核磁共振法表征硫黄用量对天然橡胶交联密度及结构的影响

Influence of amount of sulfur on crosslinking density and structure of natural rubber characterized by nuclear magnetic resonance spectroscopy

用核磁共振(NMR)法测定了硫黄用量及硫化温度对天然橡胶(NR)硫化胶交联结构的影响,并与传统的平衡溶胀法进行了对比。结果表明,用NMR法可以测定硫化胶的总交联密度、未硫化胶的物理交联密度和由于交联反应产生的化学交联密度;NR硫化胶的总交联密度和化学交联密度随硫黄用量的增加而呈线性增加;随着硫黄用量的增加,交联密度增加,NR硫化胶的纵向弛豫时间和横向弛豫时间下降;NR硫化胶的交联密度越大,弛豫时间对温度的依赖性越小;NMR法可以清晰展示NR/硫黄/促进剂NS硫化体系的硫化过程中橡胶交联点间的相对分子质量、化学交联密度及橡胶大分子连到橡胶交联网络上的演变过程。

The influences of amount of sulfur and curing temperature on the network structure of natural rubber（NR） were characterized by nuclear magnetic resonance （NMR） spectroscopy, and the results were compared with those got from equilibrium swelling method. The results showed that total and chemical crosslinking density of the vulcanizates and physical crosslinking density of uncured NR could be measured by NMR spectroscopy. The total and chemical crosslinking density of NR vulcanizates increased linearly, spin-spin relaxation time and spin-lattlce relaxation time decreased with the increase of sulfur amount. The higher the crosslinking density, the lower the temperature dependence of the relaxation time. Crosslinking density measurement by NMR spectroscopy could more clearly demonstrate the evolution of relative molecular mass between crosslinking point, chemical crosslinking density of NR/sulfur/accelerator NS system and the process of long molecular chains joining to the network during the vulcanization process.