The influence of chopped PI fibers on thermal, mechanical and sound insulation properties of methylsilsesquioxane aerogels

In this paper, PI-reinforced polymethylsiloxane aerogels composites were prepared by using methyltriethoxysilane (MTES) as precursor and polyimide fibers as reinforcement phase in the aqueous solvent system through acid-base two-step method and CO2 supercritical drying method. The effects of changes in the length and content of PI fibers on the thermal, mechanical, and sound insulation properties of the aerogel composites were systematically studied. The PI fiber is tightly bonded with the flexible aerogel substrate, showing good thermal properties. The density of the prepared samples is between 0.05 and 0.20 g/cm3, and the thermal conductivity is between 0.021 and 0.026 W/(m K). The thermal conductivity of samples decreases with the increase of fiber length and increases with the increase of PI fiber content, and the initial thermal decomposition temperature reaches 522.1 °C. During the compression test, PI-reinforced polymethylsiloxane aerogels did not crack in the 20% deformation compression process, and the rebound rate was between 44 and 46%, which was little affected by the reinforcing phase. The maximum compressive strength was 0.023 MPa, which was 1.4 times that of the polymethylsiloxane aerogel without adding reinforcing phase. The sound insulation property of PI simple with density around 52 mg/cm3 is mainly affected by fiber content and length change in low-frequency region, and the sound transmission loss of the sample with 3 mm and 2 wt% PI fibers reaches 18 dB at 500 Hz. Graphical abstract