Preparation of poly(aryl ether ketone ketone)–silica composite aerogel for thermal insulation application
In this study, poly(aryl ether ketone ketone) (PEKK) with trimethoxysilane pendant groups was prepared first and then chemically cross-linked PEKK–silica composite wet gel was formed through the hydrolysis and condensation reactions of the trimethoxysilane pendant groups at room temperature. 29Si solid-state nuclear magnetic resonance indicated that 70.5 % of the methoxy groups on silicon participated in the condensation reaction. The formed PEKK–silica composite wet gel was dried by freeze-drying from tert-butanol to obtain PEKK–silica composite aerogel, which consisted of polymer fibers tangled together. By adjusting the concentration of PEKK with trimethoxysilane pendant groups in solution, PEKK–silica composite aerogels with different densities (ranging from 0.17 to 0.40 g/cm3) were obtained. The resulting aerogels had small average pore diameters (ranging from 25.0 to 59.4 nm), high surface areas (ranging from 299 to 354 m2/g), low thermal conductivities (ranging from 0.024 to 0.035 W/m K at room temperature) and good mechanical property. Although PEKK lost crystallization ability after incorporating trimethoxysilane pendant groups, the cross-linked PEKK still had a storage modulus as high as 1026 MPa at 300 °C. So, even after being heated at 250 °C for 30 min in air, the pore structure of PEKK–silica composite aerogel was still intact.