Preparation and characterization of building insulation material based on SiO2 aerogel and its composite with expanded perlite

This article aims to complement the advantages of SiO2 aerogel and expanded perlite (EP) to prepare high-performance building insulation materials. SiO2 aerogels were prepared via acid/base two-step catalytic process followed by ambient pressure drying (APD) process. The two-step surface modification method is used to improve hydrophobicity of aerogel. And SiO2 aerogel/EP thermal insulation composites were obtained via introducing wet gel into EP. The effects of the amount of water, the amount of anhydrous alcohol and the pH value of sol on the properties of aerogels were analyzed. And the effects of vacuum degree and adsorption time on the thermal conductivity and compressive strength of SiO2/EP composite were studied. The pore size distribution and chemical structure of SiO2 aerogel were characterized by N2 adsorption-desorption test and Fourier transform infrared spectroscopy (FTIR). The micromorphology, crystal structure of SiO2 aerogel and SiO2/EP composite were characterized by scanning electron microscope, X-Ray diffraction. The results show that the thermal conductivity of SiO2 aerogel prepared with tetraethoxysilane (TEOS): methyltriethoxysilane (MTES): ethanol (EtOH):H2O = 1:0.3:14:6 (mole ratio) was as low as 0.0212 W/(m·K), the aerogel had high porosity (95.05%) and super hydrophobicity(the contact angle is 158.7°). Meanwhile, it was found that SiO2 aerogel is stably distributed in the pores of the EP and effectively reduces its thermal conductivity and water absorption. The minimum thermal conductivity of SiO2/EP composite was 0.036 W/(m·K), the minimum water absorption was 9.2% and the compressive strength was 214.35 kPa. Hence, SiO2 aerogel/EP with good performance and low cost has great potential in the field of building insulation.