超声波对醋酸乙烯乳液(VAC)聚合的影响(英文)

Effect of Ultrasonic Wave on the Polymerization of Vinyl Acetate (VAC) Emulsion

对比了醋酸乙烯(VAC)在传统聚合中和超声波辅助聚合中的单体转化率和乳液粒径分布的差别.在VAC聚合过程中外加超声波环境,单体转化率从92.5 %提高到98.8 %,乳液粒子平均粒径从136.7nm减小到101.4nm.在超声波辅助VAC乳液聚合中,研究了引发剂浓度和反应温度对单体转化率及乳液粒径分布的影响.试验结果表明仅靠超声波产生的自由基不足以引发聚合反应,引发剂分解产生的自由基在引发聚合过程中起着重要的作用.简单介绍了超声波辅助乳液聚合的机理,超声波可以连续提供自由基,而这些自由基的作用是使死聚合物链变得有活性,导致单体具有较高的转化率.

The monomer conversion efficiency and average particle size and its distribution of vinyl acetate （VAC） polymerization by conventional and ultrasonic-assisted means individually were compared. With adding ultrasonic waves in the VAC polymerization, the monomer conversion efficiency was increased from 92.5% to 98.8%, and the average particle size of latex was reduced from 136.7nm to 101.4nm. During the process of ultrasonic-assisted polymerization of VAC system, the effects of initiator concentration and reaction temperature on the conversion efficiency and average particle size distribution were studied. The experimental results demonstrated that the radicals generated from ultrasonic energy solely were not enough to propel the polymerization perfectly and the radicals produced by decomposition of initiator play an important role in driving polymerization. Furthermore, the mechanism of ultrasonicassisted emulsion polymerization was briefly deduced. It was also found that ultrasonic waves maintained a constant supply of radicals and these radicals were able to reactivate some of the non-active polymer chains, so that it resulted in the higher conversion efficiency of the monomer.