疏水性聚酰亚胺增强SiO_2气凝胶复合材料的制备与表征

Preparation and characterization of hydrophobic polyimide reinforced SiO_2 aerogel composites

采用化学交联、溶胶-凝胶和表面改性的方法,制得疏水性聚酰亚胺(PI)增强SiO_2气凝胶复合材料。以均苯四甲酸二酐(PMDA)和4’,4’-二氨基二苯醚(ODA)为聚合单体,3-氨丙基-三己氧基硅烷(APTES)为封端剂,合成APTES封端的聚酰亚胺,与正硅酸乙酯(TEOS)混合形成前驱体。采用酸碱两步催化凝胶、湿凝胶依次进行表面疏水改性、溶液置换及CO2超临界干燥,得到聚酰亚胺增强SiO_2气凝胶复合材料样品。利用FTIR、SEM、比表面积测试仪、万能材料试验机、接触角分析仪等表征样品的化学组成、微观形貌、孔结构、力学性能及疏水性能等。结果表明:PI质量分数为6wt%的样品密度为0.124g/cm^3,比表面积为724m^2/g,平均孔径尺寸为14nm,接触角为134°,抗压强度为0.295 MPa。20wt%含量的PI增强SiO_2气凝胶样品抗压强度为0.556 MPa。

The hydrophobic polyimide（PI）reinforced silica aerogel composite was prepared by the methods of chemical cross-linking,sol-gel and surface modification.The 3-aminopropyltriethoxysilane（APTES）end capped polyimide synthesized from pyromelliticdianhydride（PMDA）,4,4＇-oxydianiline（ODA）as the polymer monomers and APTES as the blocking agent,was mixed with tetraethoxysilane（TEOS）to form the precursor.The PI reinforced SiO2 aerogel composite samples were obtained via a technological process of acid/base two-step catalytic,surface hydrophobic modification,solvent exchange and carbon dioxide supercritical fluid drying.The chemical composition,micro-morphology,porous structure,mechanical and hydrophobic properties were studied by the FTIR,SEM,specific surface analyzer,universal testing machine and contact angle analyzer.The results show that the density of PI reinforced SiO2 aerogel composite with 6 wt% PI mass fraction is 0.124 g/cm^3,the specific surface area is 724 m^2/g,the average pore size is 14 nm,the water contact angle is 134°and the compressive strength is 0.295 MPa.When the PI mass fraction is up to 20 wt%,the compressive strength of the sample is 0.556 MPa.