锰离子对天然橡胶老化性能的影响

研究锰离子含量对天然橡胶(NR)热氧老化、紫外老化和臭氧老化前后性能的影响,并采用核磁交联密度分析仪、DSC分析仪和傅里叶红外分析仪探究老化前后分子链结构的变化。结果表明,在老化之前,含有不同量的锰离子的天然橡胶的物理机械性能基本一致。经3种方式老化后的胶样性能均有不同程度的下降,当锰离子质量分数为0.000 30%时,天然橡胶老化后的拉伸强度、300%定伸应力、700%定伸应力下降程度最小。核磁交联密度测试表明,总交联密度(XLD)与网链分子量(Mc)有很好的对应关系,XLD随着锰离子质量分数的增加而先增大后减小,表明天然橡胶老化过程中交联反应和断裂反应存在竞争关系。示差扫描量热(DSC)测试发现,随着锰离子质量分数的增加,天然橡胶的玻璃化转变温度(Tg)先升高后降低,与核磁交联密度测试结果一致。红外分析(FTIR)发现,天然橡胶老化过程中发生了交联和断裂反应。

Effect of Manganese Ion on the Properties and Aging Mechanism of Natural Rubber

The effect of manganese ion content on the properties and molecular chain structure of natural rubber (NR) before and after thermal oxidative aging,UV aging and ozone aging were studied using magnetic crosslink density analyzer,DSC analyzer and Fourier transform infrared analyzer to explore the mechanism of aging.The results showed that the physical mechanical properties of natural rubber containing different amounts of manganese ions were basically consistent with the aging before aging.By the three ways after aging colloid properties had different degrees of decline.When the manganese ion concentration was 0.000 30％,the tensile strength,300％ tensile stress and 700％ tensile stress decreased least.Crosslink density test showed that the total crosslinking density (XLD) and net chain molecular weight (Mc) had a good relationship,XLD with the increase of manganese ion mass fraction increased first and decreased in the aging process,showing that the natural rubber crosslinking reaction and breaking reaction in competition.The results of differential scanning calorimetry (DSC) showed that the glass transition temperature (Tg) of natural rubber increased first and then decreased with the increase of Mn ion mass fraction,which was consistent with the results of nuclear magnetic cross link density test.Infrared analysis (FTIR) found that the aging process of natural rubber in the process of crosslinking and fracture.