凹凸棒石/硅橡胶复合材料的热氧化降解和老化性能研究

本文采用高压均质结合对辊挤压工艺对天然凹凸棒石进行棒晶解离得到了纯度较高和比表面积较大(133.7 m²/g)的纳米解离凹凸棒石. 进一步通过机械共混法分别将天然凹凸棒石和纳米解离凹凸棒石与硅橡胶生胶复合制备了天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶材料，研究了天然凹凸棒石和纳米解离凹凸棒石对凹凸棒石/硅橡胶复合材料热氧化降解和老化性能的影响. 结果表明，天然凹凸棒石-硅橡胶和纳米解离凹凸棒石-硅橡胶在300 oC热氧老化处理0.5 h后，相比于纯硅橡胶，初始5%失重温度从385 oC提高至396∽399 oC. 系列表征结果表明，天然凹凸棒石和纳米解离凹凸棒石增强了纳米粒子与硅橡胶之间的相互作用从而抑制了纳米颗粒聚集，并且可显著提高硅橡胶侧链Si-CH₃的保存率，从而提高了该复合材料的热氧化降解和老化性能. 此外，纳米解离凹凸棒石可大大抑制纳米粒子的长大；因此老化后，纳米解离凹凸棒石-硅橡胶表现出了比硅橡胶(10.6%、7.4%和5.0%)更高的拉伸强度、断裂伸长率和撕裂强度保留率(40.6%、34.9% 和30.1%).

Thermal Oxidative Degradation and Ageing Performance of Silicone Rubber Filled with Attapulgite

The natural attapulgite (NAPT) was disaggregated by high-pressure homogenization technology com-bined with extrusion process to prepare the at-tapulgite with disaggregated rod crystal bundles (DAPT) and large specific surface area of 133.7 m²/g. NAPT and DAPT were incorporated into the silicone rubber to obtain the composite NAPT-SR and DAPT-SR by mechanical blending method, respectively. After thermal oxidative ageing at 300 oC for 0.5 h, temperature for the 5% weight loss increased greatly from 385 oC of the neat silicone rubber to 396-399 oC with addition of NAPT and DAPT. NAPT and DAPT enhanced the interaction between the filler nanoparticles and rubber matrix thus inhibited the nanoparticle agglomeration. The conservation rate of the side methyl group in NAPT-SR and DAPT-SR was greatly improved after ageing. Therefore, the ther-mal oxidative degradation and ageing performance of the silicone rubber composites was significantly reinforced. Moreover, DAPT could greatly restrain the growth of nanoparticles after ageing. Therefore, DAPT-SR showed the better retention of tensile strength (40.6%), elongation at break (34.9%) and tear strength (30.1%) compared with the corresponding mechanical properties of the neat silicone rubber (10.6%, 7.4%, and 5.0%) after ageing.