Investigation of polyethylene terephthalate synthesis via solution polymerization technique

Abstract

Poly (ethylene terephthalate) (PET) is a thermoplastic polyester commonly used in the industry owing to its good mechanical strength, thermal stability, high solvent resistance and low-cost production. According to application area, various molecular weight PET is produced mostly at high temperature at melt phase under vacuum. Although melt polymerization is feasible and widely used, there are disadvantages of the system such as degradation of PET due to the long reaction time at high temperature and formation of side products such as diethylene glycol. To avoid such degradations, melt polymerization is used to obtain PET’s that are considered medium molecular weights then solid state polymerization is employed to produce higher molecular weight PET’s. However, SSP requires very long reaction times (12-24 h) which makes it very inconvenient and expensive. Therefore, in the present work, an alternative pathway that could potentially replace the SSP process was investigated. The main goal was to synthesize PET-anhydrides, in other words, polyester anhydrides, that may act as chain extenders when reacted with –OH terminated medium molecular weight PET’s. During such effort, syntheses of polyacid anhydrides, then PET polyesters, then finally PET polyester anhydrides were investigated. These reactions were all carried out by solution polymerization techniques which is not a reported technique for the synthesis of PET. The scope and the limitation of such a process for the synthesis, and its effect on the final polymer properties are discussed. The results from templatize chain coupling reactions of PET using the polyanhydrides and polyester anhydrides is presented.