHROMATOGRAPHIC EVIDENCE OF A MOLECULAR-WEIGHT INCREASE DUE TO THE CREATION OF BONDS OF 2 DIFFERENT NATURES/

A detailed chromatographic investigation has been carried out on the i nfluence of triphenyl phosphite addition in molten poly(ethylene terep hthalate) or poly(ethylene terephthalate)/poly(butylene terephthalate) blends. The observed molecular weight evolution corresponds to torque and viscosity observations and fully confirms the occurrence of high temperature reactions between polyester and phosphite. The reaction me chanisms deduced from model compound studies are successfully applied to polymers. The formation of bonds of different types is verified: ph osphite reactions with hydroxyl chain ends lead to the incorporation o f significant quantities of phosphorus into the polyester backbone. A high sensitivity of these phosphorus containing links towards water, p henol or m-cresol has been observed. Subsequent carboxyl chain end att ack on the phosphorus linkages leads to stable ester bonds. (C) 1997 E lsevier Science.