Abstract
The present work describes for the first time the preparation of silica-based aerogel composites containing tetraethoxysilane (TEOS) and vinyltrimethoxysilane (VTMS) reinforced with Kevlar® pulp. The developed system was extensively investigated, regarding its physical, morphological, thermal and mechanical features. The obtained bulk density values were satisfactory, down to 208 kg·m−3, and very good thermal properties were achieved—namely a thermal conductivity as low as 26 mW·m−1·K−1 (Hot Disk®) and thermal stability up to 550 °C. The introduction of VTMS offers a better dispersion of the polyamide fibers, as well as a higher hydrophobicity and thermal stability of the composites. The aerogels were also able to withstand five compression-decompression cycles without significant change of their size or microstructure. A design of experiment (DOE) was performed to assess the influence of different synthesis parameters, including silica co-precursors ratio, pulp amount and the solvent/Si molar ratio on the nanocomposite properties. The data obtained from the DOE allowed us to understand the significance of each parameter, offering reliable guidelines for the adjustment of the experimental procedure in order to achieve the optimum properties of the studied aerogel composites.
Highlights
IntroductionUsually a mesoporous network, with average pore diameter between 20 and 40 nm, which provide a very high specific surface area [1]
Silica-based aerogels are lightweight amorphous materials, having very high pore volume (>90%)and usually a mesoporous network, with average pore diameter between 20 and 40 nm, which provide a very high specific surface area [1]
It is important to note that NASA has already used this technology to capture Space dust particles and in Mars exploration vehicles; research has been conducted to use these materials for thermal insulation of
Summary
Usually a mesoporous network, with average pore diameter between 20 and 40 nm, which provide a very high specific surface area [1] Another important property of silica aerogels is their very low thermal conductivity (0.015–0.025 W·m−1 ·K−1 ) [1,2], associated with non-flammable character, making them suitable materials for thermal insulation systems, even in extreme temperature environments [1]. This lightweight engineered material brings great improvement for thermal protection systems, especially in Space, but still needs to be optimized for Space conditions. The use of polymers as a strategy for Polymers 2020, 12, 1278; doi:10.3390/polym12061278 www.mdpi.com/journal/polymers
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