Characterization of Properties and Kinetic Analysis of Unsaturated Polyester Resin Synthesized from PET Alcoholysis Waste

Recycling and reutilization of waste PET through alcoholysis has been a prominent focus of current research. However, the alcoholysis process is reversible, leading to the generation of oligomeric waste byproducts. To further utilize these wastes, this paper processed oligomeric waste derived from various alcoholysis systems to synthesize unsaturated polyester resins (UPRs). The fundamental characteristics, mechanical properties, and curing processes of synthesized UPRs were analyzed based on GPC, FTIR, TG, tensile testing, DMA, and DSC tests. The results indicate that wastes were successfully synthesized to UPRs. The UPRs synthesized from ethylene glycol (EG) and diethylene glycol (DEG) possess more complex compositions; among these, the UPR synthesized from EG exhibited higher thermal stability, whereas the UPR synthesized from DEG showed a broader molecular weight distribution and a lower glass transition temperature (<i>T_g</i>). In addition, the UPR synthesized from DEG exhibited a remarkably high elongation at break (>180%), potentially attributed to its long molecular chains. Regarding curing characteristics, UPRs obtained from DEG and propylene glycol (PG) exhibited slower curing rates and demanded higher activation energies. Moreover, the curing processes of UPRs could be well described by the Sesták-Berggren autocatalytic model.