Textile waste-reinforced cotton-silica aerogel composites for moisture regulation and thermal/acoustic barrier

Silica aerogel composites reinforced with reclaimed cotton fibers obtained from textile industry wastes are here presented. These fibers were obtained from fabric leftovers of textile clothing industry, using only mechanical processes for reverting wasted fabric scraps to elementary fibers. The syntheses were carried out following environmentally friendly solutions. The post-gelation silylation/washing steps were performed applying ethyl acetate, recognized as a non-hazardous solvent. The tetraethyl orthosilicate-based aerogel composites were developed with a co-precursor having a non-hydrolysable bulky branch, isobutyltriethoxysilane, aiming to reduce brittleness and increase hydrophobicity. The aerogel matrix composition used here, reinforcement conception and modification solvent are being presented for the first time in the literature. The composites, manufactured in small cylindrical-shape (diameter ~3 cm) and disk-shape (diameter ~9 cm and ~14 cm) were silylated with hexamethyldisilazane and ambient pressure dried. Thermal conductivities were assessed by non-stationary and steady-state methods, the later yielding values 25–37% lower, achieving a value as low as 21 ± 3 mW m–1 K–1. The composites exhibit a high degree of flexibility conferred by the embedded cotton fibers, that imparted as well good acoustic insulation, since at frequencies near 1300 Hz, the sound absorption coefficient is 0.8. Cotton fibers are well known by their moisture buffering. By taking advantage of that water adsorption/desorption, the thermal regulation ability of the aerogels is studied here as a novel application for these materials. At 85% of relative humidity, silica aerogel composites with ~15 wt% of cotton fibers adsorbed 2.6 wt% of moisture and the process reversibility was confirmed. Silica aerogel composites reinforced with textile waste cotton fibers and processed with ethyl acetate, able to perform moisture buffering while acting as thermal and acoustic barrier.