Synthesis of unsaturated polyester resin from postconsumer PET bottles: Effect of type of glycol on characteristics of unsaturated polyester resin

Postconsumer PET bottles including water and soft-drink bottles were depolymerized by glycolysis in excess glycols, such as ethylene glycol, propylene glycol, and diethylene glycol, in the presence of a zinc acetate catalyst. The obtained glycolyzed products were reacted with maleic anhydride and mixed with a styrene monomer to prepare unsaturated polyester (UPE) resins. These resins were cured using methyl ethyl ketone peroxide (MEKPO) as an initiator and cobalt octoate as an accelerator. The physical and mechanical properties of the cured samples were investigated. It was found that the type of glycol used in glycolysis had a significant effect on the characteristics of the uncured and cured UPE resins. Uncured EG-based UPE resin was a soft solid at room temperature, whereas uncured PG- and DEG-based resins were viscous liquids. In the case of the cured resins, the EG-based product exhibited characteristics of a hard and brittle plastic, while the PG-based product did not. The DEG-based product exhibited characteristics of hard and brittle plastic after strain-induced crystallization had occurred. In addition, it was also found that no separation of the type of bottles was needed before glycolysis, since UPE resins prepared from water bottles, soft-drink bottles, and a mixture of both bottles showed the same characteristics. (C) 2003 Wiley Periodicals, Inc.