环氧化改性杜仲胶与合成反式-1,4-聚异戊二烯的性能对比

基于天然杜仲胶(EUG)与人工合成反式-1,4-聚异戊二烯(TPI)微观链结构和化学组成的差异,分别采用乳液工艺和溶液工艺对二者进行了环氧化改性。采用差示扫描量热、偏光显微镜(POM)、拉力试验、扫描电子显微镜和动态力学分析对比研究了环氧度对环氧化杜仲胶(EEUG)和环氧化合成反式-1,4-聚异戊二烯(ETPI)的结晶行为、拉伸性能、动态力学性能的影响。结果显示,随着环氧度的增加,EEUG和ETPI结晶度均降低,球晶尺寸减小,EEUG在环氧度超过摩尔分数20.6%后聚集态结构由结晶转变为无定型;ETPI在环氧度超过摩尔分数13.8%后DSC曲线上没有出现熔融峰和结晶峰,但POM下仍可观察到少量小球晶。环氧基团的不均匀分布导致了ETPI的局部结晶。拉伸性能显示随着环氧度增加,EEUG硫化胶拉伸强度降低,断裂伸长率明显增加,在环氧度摩尔分数大于20.6%后实现了材料由刚而韧的塑料向软而韧的弹性体的转变。ETPI硫化胶拉伸强度和断裂伸长率均低于TPI硫化胶。动态力学性能证实EUG的环氧化改性导致其聚集态结构的转变,且这种转变与环氧度之间有明确的对应关系。ETPI力学行为的改变与环氧度之间没有明确的对应关系。EEUG-20.6和ETPI-13.8的硫化胶显示出最大的0℃时tanδ值和最小的60℃时tanδ值,说明通过控制环氧度来控制材料的聚集态结构,可同时改善材料的抗湿滑性能和低滚动阻力。

Comparison on the Properties of Epoxidized Eucommia Ulmoides Gum and Epoxidized Synthetic Trans-1,4-Polyisoprene

Emulsion and solution process were chosen separately to epoxidize eucommia ulmoides gum (EUG) and synthetic trans-1,4-polyisoprene (TPI) based on their different chain micro-structure.The effects of epoxy content on crystallization behavior,tensile properties and dynamic mechanical properties of epoxidized EUG(EEUG) and epoxidized TPI (ETPI) were comparatively studied by DSC,POM,tensile testing machine and DMA.The results indicate that both degree of crystallinity and crystal dimension of EEUG and ETPI decrease with epoxy content increasing.For EEUG,both DSC and POM results show that the aggregation structure transform from crystal to amorphous when the epoxy content exceeds 20.6％;while for ETPI,when the epoxy content is more than 13.8％,there is no melting peak or crystallization peak in DSC curves,while a few small sphero-crystal is observed in POM pictures.This suggest that epoxidation reaction of EUG system occurs homogeneously while the TPI system is not.The nonuniform distribution of epoxy group in ETPI leads to local crystallization.Tensile properties show that tensile strength of EEUG vulcanizates decreases with epoxy increasing,while elongation at break increases significantly.EEUG changes from rigid and tough plastics into soft and tough elastomer when the epoxy content exceeds molar fraction 20.6％.By comparison,both tensile strength and elongation at break of ETPI vulcanizates are lower than that of TPI.Dynamic mechanical properties of EEUG vulcanizates confirm its transformation of aggregation structure,and there is a clear correspondence between the dynamic mechanical behavior and epoxy content.The dynamic mechanical behavior of ETPI also change with epoxy content increasing,while the corresponding relationship between dynamic mechanical behavior and epoxy content is not as clear as EEUG system.EEUG-20.6 and ETPI-13.8 vulcanizates show the maximum tan δ value at 0 ℃ and the minimum tanδ value at 60 ℃,indicating a combined improvement of wet skid resistance and rolling resistance can be achieved by controlling epoxy content.