表面活性剂存在条件下脲醛树脂微球的合成反应过程

考察了酸性和不同表面活性剂存在条件下脲醛树脂微球的合成反应过程.中性Tween80和阳离子CTAB表面活性剂中生成的微球粒径分布窄,而阴离子表面活性剂中所得产物明显团聚,当预聚脲醛树脂粒子生成后加入中性和阳离子表面活性剂使产物微球的分散性和球形完整性明显改善.表面活性剂存在条件下产物的结晶性增强,初始反应的速率减慢,但中性和阳离子表面活性剂中初级粒子生成的诱导期延长、拉曼吸收增强、所得微球带正电荷;而阴离子条件下生成产物的相应特征正好相反.以上结果可以用表面活性剂的两亲性和电性对脲醛树脂微球的成核和生长过程的影响来解释.

Synthesis of Urea-Formaldehyde Resin Microspheres under Surfactant Conditions

The synthesis of urea-formaldehyde resin microspheres has been conducted with different surfactants under the acidic conditions.Narrow size distributions of resin microspheres are obtained in the presence of neutral surfactant Tween80 and cationic CTAB,while in that of anionic surfactant the resin product displays severe aggregation.After the prepolymer particles develop under conditions of neutral or cationic surfactant,the dispersity and spherical integrity of the microspheres improve significantly.Crystallinity of the microsphere products increases and the initial reaction rate slows in the presence of surfactant.In the case of neutral or cationic surfactant,the induction period of the prepolymer particles extends,the Raman absorption enhances,and the charge of the particles is positive,however,in the case of anion surfactant,the results are opposite to that described above.These results could be explained by the influence of surfactant amphiphilic and electrical properties on the nucleation and growth process of urea-formaldehyde resin microspheres.