MMA/BA种子半连续乳液聚合成核过程及机理研究

引入一种不溶于水的染色剂(BL-S)作示踪剂,研究甲基丙烯酸甲酯(MMA)/丙烯酸丁酯(BA)种子半连续乳液聚合中各变量对成核过程及成核机理的影响,运用最终乳胶粒中染色剂的含量(Pdye)、最终乳胶粒子数(Npc)、胶束成核和均相成核所形成的粒子数目(Nm和Nh)等参数对聚合过程中的成核情况进行定量分析.结果发现,当引发剂浓度I]增大时,Pdye、Nh、Nm和Nh/Npc均随之增大,同时Nm/Npc相应地减小,且Nm/Npc=-0.0262I]+0.8833,表明均相成核随I]的增大而增加,但胶束成核的比例减小.乳化剂浓度E]在不同范围内对成核机理的影响不同,在E]=0.7216×10-2mol.L-1时,体系中胶束成核和均相成核比例相等,各为50%;当E]>0.7216×10-2mol.L-1时,随E]增大,成核时间t1,2逐渐缩短,Nm/Npc增加,Nh/Npc减小,胶束成核所占比例大于均相成核,胶束成核逐渐上升为主要成核方式;反之当E]<0.7216×10-2mol.L-1时,体系中胶束成核所占比例小于均相成核,均相成核为主要成核方式.当MMA的摩尔分率fMMA由0增至0.6时,Nm/Npc从80.93%下降至50%,体系中以胶束成核为主,均相成核为辅;当fMMA由0.6增至1时,Nm/Npc已降至40%,而Nh/Npc增至60%,体系中已转变成均相成核为主,胶束成核为辅.在常规和种子半连续乳液聚合中,t1,2分别为12min和6min,而Pdye变化较小,表明聚合方式只影响粒子的形成过程和成核时间的长短,对成核方式影响甚微.

NUCLEATION PROCESS AND NUCLEATION MECHANISM OF MMA/BA SEEDED SEMI-CONTINUOUS EMULSION POLYMERIZATION

A water-insoluble dye(BL-S)was used as a probe to study the influence of some factors on the process of nucleation and nucleation mechanism in seeded semi-continuous emulsion polymerization.Some parameters were analysed for quantitative study on nucleation mechanisms,the parameters include the amount of dye incorporated into the resultant latex particles(P_dye),number of the resultant latex particles(Nc_p)and the different numbers of particles which are formed by micellar nucleation(N_m)and homogeneous nucl...