Four major phenolic compounds, o-cresol, 2, 6-xylenol, 2, 4-xylenol and 2, 4, 6-trimethyl-phenol were obtained as monomeric scission products from thermal degradation of poly (oxy-2, 6-dimethyl-1, 4-phenylene) (polyphenylene ether or PPE) in an inert atmosphere. The dimeric scission products were more complicated than the monomeric products. The quantitative analysis of both scission products were took into accounts so as to elucidate the degradation mechanism. The chemical structures of the scission products suggested that the ether bridges on the main chain are partially converted to methylene bridge to form C-C bonds prior to the thermal degradation. The composition can be explained by the cleavage of the C-C bonds in almost equal probability. The structure of the aged polymer is much more relevant to the thermal degradation mechanism than that of the polymer just after prepared in the case of the thermal degradation of PPE.

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The weatherability of polyvinyl chloride (PVC) was evaluated in detail as a function of film thickness. PVC films were prepared with a test roll after mixing PVC powder with plasticizer and stabilizer. The films were exposed to daylight and examined mechanical properties, color difference and transmittance of visible light. At the same time, the content of stabilizer was determined as a function of exposure days. The decrease of mechanical strength was faster in thin film than in thick one. On the contrary to the elongation, the elastic modulus and tear strength increased with exposure days. The color difference per unit thickness also increased with exposure days. These properties changed more considerably in thinner film. The changes of mechanical properties can be mainly attributed to the decrease of plasticizer in films. Further, the surface analysis by XPS was carried out and the increase of oxygen content with exposure days was confirmed. However, the decrease of chlorine was not large in 400 exposure days even on the surface.

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