Effect of post-polymerization on the crystallization and melting behavior of poly(butylene terephthalate)

Abstract

In this paper, the chemical and physical structures of poly (butylene terephthalate) (PBT) after different thermal treatments, in the range of 180–260 °C and up to 10 h, were systematically investigated. Nuclear magnetic resonance and Fourier transform infrared spectroscopy results showed that the chemical structure of PBT did not change significantly after treatment. The thermal stability of the heat-treated samples, reflected by the decomposition temperature shown in thermogravimetric analysis, was the same as that of the untreated samples. During the treatment, the molecular weight increased, while the polydispersity remained essentially constant (∼2). The highest increase in molecular weight was observed when the samples were subjected to heat treatment near the melting point temperature (220 °C). Importantly, the crystallization temperature of the samples changed with heat treatment temperatures and times, while the melting point remained essentially constant.