Abstract: In order to solve the problems of low carbon residue rate, weak carbon layer strength and smoldering of phenolic foam, this article uses silica sol as raw material, glycerin as dispersant, and potassium hydroxide as curing agent to prepare potassium polysilicate based fire-retardant coating, which is used for flame-retardant modification of phenolic foam to improve the flame retardancy, fire safety and thermal insulation performance. Scanning electron microscope, limiting oxygen index, vertical combustion tester, cone calorimeter, butane spray gun and thermal infrared imager were used to study the microstructure, flame retardancy, combustion behavior and thermal insulation performance of phenolic foam before and after the modification of potassium polysilicate based fire-retardant coating. The results show that 50 to 100 μm thick protective layer is formed on the surface of phenolic foam after the modification of potassium polysilicate based fireproof coating, which significantly improves the flame retardancy, fire safety and thermal insulation performance of phenolic foam. After the modification, the limiting oxygen index of phenolic foam is increased to more than 60.0% with a V-0 level in the vertical combustion test. The peak of heatrelease rate and total heat release decreased by 76.2% and 97.3%, respectively, and the residual carbon content increased from 0.3% of almost complete combustion to 75.0%. Moreover, the dense ceramic carbon layer formed by potassium polysilicate based fire-retardant coating can effectively block the spread of flame and heat, thereby reduce the unexposed surface temperature of phenolic foam.

Key words: phenolic foam, potassium polysilicate based fire-retardant coating, flame retardancy, combustion behavior, thermal insulation performance