凝胶注模的凝胶反应动力学和均匀性

研究凝胶注模反应动力学与反应条件对凝胶均匀性的影响,获得合理的凝胶反应条件.研究结果表明:增加引发剂浓度、催化剂浓度和单体浓度或者升高起始反应温度,凝胶反应诱导期和反应期均缩短,但单体/交联剂比例对诱导期和反应期影响不大;增加悬浮液的固相体积分数,诱导期缩短而反应期却延长;引发剂浓度、催化剂浓度和单体浓度过高或过低,均会降低凝胶均匀性.凝胶注模单体浓度较合适质量分数的范围为10％～20％,起始反应温度应控制在20～40℃;随着单体与交联剂质量比的降低,凝胶均匀性下降:当单体与交联剂质量比低于某一值时,凝胶均匀性急剧下降.单体与交联剂的质量比应高于20∶1.

Gelation kinetics and uniformity of gelcasting

Gelation kinetics of gelcasting and the effects of reaction conditions on homogeneousness of gels were investigated,and optimal conditions of homogeneous gel were also obtained.The results show that,as the concentrations of initiator,catalyst and monomer increase or initial reaction temperature enhances,and the induction period and reaction period of gelation are shortened.However,the m(AM)/m(MBAM) ratio has little effect on the gelation.Induction period is shortened while reaction period is prolonged with increasing the solids loading of suspensions.When the concentrations of initiator,catalyst or monomer are too high or too low,the uniformity of gels will decrease.For gelcasting,the optimal monomer concentration lies between 10% and 20%(mass fraction);initial reaction temperature should be controlled between 20 ℃ and 40 ℃.As the m(AM)/m(MBAM) ratio decreases,gels become less homogeneous and even inhomogeneous.Therefore,the ratio should be larger than 20:1.