PVC/CaCO_3热降解过程及多元醇对PVC的热稳定作用

Study on Course of Thermal Degradation of PVC Blend and Thermal Stabilization of Polyols in PVC

利用热失重一红外光谱联机（TG-FTIR）分析技术研究了PVC／CaCO3共混物在氮气气氛下、30-900℃范围内的热降解行为。结果表明：PVC共混物的热降解过程可分为3个阶段，分别在170-380℃，380-570℃和570-758℃范围内。其中，第一阶段主要为PVC脱HCl反应阶段，热降解产物主要为HCl：第二阶段主要为共轭多烯结构的裂解和环化，产物为低烃类化合物、苯及其衍生物；第三阶段为碳酸钙的分解反应。产物为CO2。研究了几种多元醇化合物对PVC的热稳定作用，发现双季戊四醇与硬脂酸钙、硬脂酸锌之间的协同作用最好，其添加量愈多，共混物的稳定性愈好。

The thermal degradation of polyvinyl chloride （PVC） blend under high temperature and nitro- gen atmosphere was investigated by TG-FTIR analyzing technology. The results show that the thermal degra- dation of PVC blend takes place in three temperature ranges, namely 170-380 ℃, 380-570℃ and 570-758℃. The first stage is dehydrochlorination of PVC, the main pyrolysis product is HC1; the second stage is py- rolysis and cyclization of conjugated polyene, the main pyrolysis product is low molecular weight hydrocarbon, benzene and its derivatives; the third stage is decomposition of calcium carbonate, the main product is carbon dioxide. In this paper we studied the stability of different polyols. They can effectively improve the thermal stability of PVC. There is good synergistic effect between polyols and Ca/Zn, which can delay the time of de- hydrochlorination. It was also found that the stability of dipentaerythritol is the best in all polyols, the more addition of it, the better stability of blend.