Partially bio-based copolyesters poly(ethylene 2,5-thiophenedicarboxylate-co-ethylene terephthalate): Synthesis and properties

The aim of this study was to investigate the feasibility of replacing petroleum-based terephthalic acid (PTA) with renewable 2,5-thiophenedicarboxylic acid (TDCA) in poly(ethylene terephthalate) (PET), a series of copolyesters were synthesized from PTA, TDCA and ethylene glycol (EG). The effects of composition on structures, thermal properties, mechanical properties and beta relaxation were studied. With the increase of the TDCA content, the esterification reaction time is noticeably shorter in the first step because the acidity of TDCA is stronger. PET, PETF and PETTF25 are semi-crystalline materials. However, no melting and crystallization peaks were observed for PETTF49 and PETTF74. All polyesters exhibit high tensile strength (56.0-68.8 MPa) and good toughness (elongation at break: 190-508%). With the increase of the TDCA content, beta relaxation peak is shifted to a higher temperature. For all PET, PETF, and PETTFs, high peak intensity of the beta relaxation can be achieved, indicating that the motions of more units are believed to contribute to the relaxation behavior. (C) 2020 Elsevier Ltd. All rights reserved.