取代二苯基脲对PVC的热稳定作用——性能递变规律与机理

Heat Stabilization of Substituted Diphenylureas on PVC—Progressive Change Law of Performance and Mechanism

用烘箱变色法研究了几种取代二苯基脲对聚氯乙烯(PVC)的热稳定性能。结果表明,取代二苯基脲均具有类似于硬脂酸锌的热稳定特性,属于初效型主热稳定剂,与硬脂酸钙(CaSt2)和环氧大豆油并用存在着明显的协同效应;取代二苯基脲的热稳定性能随其分子中与尿母核相连基团的吸电子性的增强而提高;根据其热稳定性能递变规律可以推测出取代二苯基脲是通过其羰基C原子作为亲电原子与PVC发生亲电反应而发挥热稳定作用的,传统的Frye和Horst理论不适用于取代二苯基脲。

The performances of heat stabilization of several substituted diphenylureas on PVC were studied by oven discoloration method. It was shown that the substituted diphenylureas were initialterm effective type primary heat stabilizers showing characteristics of heat stabilization similar to zinc stearate and remarkable synergistic effects with calcium stearate and epoxidized soybean oil; the heat stabilizing performance of substituted diphenylureas improved with increasing electronattracting ability of the groups linked to the urea moiety of the molecules. Based on this heat stabilizing behavior, it could be speculated that substituted diphenylureas stabilized PVC by electrophilic reaction with PVC using their carbonyl carbon atoms as a electrophilic atom. This meant that the traditional Frye and Horst＇s theory on mechanism of heat stabilization of heat stabilizers did not apply to, substituted diphenylureas, and therefore, the exact mechanism of heat stabilization of heat stabilizers needed to be clarified by further research.