2010 Volume 22 Issue 2 Pages 54-58
Degradation occurs at different temperature when the heating rate is changed. This heating rate depend-ence of the degradation temperature (Td) is quite natural from a point of view of physical chemistry. When the Td was plotted again the heating rate in a semi-logarithmic scale, a linear straight line was generally obtained. (1) This straight line shifted toward downward, when oxygen existed in an atmosphere. The ex-tent of the shift was closely related to the type of degradation pattern (random scission, depolymerization) of each polymer. It was in the following order : isotactic PP>PE>PSt>PMMA>P (aM) St. Thus, oxygen showed a degradation promoting effect, the extent of which was larger in the former than in the latter polymer. (2) In the case of elimination type of polymers (PVC, PVA), however, two lines crossed over in this temperature region. (3) In the case of reaction of side groups (PAN), further, the latter line shifted toward upward di-rection. That is, oxygen showed a remarkable retarding effect. We can designate these oxidative degrada-tion pattern : parallel (−), cross-over type, and parallel (+) type-relationship.
