笼型低聚倍半硅氧烷/硅橡胶复合材料的制备及性能进展

Progress in Preparation and Properties of POSS/Silicone Rubber Composite

利用笼型低聚倍半硅氧烷(POSS)对聚合物进行改性,已经成为近年来高分子材料领域的研究热点。其中,将POSS作为功能填料引入硅橡胶,制备POSS/硅橡胶复合材料,是有机硅材料改性的重点方向。与其他填料相比,POSS具有独特的有机-无机杂化结构,同时具备纳米级尺寸且粒径均一,可以在聚合物基体中达到分子水平的分散。POSS的这些优点使硅橡胶材料的性能进一步优化,可大大拓宽其应用范围。POSS所具有的类似SiO 2的笼型内核,赋予其较高的耐热性和优良的力学性能。因此,POSS的引入对硅橡胶材料的热稳定性能和力学性能的影响尤其显著。近几年,随着具有特殊官能团的新型POSS单体的出现,POSS/硅橡胶复合材料的性能得到进一步提升,在一些特殊领域获得一定应用。POSS作为阻燃填料,已经在硅橡胶绝热材料领域取得了不错的应用效果;将某些含氟的POSS单体引入硅橡胶中,能够明显降低硅橡胶材料的介电常数,可将其作为性能优良的低介电材料使用;用POSS作为填充粒子制备的POSS/硅橡胶混合基质膜,兼具有机膜与无机膜的优势,同时具有较高的热稳定性,已经在气体分离、生物醇回收等领域展现出较好的应用前景。然而,POSS由于在室温下容易结晶,导致其在聚合物基体中的分散稳定性较差,进而影响复合材料的性能。近几年,研究人员针对POSS在硅橡胶基体中的分散性能进行了大量研究。从分散机理入手,考察了制备工艺、POSS种类等对分散性能的影响;研究了POSS分散状态与复合材料性能的关系,取得了显著的成果。未来仍需要加大研究力度,明确POSS在聚合物中的分散机理,找到提高分散稳定性的方法。本文首先总结了POSS单体的合成方法以及POSS/硅橡胶复合材料的制备方法。然后综述了POSS/硅橡胶复合材料的性能研究进展,主要包括:力学性能、热稳定性能、阻燃性能、介电性能以及渗透分离性能。最后对POSS/硅橡胶复合材料的发展趋势进行了展望。未来,随着新型POSS单体的出现以及复合材料制备工艺的进步,POSS/硅橡胶复合材料的性能将获得更大的提高,其应用领域也将得到进一步拓展。

In recent years,the modification of polymers with polyhedral oligomeric silsesquioxane( POSS) has become a focus of new generation polymer materials. POSS was added into silicone rubber as functional filler to prepare POSS/silicone rubber composites,which was the key direction of modified silicone materials,and has attracted more and more attention. Compared with other filler particles,POSS has unique nano-size organic-inorganic hybrid structure,and can be dispersed in matrix at the level of individual molecule,which lead to the dramatic improvement in properties of silicone rubber materials,and greatly expand their application scope.POSS molecule has a cage-like core similar to SiO2,which gives it excellent heat resistance and mechanical properties. Therefore,POSS can significantly improve the thermal stability and mechanical properties of silicone rubber materials. In recent years,with the emergence of new POSS,the performance of POSS/silicone rubber composites was constantly optimized and their applications were expanding. As a silicon flame retardant,POSS has obtained good application in silicone rubber insulation materials. The introduction of fluorinated POSS monomer into silicone rubber can significantly reduce the dielectric constant of silicone rubber,and the composite can be used as low dielectric materials with excellent properties. PDMS mixed matrix membranes( MMMs) using POSS as filler particles have advantages of organic and inorganic membranes,and high thermal stability. It has shown good application prospects in gas separation and bio-ethanol recovery from aqueous solutions,etc.However,POSS molecules tend to crystallize at room temperature,which result in poor dispersion stability and affect the properties of composite. Large amount of studies have focused on the dispersibility of POSS in silicone rubber. According to the dispersion mechanism,the effects of process conditions and POSS type on dispersion were investigated. The relationship between dispersion and performance was studied,and significant results were obtained. In the future,more efforts should be made to clarify the dispersion mechanism of POSS in polymers and find ways to improve the dispersion stability.In this paper,the preparation methods of POSS monomer and POSS/silicone rubber composite are summarized. In addition,the progress in properties of POSS/silicone rubber composite including mechanical properties,thermal stability,flame retardancy,dielectric properties and pervaporation is reviewed. The development trend of POSS/silicone rubber composite is also prospected. In the future,with the appearance of new POSS compounds and the progress of preparation process,the properties of POSS/silicone rubber composite would achieve greater improvement,and its application field would be further expanded.