化学交联聚氯乙烯树脂的合成和结构

研究了氯乙烯/交联单体悬浮共聚时,交联单体种类、浓度和聚合温度对化学交联聚氯乙烯树脂结构的影响.对于氯乙烯/邻苯二甲酸二烯丙基酯(VC/DAP)悬浮共聚体系,凝胶含量和凝胶交联密度随DAP起始浓度的增加而增大;DAP浓度相同时,凝胶含量和凝胶交联密度随聚合温度上升而下降;当凝胶含量较高时,分子链物理缠结对凝胶交联密度有较大贡献,凝胶交联密度随凝胶含量增加而快速上升.在相同交联单体浓度下,氯乙烯/马来酸二烯丙基酯(VC/DAM)共聚物的凝胶含量最大,VC/DAP共聚物次之,氯乙烯/乙二醇二甲基丙烯酸酯(VC/EGDMA)共聚物最小,这是由于DAM单体的竞聚率小于1,且含有马来酸双键,EGDMA单体的竞聚率远大于1.

Synthesis and Structure of Chemical Crosslinked Poly(vinyl chloride) Resin

Chemical crosslinked PVC resin was synthesized by VC/crosslinking monomer copolymerization in suspension process. Effects of crosslinking monomer structure, initial concentration of crosslinking monomer and polymerization temperature on the structure of PVC resin were investigated. It showed that the gel fraction and crosslinking density of gel increased as the concentration of diallyl phthalate(DAP) increased and decreased with the increasing of polymerization temperature. Physical entanglements had great contribution to the crosslinking density of gel. The crosslinking density increased rapidly with the increasing of gel fraction when the gel fraction was high. Since diallyl maleate had three double bonds and close reactivity ratio to VC, it had a higher crosslinking efficiency than DAP. Ethylene glycol dimethacrylate(EGDMA) was used up at the early stage of VC/EGDMA copolymerization due to its higher reactivity compared with VC, so its crosslinking efficiency was much lower than that of DAP and DAM. [WT5HZ]