This study of the thermal breakdown of copolymers of n-butyl acrylate and methyl methacrylate represents a further contribution to the establishment of a comprehensive picture of the degradation of acrylate-methacrylate copolymer systems. A series of copolymers covering the whole composition range was synthesised. Degradations were carried out under vacuum either in a dynamic molecular still or using a new technique developed in these laboratories. Thermal methods of analysis such as thermogravimetric analysis (T. G. A.) and thermal volatilization analysis (T. V. A.) showed that the copolymers became more stable to thermal breakdown as the acrylate content was increased. These techniques allowed a suitable temperature range to be chosen in which to study the decomposition isothermally. The gaseous degradation products, liquid products, chain fragments and residue were each examined separately, using, among other techniques, infra-red spectroscopy, gas-liquid chromatography, mass spectrometry and combined gas chromatography-mass spectrometry. The complex nature of the pyrolysis of this copolymer system is reflected by the great variety of products obtained. The main gaseous products were found to be carbon dioxide and but-1-ene, while the most important liquid products are methyl methacrylate and n-butanol. Quantitative measurements enabled the build up of these products to be followed as degradation proceeds, and mass balance tables were drawn up for each copolymer studied. Pyrolysis was carried out mainly at 31
