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Tuesday, 24 September 2019
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Raw materials & technologies, Applications

Novel aerogels with vinyl- and methyltrimethoxysilane in the silica structure

Wednesday, 18 May 2016

Portuguese researchers obtained flexible, monolithic and superhydrophobic silica aerogels by combining methyltrimethoxysilane (MTMS), vinyltrimethoxysilane (VTMS) and tetramethylorthosilicate (TMOS) in a one-step base-catalysed co-precursor sol-gel procedure.

The obtained aerogels show negligible particle shedding, which is a valued characteristic for aerospace applications. Source: Maksym Yemelyanov

The obtained aerogels show negligible particle shedding, which is a valued characteristic for aerospace applications. Source: Maksym Yemelyanov

Polybutylacrylate (PBA) and polystyrene (PS) were grafted and cross-linked in the gel aiming to enhance the mechanical performance. Fourier transform infrared spectroscopy, thermogravimetry analysis and scanning electron microscopy confirmed the presence of the polymers as a binding coating on the 3D silica network, primarily formed by firmly connected 3–5 μm secondary particles.

Obtained aerogels have touch feeling

When compared to the MTMS-based aerogels, the VTMS–MTMS–TMOS-derived aerogels, either reinforced or not, show a threefold increase of the bulk density (to ~150–160 kg m−3) and a consequent decrease in the surface area and average pore size; the thermal conductivity also increases to 60–70 mW m−1 K−1, a 50 % increase over the values of MTMS-derived aerogels. Although these tendencies are more marked in the polymer-reinforced materials, the change of the silica skeleton from MTMS to VTMS–MTMS–TMOS is responsible for the main differences. The VTMS–MTMS–TMOS underlying structure gives a fourfold increase in compressive strength relatively to the MTMS-derived aerogels, even when not reinforced. In addition, it retains a high elongation at break (40–50 %) and flexibility-modulus of 25 kPa for the PBA-reinforced aerogel, the more flexible aerogel, and modulus of 91 kPa for PS-reinforced aerogel, the stiffer and stronger material. The obtained aerogels have touch feeling that resembles that of expanded polystyrene foams, and also show negligible particle shedding, which is a valued characteristic for aerospace applications.

The study is published in: Journal of Materials Science, July 2016, Volume 51, Issue 14, pp 6781-6792.

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