鲜胶乳凝聚法制备粉末天然橡胶及其性能研究

采用凝聚法,以鲜胶乳为原料制备粉末天然橡胶(PNR),研究了胶乳凝聚影响因素、产品粒径分布和产品干燥条件,并测试了其性能。结果表明,胶乳的pH值为9.3~9.4,硫酸铝用量为3.70%~3.77%为宜,胶乳浓度对产品收率影响不大;隔离剂纳米二氧化硅的用量在2~3份为宜,产品粒径处于1.0~4.0 mm的比例在83%以上。与酸凝天然橡胶相比,制备的PNR的灰分含量、氮含量、挥发物含量、P o和PRI都较高,丙酮溶物含量和门尼粘度较低;PNR混炼胶的M min较小,Δt30相差不大;PNR混炼胶的M L和V M较小,t10和t90较大,硫化速率较慢;PNR硫化胶的拉伸强度、300%定伸应力和500%定伸应力较高,扯断伸长率较低。

Preparation and Properties of Powdered Natural Rubber by Coagulation from Fresh Latex

Powered natural rubber (PNR) was prepared by coagulation from fresh latex and the effects on coagulation, size particle and drying process conditions were investigated. The results showed that the optimal conditions were: pH of fresh latex was 9.3-9.4, the quantity of coagulant was 3.70%-3.77% and the dosage of isolating agent was 2-3. Concentration of fresh latex had little influence on the yield of PNR and the portion of PNR with particle size distribution of 1.0-4.0 mm was higher than 83%. Ash content, nitrogen content, Po and PRI of PNR were all higher than that of acid coagulated natural rubber, while Mooney Viscosity, impurity content and acetone soluble content were lower. The rubber compound of PNR had better flowability, lower ML, higer MH and a slower curing rate. After being vulcanized, the tensile strength and 300% stretching stress of PNR were larger than that of NR-a, while its elongation at break was smaller.