未填充天然橡胶/反式丁戊橡胶共混胶的耐疲劳性能及疲劳破坏机理

Flexing Fatigue Resistance and Fatigue Failure Mechanism of Unfilled Natural Rubber/Trans 1,4-Poly(Butadiene-co-Isoprene)Rubber Blends

研究了共混比对天然橡胶(NR)/反式-1,4-丁戊橡胶(TBIR)共混硫化胶的力学性能和耐疲劳性能的影响,以及共混胶的屈挠疲劳断裂机理。结果表明,随着共混胶中TBIR含量的增加,共混胶的拉伸强度先增加后降低,撕裂强度逐渐下降,而断裂伸长率和硬度变化不大。随着共混胶中TBIR含量的增加,共混胶的耐屈挠疲劳性能先升高后降低。当NR/TBIR共混比为50/50时,共混胶的耐屈挠疲劳性能最好。TBIR的结晶性是影响共混硫化胶耐疲劳性能的重要因素。当TBIR的含量低于50%时,硫化胶内部的微晶结构随着TBIR用量增大而增加,有利于增强橡胶的耐疲劳性能;但当TBIR的含量超过50%时,共混胶中微晶区的密度过大,无规分子链较少,对屈挠过程的能量耗散作用减弱,疲劳裂纹增长加快,因而硫化胶的耐疲劳性能反而下降。

Blending ratio of natural rubber(NR)/trans 1,4-poly(butadiene-co-isoprene)rubber(TBIR)blends on the mechanical properties and flexing fatigue resistance was investigated.The fatigue failure mechanism was revealed.The results show that with the increased addition of TBIR,the tensile strength of the blends initially increases and then decreases,and the tear strength decreases,but the elongation at break and the hardness change little.The flexing fatigue resistance of the blends initially increases and then decreases with the increased addition of TBIR.When the blending ratio of TBIR/NR is 50/50,the blends exhibit the superior flexing fatigue resistance.The crystallization of TBIR is a key factor to influence the fatigue resistance of the blends.When the TBIR content is less than 50%,the concentration of the micro-crystal in the blends increases with the increased addition of TBIR,which is beneficial to improve the fatigue resistance.However,when the TBIR content is more than 50%,more microcrystalline structure of TBIR and less random molecular chains of NR exist in the blends than ever,resulting in less energy dissipation and faster crack growth.Therefore,the blends show worse flexing fatigue resistance with excess incorporation of TBIR.