Chemical transformation of pet waste through glycolysis

PET bottle grade material makes up a significant portion of the feedstock in plastics recycling. Theoretically, there are many end users however there are few applications for less purified grades of recycled PET. The current work is aiming to investigate the transformation of recycled PET into its chemical building blocks using glycolysis to produce unsaturated polyester resin. In this regard, PET waste has been collected from different sources, mainly, beverages and bottled water. Chemical transformation has been achieved through degrading glycolysis reaction with different glycols namely, propylene glycol, diethylene glycol, triethylene glycol and mixture of diethylene glycol with propylene glycol or triethylene glycol in equal amounts. The glycolized products have been converted into unsaturated polyester (UP) after the reaction with maleic anhydride. Finally, styrene was added as a crosslinker and the obtained UP has been characterized. Factors affecting the curing process of the obtained unsaturated polyester resin have been investigated.

Schematic diagram for recycling of PET wastes into unsaturated polyester.Figure optionsDownload as PowerPoint slideHighlights
► Resins based on recycled PET can help reduce the end products cost and pollution.
► Glycolysis leads to formation of oligomers ended with free OH groups.
► PG is of higher activity with high tendency to degrade PET into free OH chain ends.
► PG-based UP showed higher overall rate of crosslinking than the other matrices.
► Time to reach maximum temperature depends inversely on styrene % and glycol type.