The thermal degradation mechanism and kinetic analysis of hydrogenated bisphenol-A polycarbonate

Hydrogenated bisphenol-A polycarbonate (PHBPA) was successfully synthesized from dimethyl carbonate (DMC) and hydrogenated bisphenol-A (HBPA) by the method of two-step polycondensation. The chemical structure and the molecular weight of PHBPA was identified by(1)H-NMR spectra and gel permeation chromatography (GPC), respectively. In order to analyze the thermal degradation mechanism of PHBPA, a non-isothermal pyrolysis process was conducted and the violate products were detected using Fourier-transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS). There were some reactions occurred during the pyrolysis including decarboxylation, disproportionation of the C-H transfer and beta-H transfer, and the Fries rearrangement. In addition, the well-known Flynne-Walle-Ozawa (FWO) and Coats-Redfern kinetic analysis methods were used to calculate the values of activation energy and pre-exponential factors. Furthermore, isothermal pyrolysis experiments were performed and revealed that the reaction of decarboxylation occurred at 225 degrees C. This decarboxylation suggests that the molecular chain of PHBPA does not easily grow to a high-molecular-weight polymer.