Fabrication and properties of thermal insulating glass fiber reinforced composites from low temperature curable polyphosphate inorganic polymers

Glass fiber reinforced polymetalphosphate matrix composites prepared by a simple process displayed excellent thermal insulating and mechanical properties. Low-viscous Al3Cr(H2PO4)x=9,12 binders were prepared by dissolving Al(OH)3 and Cr(OH)3 or CrO3 in 85% phosphoric acid, and mixed with Al2O3 and Cr2O3 fillers. The glass fiber pre-pregs impregnated by the binder solution were laid-up and cured at 150–200 °C for 12 h under pressure, which are similar conditions to those used for carbon fiber/phenolic resin matrix composites. The composites cured using the hot-press or autoclave showed outstanding hygroscopic resistance even after standing in air for 30 days, due to the chemical stability of the cured network. Hot-press cured composites with higher density exhibited maximum flexural strengths of 155 MPa and thermal conductivity in the range 1.12–3.45 W/mK, while the porous autoclave cured composites displayed 60–77 MPa and 0.4–0.6 W/mK, respectively.