苯乙烯无皂乳液聚合粒子增长及分布的演变机理

EVOLUTION MECHANISM OF LATEX PARTICLE SIZE AND ITS DISTRIBUTION IN EMULSIFIER-FREE EMULSION POLYMERIZATION OF St/Cops-Ⅰ

在少量带亲水性离子基团的共聚单体烯丙基甘油醚磺酸钠(Cops-Ⅰ)存在下,对苯乙烯(S t)无皂乳液聚合中乳胶粒子的增长过程进行了在线跟踪测定,探讨了粒径及粒径分布随时间的变化及其与转化率之间的相互关系。根据对实验数据的分析,提出了该聚合体系中乳胶粒子的增长机理。发现在聚合过程中,聚合前期主要以粒子间的聚并来实现粒子的增长,增长速率快,粒径分布窄;聚合后期则主要以吸收水相单体及引发乳胶粒内部单体进行聚合反应为粒子增长的主要方式,增长速率慢,粒径分布变宽。

The particle size and its distribution were measured on-line during the process of emulsifier-free emulsion polymerization of Styrene in the presence of small amount of Cops- I comonomer. The variation of particle size and its distribution along with the reaction time and the monomer conversion were also investigated. Based on the theoretical and experimental analyses, the growth mechanism of latex particle was proposed. It is found that in the earlier stage, the particle size increases rapidly through aggregation between the small basic particles, as a result, the particle size distribution is narrow. In the later stage, the increase in the particle size can be mainly attributed to the polymerization of monomers, while its distribution becomes broad. Nucleation process was found keeping on until later during the whole polymerization.