Heat Stabilizing Performance of Substituted Phenyl(thio)ureas on PVC and It's Progressive Change Law
The performances of heat stabilization of several substituted phenyl ( thio) ureas on PVC were studied. It was shown that:l) 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 carbonyl 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.
substituted phenylureassubstituted phenylthioureaspoly( vinyl chloride)heat stabilizerperformance of heat stabilization
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