Synthesis of unsaturated polyesters from post-consumer pet bottles

Abstract

Unsaturated polyesters synthesized from post-consumer PET bottles was studied in this work. PET was depolymerized by glycolysis in excess mixture of ethylene glycol and propylene glycol at 190-200ํC in the presence of zinc acetate as catalyst. Glycolyzed product was reacted with maleic acid to form unsaturated polyester. Study was done on the following factor which have effects on the properties of glycolyzed product and unsaturated polyesters, that is depolymerization time and molar ratio of mixture of ethylene glycol and propylene glycol and PET (EG+PG)/PET). It was found that impact strength and hardness of unsaturated polyester increased with depolymerization time, these effect come from the increasing amount of monomers in glycolyzed product and cross-linking between chains. At low molar ratio of (EG+PG)/PET, hardness increased, and then decreased at high molar ratio of (EG+PG)/PET. The amount of monomers in glycolyzed product, cross-linking between chains and remained glycol, all enhance the hardness.