氨基脲嘧啶对PVC的热稳定作用——性能递变规律与机理

Heat Stabilization Effect of Aminouracils on Poly(vinyl chloride)—Progressive Change Law of Performance and Mechanism

用烘箱变色法测试了几种6-氨基尿嘧啶对聚氯乙烯(PVC)的热稳定作用。结果表明,其热稳定性能随分子中与脲基N原子相连基团的吸电子性的增强而提高;根据这一热稳定性能递变规律和分子结构特点可以推测,6-氨基脲嘧啶是通过6-C原子作为亲电中心与PVC发生亲电反应而产生热稳定作用的;Frye和Horst所提出的传统热稳定剂作用机理(不稳定氯取代)不适用于6-氨基脲嘧啶,热稳定剂的确切作用机理还需进一步的研究加以阐明。

Effects of several 6-aminouracils on heat stability of PVC were investigated by an oven discoloration method.The results indicated that the heat stability of PVC was improved with an increase of electron-withdrawing capability of groups linked to the carbamido groups.Based on this progressive change law of heat stability as well as molecular structural characteristics of 6-aminouracils,it was predicted that 6-aminouracils could stabilize PVC by an electrophilic reaction with PVC through their 6-C atom as the electrophilic center.This means that the classical Frye and Horst＇s theory are not suitable for the heat stabilization mechanism of 6-aminouracils,and therefore,the exact mechanisms for this new heat stabilizer should be clarified in further work.