聚酰亚胺纤维增强低密度柔性MTES基SiO2气凝胶的制备及表征

本文用具有环境友好性的甲基三乙氧基硅烷替代甲基三甲氧基硅烷，在水溶剂体系中，利用阳离子表面活性剂制备SiO2气凝胶基体，并以耐高温的聚酰亚胺短切纤维为增强相，制备得到了柔性疏水的SiO2气凝胶复合隔热材料。研究了聚酰亚胺短切纤维含量对复合材料热、力学性能的影响。结果表明：制备得到的SiO2气凝胶复合材料具有纤维状三维骨架结构并且气凝胶基体与增强相之间结合紧密，使得复合材料具有超疏水性，疏水角高达171°；具有良好的隔热保温性能，导热系数在0.021 W/(m·K)~0.0225 W/(m·K)之间，初始热分解高达521℃；具有较好的弹性，压缩20%形变后样品未发生增强相与基体的分离现象，并且卸压后能回弹至12%形变处。随着纤维含量的增加，复合材料里压缩强度（20%形变）逐渐增大，但是回弹率并没有较大的变化。

Preparation and Characterization of Polyimide Fiber Reinforced Low Density Flexible MTES-Based Silica Aerogel

In this paper, SiO2 aerogel composite were prepared by using polyimide chopped fiber as the reinforcing phase and SiO2 aerogel matrix prepared by replacing the methyltrimethoxysilane with environmentally friendly methyltriethoxysilane in an aqueous solvent system, via acid-base two steps method and CO2 supercritical drying. The effect of polyimide chopped fiber content on the thermal and mechanical properties of the composites was investigated. The results indicate that the prepared SiO2 aerogel composite has a fibrous three-dimensional skeleton structure and a close combination between the aerogel matrix and the reinforcing phase. It has superhydrophobicity and the hydrophobic angle is up to 171°. It has good thermal insulation properties. The thermal conductivity is between 0.021 W/(m·K) and 0.025 W/(m·K) and the initial thermal decomposition is as high as 521 °C. It has good elasticity, and the sample does not undergo separation of the reinforcing phase and the matrix after compression at 20% deformation, and can rebound to 12% deformation after pressure relief. With the fiber content increases, the compressive strength (20% deformation) in the composite increases gradually, but the rebound rate does not change much.