红泥聚氯乙烯复合材料热稳定性的机理

各种红泥对PVC都有优良热稳定作用,其热稳定性机理为:1)红泥中的基因Al-O能与PVC分子链上的活泼叔碳氢及—CO—CH=CH—CHCl—基团中的活泼氯发生取代反应消除PVC链上易脱HCl的始发点,从而使PVC链稳定;2)红泥中的游离碱、碱性金属氧化物与碱性金属盐能及时与PVC初脱出来的HCl起反应或吸收,从而阻止PVC继续分解HCl;3)红泥中的铁组分不论以FeCl_3或Fe_2O_3存在,都有显著加速PVC热分解速度,其作用机理可能是Fe_2O_3能促进PVC链生成反常结构-CO-CH=CH-CHCl-,它是促使PVC易脱HCl的一个主要反常结构因素。

The Mechanism of Thermal Stability of RM-PVC Composite

In this paper, the following results have been obtained. (1). The chemical bond Al-O of Red mud can react by substitution with the reactive H-atom in tertiary carbon and with the reactive Cl-atom in the group -COCH = CHCHCl- of PVC chain in order to eliminate these unstable sites in PVC chain which are easy to liberate HC1. And consequently, the PVC chain will become stable. (2). The free base, basic oxides and basic metalic salts in Red Mud can immediately combine or absorb HC1 liberated from PVC to prevent it to liberate further. (3). Either FeCl3 or Fe2O3 can promote the rate of thermal decomposition of PVC, the mechanism of which is probably due to the production of abnormal structure -COCH=CHCHCl- in PVC Chain by Fe2O3. It is one of the important abnormal structures to make PVC liberate HCl easily under heating.