Synthesis of silica-polybutadiene hybrid aerogels: The effects of reaction conditions on physical and mechanical properties

The aim of this study was to synthesize a novel organic-inorganic hybrid aerogel using silane functionalized polybutadiene latex nanoparticles to enhance their physical and mechanical properties by varying the synthesis conditions. The effect of silica sol concentration, pH of the mixture during gelation and silane grafting degree of polymer latex on the structure, morphology and compression strength properties of the aerogels were studied. The silane-modified rubber particles were combined with Tetraethoxysilane (TEOS) as silica precursor by two step acid-base catalyzed sol-gel process followed by drying in ambient pressure condition. The monolithic hybrid aerogels with different polymer latex content (0-70 wt.%) were prepared. The aerogels containing up to 30 wt.% of polybutadiene latex showed lower densities (ranging from 0.19 to 0.24 g/cm3) and higher surface areas (from 763 to 461 m2/g) with negligible volume shrinkages after drying. Increasing in polymer latex content (> 30 wt.%) resulted in lower surface area along with a sharp decrease in the porosity as evaluated by Nitrogen adsorption/desorption. The aerogel samples with compression strength varying from 262 to 14,450 kPa were obtained. It was found that increasing the silane grafting degree of polybutadiene latex improved the compression strength properties > 3 × (from 262.4 to 853.6 kPa), without decreasing in porosity.