天然胶乳凝固工艺对其生热性能的影响

Effect of Natural Latex Coagulation Process on Its Heat Generation Performance

天然橡胶存在阻尼滞后现象,使其在循环使用过程中产生热量,加速其老化。天然胶乳不同的凝固工艺对橡胶网络结构的构建有重要影响,从而进一步影响其生热性能。文中通过核磁共振交联密度仪和管道模型理论分析对自然凝固(NR-n)、微生物凝固(NR-m)及甲酸凝固天然橡胶(NR-a)的网络结构进行分析,研究了橡胶网络结构与其生热性能的关系。结果表明,NR-n和NR-m外部温升分别为8.5℃和8.9℃,均低于NR-a的13.8℃;NR-n和NR-m内部温升分别为17.6℃和16.7℃,均低于NR-a的26.6℃。导致生热差异化的原因在于NR-n和NR-m的交联和缠结点密度均高于NR-a,硫化网络刚性增强,相同应力作用下NR-n和NR-m分子链运动趋势更小、热耗散少、生热更低。研究表明,自然凝固和微生物凝固的天然橡胶硫化网络致密性更好,导致其生热性能都明显优于甲酸凝固天然橡胶。

Natural rubber has a damping hysteresis phenomenon,which causes it to generate heat during recycling and accelerates its aging.The different coagulation processes of natural latex have important influence on the construction of rubber network structure,which further affects its thermogenesis performance.In this paper,the network structure of natural coagulation(NR-n),microbial coagulation(NR-m),and formic acid coagulated natural rubber(NR-a)was analyzed by NMR cross-link density meter and tube model theory,and explored the relationship between the rubber network structure and its thermogenesis performance.The results show that the external heat generation of NR-n and NR-m are 8.5℃and 8.9℃,respectively,which are lower than 13.8℃of NR-a.The internal heat generation of NR-n and NR-m are 17.6℃and 16.7℃,respectively,which are lower than 26.6℃of NR-a.The reason for the difference in heat generation is that the density of cross-linking and entanglement points of NR-n and NR-m are higher than those of NR-a,which results in an enhanced rigidity of the vulcanization networks.At the same stress,the movement trend of NR-n and NR-m molecular chains is smaller,the heat dissipation is less,and the thermogenesis is lower.Research shows that the natural coagulation and microbial coagulation of natural rubber vulcanization networks have the better compactness,as a result,their thermogenesis performance is significantly better than acetic acid coagulated natural rubber.