交联键类型对未填充NR硫化胶动态力学性能的影响

EFFECTS OF CROSSLINK TYPES ON DYNAMIC MECHANICAL PROPERTIES OF GUM NATURAL RUBBER VULCANIZATES

分别用平衡溶胀法、平衡弹性模量 E′和应力 -应变方法对 3种硫化体系的 NR硫化胶的交联密度进行了测定和估算 ,同时借助化学探测剂方法测定了 3种硫化胶中各种交联键型浓度分布 ,并研究了交联键类型对硫化胶动态力学性能的影响。结果表明 ,用平衡弹性模量 E′估算的交联密度值最高 ,用平衡溶胀方法的估算值最低。3种 NR硫化胶具有相似的交联密度 ,但交联键型密度不同 ,多硫键含量最多的CV硫化体系具有稍低的玻璃化转变温度 Tg(- 5 7.1℃ )以及 Tg 以上区域内较低的动态损耗因子tanδ;SEV和 EV体系的 Tg 分别为 - 5 5 .6℃和 - 5 3.5℃ ,但 EV体系具有最高的动态损耗因子

The crosslink densities of three kinds of gum natural rubber vulcanizates were estimated from three methods of equilibrium swelling, storage modulus E ′and stress strain measurement, respectively. The effects of the crosslink types identified by chemical probes on the dynamic mechanical properties of gum NR vulcanizates cured with conventional(CV), semi efficient(SEV) and efficient(EV) cure systems, showing nearly the same total corsslink densities, were investigated by dynamic mechanical analyzer Reometric Scientific TM DMTA Ⅳ. Various cure systems with different concentration of polysulfidic, disulfidic and monosulfidic crosslinks gave different response to the temperature dependence of the dynamic viscoelasticity. The T g value and the dynamic hysteresis factor tan δ at the rubbery plateau region above T g of CV vulcanizate were lower than the SEV and EV vulcanizates with the most levels of disulfidic and monosulfidic crosslinks, respectively.