DEGRADATION STUDIES OF SOME POLYESTERS AND POLYCARBONATES .8. BISPHENOL A POLYCARBONATE

The thermal degradation of bisphenol A polycarbonate has been studied using thermal volatilisation analysis (TVA), thermogravimetry and differential scanning calorimetry. A detailed investigation of the various decomposition products has been made, using subambient TVA, IR spectroscopy, mass spectrometry and GC-MS techniques. The degradation behaviour, when the polymer is heated under continuous evacuation, is explained on the basis of the results obtained. Under programmed heating, the polymer is stable up to over 300-degrees-C and the main decomposition process is observed with a rate maximum around 460-degrees-C. There is a considerable solid residue of decomposition at 500-degrees-C and the main products of decomposition consist of cyclic dimer plus bisphenol A, together with smaller amounts of volatile products including carbon dioxide, p-cresol, p-ethyl phenol, phenol, p-vinyl phenol, p-isopropyl phenol, carbon monoxide and methane. No evidence has been found to support the argument presented previously that the initial stage in the degradation involves hydrolysis. The nature and wide range of products suggests that the decomposition in the absence of air and moisture probably proceeds mainly by homolysis of the polymer chain and reactions of the radicals so formed, rather than by ester interchange.