静态热老化对NR硫化胶交联结构及力学性能的影响

研究了老化时间和环境对三种硫化体系的天然橡胶 ( NR)硫化胶的交联结构与力学性能的影响 .结果表明 ,三种 NR硫化胶的交联密度、定伸应力相近 ,多硫键含量最多的 CV体系硫化胶拉伸强度和伸长率最大 ,单硫键含量最大的 EV体系的拉伸强度和伸长率最小 ;有氧和绝氧热老化均使 NR硫化胶中多硫键减少 ,单硫键增加 .未填充的 NR硫化胶 ,其交联密度随热氧老化先增后减 .对于 N330填充的 NR硫化胶 ,有氧和绝氧热老化都使交联密度增加 ,拉伸强度和伸长率降低 ,而定伸应力和硬度增加 ,但 CV体系的性能保持率最低 ,EV体系最高

Effect of Crosslink Structure on Mechanical Properties of Natural Rubber Vulcanizate under Different Aging Conditions

The effects of crosslink strucures on the mechanical properties of the unfilled and carbon black N330 filled natural rubber (NR) vulcanizates cured with conventional (CV), semi efficient (SEV) and efficient (EV) cure systems were investigated. The three unfilled and N330 filled NR vulcanizates cured with the CV, SEV and EV systems show some apparent differences in the tensile strength and elongation at break in the order of CV>SEV>EV before aging, respectively, because of the highest level of the density of the polysulfidic crosslink in CV vulcanizates and the highest level of the monosulfidic crosslink in EV vulcanizates. Aerobic and anaerobic heat aging would lead to an increase in the 100% modulus and Shore A hardness and a decrease in the tensile strength and elongation at break of the NR vulcanizates due mainly to the changes in the total density and types of crosslinks. The NR vulcanizates cured with CV system show the lowest property retention because of its poor resistance to heat aging. Aerobic heat aging of NR vulcanizates caused a more significant change in physical mechanical properties than anaerobic heat aging because of the dominant effect of oxidative degradation during aerobic heat aging on the main chain structure and crosslink structures of the vulcanizates.