MMA/BA无皂乳液聚合机理研究──三阶段成粒机理

Studies on Emulsifier free Emulsion Polymerization Mechanism of MMA/BA Three stage Mechanism for Particle Formation

用Ｃｏｕｌｔｅｒ ＬＳ２３０ 激光粒径分析仪研究ＭＭＡ／ＢＡ无皂乳液共聚合中单分散粒子的成粒机理． 根据理论和实验数据分析， 其成核过程为均相成核机理． 根据粒径分布和粒子数变化情况，把无皂乳液聚合过程分为３ 个阶段： 第一阶段为成核－凝聚阶段， 体系粒子数密度迅速增加， 而粒径变化较小； 第二阶段为成核－凝聚、增长－聚并共存阶段， 当粒子数密度开始快速减少时， 标志着第一阶段结束， 第二阶段开始， 当初级粒子开始消失时， 标志着第二阶段结束； 第三阶段为增长－聚并阶段． 成核过程结束后， 粒子迅速增长， 较小粒子在增长过程中的优先聚并， 导致粒径逐渐趋向均一， 最终生成单分散性乳液．

The particle formation mechanism of monodispersed particles in MMA/BA emulsifier free emulsion polymerization was investigated with Coulter LS 230 laser particle size analyzer. The nucleation mechanism of the system is homogeneous nucleation by theoretical and experimental analyses. A three stage mechanism of the particle formation mechanism of emulsifier free emulsion polymerization is proposed. Stage 1 is a homogeneous nucleation coagulation stage. The particle number density, N , increases rapidly in this stage, but the particle size changes less. Stage 2 is a nucleation coagulation propagation aggregation stage. When N begins to decrease rapidly, it marks the end of stage 1 and beginning of stage 2. Stage 3 is a propagation aggregation stage. When the particle nucleation process ends, it marks the beginning of stage 3. Particle size increases remarkably through propagation and aggregation. N tends to level off gradually. The precedent aggregation of smaller particles during the propagation leads to produce monodispersed particles.