聚合物改性SiO_2气凝胶的常压干燥制备及表征

摘要

Silica gels,which were prepared by copolymerization of TEOS with APTES,were modified with N3200（1,6-hexamethylene diisocyanate oligomer）.Polymer modified silica aerogels were obtained via drying of the silica gels under ambient pressure.The resulting materials were characterized by TGA,nitrogen adsorption-desorption,SEM,uniaxial compression tests,etc.It is found that with the increasing of polymer incorporated in silica aerogels,the shrinkage and the compressive strength of this material decrease,the bulk density and the elastic modulus firstly decrease and then increase slightly,the cracking limit strain and breaking limit strain during compression test increase dramatically.SEM observation indicates that the structure of polymer modified silica aerogels is porous network.The porosity decreases and then increases with the increasing of polymer incorporated in silica aerogels.The thermal conductivity for a sample with density of 434 kg·m-3 is 0.052 W·（m·K）-1.%以TEOS（四乙氧基硅烷）和APTES（3-氨丙基三乙氧基硅烷）共缩聚制备SiO2凝胶后采用N3200（1,6-环己烷二异氰酸酯低聚物）对其改性,经常压干燥制备了聚合物改性SiO2气凝胶。采用TGA、N2吸附-脱附、SEM和单轴抗压实验等测试方法对所制备的气凝胶进行了表征。结果表明：随气凝胶中聚合物含量的增加,气凝胶制备过程中的收缩减小,体积密度和弹性模量先降低后略有升高,抗压强度降低,开裂极限应变和破坏极限应变大幅度提高,柔韧性较改性前大有改善。聚合物改性气凝胶内部呈现疏松多孔的网络结构,孔隙率随聚合物含量的增加先降低后提高,体积密度为434kg.m-3时的热导率为0.052W.（m.K）-1。