Influence of thermal degradation on the crystallization of poly(butylene terephthalate)

• Published in: Express polymer letters Vol. 18; no. 3; pp. 309 - 325
• Main Authors: Nasr, Ahmed, Svoboda, Petr
• Format: Journal Article
• Language: English
• Published: Budapest Budapest University of Technology and Economics, Faculty of Mechanical Engineering, Department of Polymer Engineering 01-03-2024; Budapest University of Technology
• Subjects: Annealing; aromatic polyesters; Cooling; crystallinity; Crystallization; degradation; differential scanning calorimetry; Engineering; Influence; kinetics; Materials science; Melting points; Molecular weight; Nitrogen; Polybutylene terephthalates; Polymers; Temperature; Terephthalate; Thermal degradation; x-ray; X-ray scattering; Czech Republic
• ISSN: 1788-618X; 1788-618X
• DOI: 10.3144/expresspolymlett.2024.22

Our work reveals a notable shift in the crystallization temperature (Tc) of poly(butylene terephthalate) (PBT) at which crystallization occurs due to exposure to prolonged thermal degradation at 270 °C in an environment of nitrogen gas. The initial Tc of 193 °C undergoes a marked decrease, settling at 133 °C, which signifies a considerable 60 °C shift towards lower temperature ranges. This transition is discernible across three distinct degradation stages: an initial phase of increase, an intermediate phase characterized by a sharp decline, and a subsequent late stage of the degradation phase characterized by a more moderate decrease in Tc. Both crystallinity and crystallization kinetics consistently mirror this pattern, demonstrating an initial rise, a rapid subsequent drop, and a gradual decline in the late-stage period. Evident from the presence of two melting peaks, the research implies differing lamellar thicknesses. As the degradation progresses, the melting points of these peaks, denoted as 7m| and Tmi, decline at 38 and 41 °C, respectively. Validation of the degradation-induced changes is provided by a small angle X-ray scattering (SAXS), which corroborates the observed decrease in the long period (L). A contextualization of the results against prior studies underscores analogous trends in the alteration of crystallization behaviour consequent to degradation.