密胺树脂硫磺微胶囊的制备及应用

Preparation and application of poly(melamine-formaldehyde) microcapsules filled with sulfur

针对橡胶硫化中的'喷霜'和橡胶裂纹的自修复问题,以升华硫为芯材,密胺树脂(PMF)为壳材,采用原位聚合法制备了密胺树脂硫磺微胶囊。研究了密胺树脂的缩聚pH值对微胶囊形态的影响,乳化剂浓度、芯材含量对微胶囊粒径的影响以及密胺树脂的缩聚pH值、液固相比(W/S)、甲醛和密胺的摩尔比对微胶囊包覆率的影响。结果表明:密胺树脂的缩聚pH值为4时制备的硫磺微胶囊形态较好;甲醛与密胺的摩尔比为2∶1,水相和硫磺的质量比为8∶1时包覆率较高;十二烷基磺酸钠(SDS)的用量为0.05 g时制备的微胶囊的平均粒径小,粒径分布范围窄。最后将制备的微胶囊应用到丁腈橡胶(NBR)的硫化中,测试表明:与硫磺硫化NBR相比,微胶囊硫磺延长了焦烧时间和正硫化时间,提高了NBR的物理性能,并且能抑制'喷霜'现象。

For the purpose of developing a novel vulcanizing agent and self-healing material,melamine-formaldehyde（MF）resin-walled microcapsules containing sulfur were prepared by in-situ polymerization.Such parameters as pH value,mass ratio of water to sulfur,molar ratio of formaldehyde to melamine,surfactant concentration and core content,were investigated by analyses of microcapsule morphology,particle size distribution and encapsulation efficiency.The morphology of microcapsules indicated that optimal pH value was 4.The mean diameter of microcapsules decreased with increasing surfactant concentration but changed slightly with core content.High encapsulation efficiency was achieved when mass ratio of water to sulfur was 8∶1,and the molar ratio of formaldehyde to melamine was 2∶1.In curometer test,the microcapsules coating sulfur curing system had longer scorch time and optimum curing time,and the vulcanized nitrile butadiene rubber（NBR）had better mechanical properties compared with those of sulfur vulcanized NBR.