湿热环境对PMMA混杂纳米复合材料性能的影响

Effects of Hygrothermal Environment on Properties of PMMA Hybrid Nanocomposites

目的研究湿热环境对聚甲基丙烯酸甲酯(PMMA)混杂纳米复合材料性能的影响。方法利用制备的水包油型杂化乳液稳定剂EMI/GO/CNTs稳定以甲基丙烯酸甲酯(MMA)为油相的水包油型Pickering乳液,用偶氮二异丁氰(AIBN)为引发剂,引发Pickering乳液进行悬浮聚合,聚合产物为PMMA混杂纳米复合材料。将PMMA混杂纳米复合材料模压成型,分别在室温及50℃下进行水浸吸湿实验。采用光学显微镜对Pickering乳液液滴形貌进行分析,通过复合材料的质量变化、动态力学分析测试、导电性测试,对复合材料的吸湿率、玻璃化转变温度及导电性变化进行分析。结果用EMI/GO/CNTs稳定的以MMA为油相的水包油型Pickering乳液具有良好的稳定性,乳液液滴的尺寸分布范围较窄,分布较均匀。复合材料的吸水量随时间增加逐渐增大,达到吸湿平衡状态后,吸湿率基本不变。不同温度下水浸复合材料的吸湿速度和平衡吸湿率不同,50℃水浸比25℃水浸的复合材料的吸湿速度快且平衡吸湿率大。湿热后复合材料的玻璃化转变温度基本不变。复合材料经湿热环境处理后电导率升高1~2个数量级。结论利用制备的杂化乳液稳定剂制备出Pickering乳液并进行悬浮聚合、模压成型,制备出PMMA复合材料。经水浸湿热处理后的复合材料,其吸湿率和电导率均有一定变化,玻璃化转变温度基本不变。

Objective To study effects of hygrothermal environment on properties of polymethyl methacrylate （PMMA） nanocomposite. Methods A methyl methacrylate （MMA） in water Pickering emulsion stabilized by EMI/GO/CNTs, hybrid emulsion stabilizers, was prepared. PMMA nanocomposites were obtained via Pickering suspension polymerization with azobisisobutyronitrile （AIBN） as initiator. PMMA nanocomposites were molded by compression molding. Moisture absorption experiments were carried out at room temperature and 50 ℃ respectively. Pickering emulsion droplets were analyzed by optical microscopy, and dynamic mechanical analysis, quality test, conductivity test were taken to value glass transition temperature, moisture absorption rate and electrical conductivity of the composites. Results The oil in water Pickering emulsion stabilized by EMI/GO/CNTs, with MMA as oil phase, showed good stability. The droplet size distribution range was narrow and the droplet distribution was homogeneous. The moisture absorption of the composite increases with time and was basically unchanged after the equilibrium state of moisture absorption was achieved. The moisture absorption rate and equilibrium moisture absorption rate of water immersion composite materials were different at different temperatures. The moisture absorption rate of the com-posite at 50 ℃ was faster than that at 25 ℃, and the rate of equilibrium moisture absorption was greater than that of 25 ℃. The glass transition temperature of composites was almost unchanged under hygrothermal conditions. The conductivity of composite after hygrothermal test was increased by 1~2 orders of magnitude than that of dry composite. Conclusion PMMA composite is prepared after the formation of stable Pickering emulsion with novel GO/CNTs hybrid emulsion stabilizer EMI/GO/CNTs as a particle stabilizer, via Pickering suspension polymerization, which is used to elaborate PMMA composites through compression molding technique. The moisture absorption rate and electrical conductivity of the composite materials after the hygrothermal test are partially changed. Glass transition temperature of the composite materials is basically unchanged.