Kinetic and thermodynamic studies of depolymerisation of poly(ethylene terephthalate) by saponification reaction

Abstract Depolymerisation reaction of polyester waste was carried out by a saponification reaction. Yields of depolymerised products were up to 85% for a 2.5‐h reaction time. Products obtained were characterized by chemical as well as instrumental analysis such as mp (sublimation), acid value and FTIR spectra. The valued obtained for terephthalic acid (TPA) agreed with those for the pure substance. Chemical kinetics of this reaction shows that it is a first‐order reaction with respect to poly(ethylene terephthalate) (PET) concentration with a velocity constant of the order of 10 −2 min −1 . In the light of the Yashioka modified shrinking core model, a simultaneous fragmentation and depolymerisation model was proposed for the kinetics of hydrolysis of PET. The modified model is based on change in acid value of the product obtained, which is directly related to the change in surface area of particle. The energy of activation and the Arrhenius constant (frequency factor) obtained by Arrhenius plot were 59.71 kJ g −1 and 8.325 × 10 6 min −1 respectively. © 2002 Society of Chemical Industry