取代苯基(硫)脲对PVC的热稳定性能及其递变规律

Heat Stabilizing Performance of Substituted Phenyl(thio)ureas on PVC and It's Progressive Change Law

研究几种取代苯基(硫)脲对PVC的热稳定性能,结果表明:1)取代苯基(硫)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;2)取代苯基(硫)脲的热稳定性能随羰基C原子上所连接基团拉电子性的增强而提高。根据这一热稳定性能递变规律可以推测,取代苯基(硫)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。这就意味着,关于热稳定剂作用机理的传统Frye和Horst理论至少不适用于取代苯基(硫)脲。因此,热稳定剂的确切作用机理还需进一步地研究加以阐明。

The performances of heat stabilization of several substituted phenyl （thio）ureas on PVC were studied. It was shown that： 1 ） the substituted phenyl（thio） ureas erre initial-term effective type primary heat stabilizers showing characteristics of heat stabilization similar to zinc stearate and remarkable synergitic effects with calcium stearate and epoxidized soybean oil. 2） the heat stabilizing performance of substituted phenyl（thio） ureas improved with increase of electron-drawing ability of the groups linked to the earbonyl carbon atom. According to this progressive change law of heat stabilizing performance,it could be speculated that substituted phenyl （thio）ureas stabilize PVC by electrophilic reaction with PVC using their carbonyl carbon atoms as a electrophilic atom. It means that the traditional Frye and Horst＇s theory on mechanism of heat stabilization of heat stabilizers did not apply to, at least, substituted phenyl（thio） ureas, and therefore, the exact mechanism of heat stabilization of heat stabilizers need to be clarified by further research.