Thermal Stability and Thermal Degradation Kinetics of Poly(Trimethylene-co-Butylene Terephthalate) Copolymers

Abstract

The thermal stability and thermal decomposition kinetics of poly(trimethylene-co-butylene terephthalate) (PTBT) copolymers in nitrogen were studied by means of thermogravimetry. The PTBT copolymers had good thermal stability in nitrogen and the introduction of copolymer component had a slight influence on the thermal stability of copolymers. The mass loss of PTBT copolymer was accomplished in one main mass loss stage and one small weight loss in the early stage of decomposition. The PTBT copolymers started to decompose at ≈350.0°C and completed decomposition at ≈440.0°C with the heating rate of 5°C/min. The characteristic degradation temperatures of PTBT copolymers shifted toward higher temperatures with increasing heating rates and poly(trimethylene terephthalate (PTT) content. Furthermore, various degradation methods, including the Ozawa–Flynn–Wall method, Friedman's method, and Kissinger's method, were used to determine the activation energies of copolymers. The three methods were applicable to the kinetic description of thermal degradation of PTBT copolymers. The thermal activation energies obtained by three methods were in satisfactory conformity. The thermal degradation kinetics of copolymers could be interpreted in terms of multi-step degradation mechanisms. It was shown that the thermal stability of PTBT copolymers increased with increase in PTT content. Copolymers with higher PTT content showed higher degradation temperature and thermal activation energy. A general activation energy range of 180–200 kJ/mol was suggested for the processing and use of PTBT copolymer fibers.

Keywords:

• activation energy
• copolymers
• poly(butylene terephthalate) (PBT)
• poly(trimethylene terephthalate)(PTT)
• TGA
• thermal degradation kinetics