水相添加剂对热可膨胀聚合物微球颗粒结构和膨胀特性的影响

Effect of water phase additives on particle structure and expansion behavior of thermal-expandable polymer microspheres

通过戊烷发泡剂存在下的偏氯乙烯-丙烯腈-甲基丙烯酸甲酯（VDC-AN-MMA）悬浮共聚制备包覆型热可膨胀聚合物微球，考察氯化钠、柠檬酸和重铬酸钾等水相添加剂对聚合物微球颗粒结构和热膨胀特性的影响。结果表明氯化钠、柠檬酸和重铬酸钾的添加均可起到降低聚合过程中形成难膨胀聚合物细微粒子的作用，当氯化钠添加量为4%（质量分数，基于单体，下同）、柠檬酸添加量为2.5%～5.0%、重铬酸钾添加量为0.05%～0.1%时，制备的可膨胀聚合物微球具有粒径分布窄、形态规整、聚合物对发泡剂包覆效果好等特点；加热后未膨胀聚合物微粒数目少，膨胀均匀，膨胀温度区间宽。

Thermal-expandable polymer microspheres with core-shell structure were synthesized by suspension copolymerization of vinylidene chloride-acrylonitrile-methyl methacrylate （VDC-AN-MMA） in the presence of pentane as a foaming agent. The influence of water phase additives, such as sodium chloride, citric acid and potassium dichromate, on the particle structure and thermal expansion properties of polymer microspheres were investigated. The results showed that the additions of sodium chloride, citric acid and potassium dichromate could significantly reduce the number of un-expandable fine polymer particles. To be specific, when the loading of sodium chloride, citric acid and potassium dichromate was 4%, 2.5%—5.0% and 0.05%—0.1% （based on monomers）, respectively, the prepared expandable microspheres exhibited narrow particle size distributions, regular morphology and good encapsulation of foaming agent by polymer. Few particles were unexpanded and the expansion of particles was uniform after the heat treating of the microspheres.