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Silica aerogels are highly porous materials with exceptional thermal insulation performance. They become even more attractive if combined thermal and acoustic insulation is achieved. Silica aerogel composites reinforced with fibres are an ingenious way to surpass the fragility stemmed from the aerogel's intrinsic porosity, and textile fibres are good sound absorption materials. Reclaimed fibres are a relatively low-cost feedstock and were obtained in this work exclusively through mechanical processes from textile wastes, thus promoting the concept of circular economy, namely for cotton, polyester and wool fibres. These reclaimed fibres were used as reinforcement matrices for silica aerogel composites obtained from sol–gel transformation of tetraethyl orthosilicate and isobutyltriethoxysilane/or vinyltrimethoxysilane precursors and dried at ambient pressure after silylation. Silica aerogel composites reinforced with reclaimed cotton fibres had the best sound absorption coefficient (a peak value of 0.89), while the polyester-reinforced composite exhibited the lowest thermal conductivity (k = ~24 mW m−1 K−1, Hot Disk). The better combined results on thermal and acoustic insulation were achieved by the wool-reinforced composites. The thermal conductivity values were less than 27 mW m−1 K−1, and the sound absorption coefficient achieved a peak value of 0.85. Therefore, the aerogel composites developed here can be selected for thermal or/and acoustic barriers by choosing a suitable type of fibre. Their design and preparation protocol followed environmental-friendly and cost-effective approaches. [ABSTRACT FROM AUTHOR]

The use of natural fibers is a sustainable alternative for developing reinforced-polymer composites. It is believed that the seed flosses of common milkweed, Asclepias Syriraca, may be a promising reinforcing fiber given its uncommon hollow microstructure that is associated with both high specific properties and outstanding insulating capacities. This study presents an overview of the properties of milkweed floss and its potential use in reinforced-polymer composites. Milkweed flosses from Quebec were analyzed to determine their overall dimensions, density, porosity, coefficient of acoustic absorption, thermal conductivity, thermal resistance, and elastic modulus. In parallel, a portion of milkweed fibers was treated with acetone to modify their surface, and the properties of the treated fibers were measured and compared against the characteristics of the original fibers. Infrared spectroscopy was employed to assess differences between the chemical groups on the surface of treated and native fibers. The treatment with acetone removed fatty acids, waxes, and free sugars from the fibers’ surface. The acetone treatment did not affect the fibers’ microstructure nor their acoustic absorption capacity. The acetone-treated fibers showed greater thermal resistance and a higher thermal conductivity than native milkweed floss. The elastic modulus of milkweed decreased by nearly 49% after the acetone treatment. [ABSTRACT FROM AUTHOR]

Silica aerogels are highly porous materials with exceptional thermal insulation performance. They become even more attractive if combined thermal and acoustic insulation is achieved. Silica aerogel composites reinforced with fibres are an ingenious way to surpass the fragility stemmed from the aerogel’s intrinsic porosity, and textile fibres are good sound absorption materials. Reclaimed fibres are a relatively low-cost feedstock and were obtained in this work exclusively through mechanical processes from textile wastes, thus promoting the concept of circular economy, namely for cotton, polyester and wool fibres. These reclaimed fibres were used as reinforcement matrices for silica aerogel composites obtained from sol–gel transformation of tetraethyl orthosilicate and isobutyltriethoxysilane/or vinyltrimethoxysilane precursors and dried at ambient pressure after silylation. Silica aerogel composites reinforced with reclaimed cotton fibres had the best sound absorption coefficient (a peak value of 0.89), while the polyester-reinforced composite exhibited the lowest thermal conductivity (k = ~24 mW m−1 K−1, Hot Disk). The better combined results on thermal and acoustic insulation were achieved by the wool-reinforced composites. The thermal conductivity values were less than 27 mW m−1 K−1, and the sound absorption coefficient achieved a peak value of 0.85. Therefore, the aerogel composites developed here can be selected for thermal or/and acoustic barriers by choosing a suitable type of fibre. Their design and preparation protocol followed environmental-friendly and cost-effective approaches.