Preparation and characterization of polymer modified silica aerogels dried under ambient pressure

Silica gels, which were prepared by copolymerization of TEOS with APTES, were modified with N3200 (1,6-hexamethylene diisocyanate oligomer). Polymer modified silica aerogels were obtained via drying of the silica gels under ambient pressure. The resulting materials were characterized by TGA, nitrogen adsorption-desorption, SEM, uniaxial compression tests, etc. It is found that with the increasing of polymer incorporated in silica aerogels, the shrinkage and the compressive strength of this material decrease, the bulk density and the elastic modulus firstly decrease and then increase slightly, the cracking limit strain and breaking limit strain during compression test increase dramatically. SEM observation indicates that the structure of polymer modified silica aerogels is porous network. The porosity decreases and then increases with the increasing of polymer incorporated in silica aerogels. The thermal conductivity for a sample with density of 434 kg·m^-3 is 0.052 W·(m·K)^-1.