Why Polyurethane Sandwich Panel Has Excellent Fire Resistance?

The fire rating of polyurethane sandwich panel has reached the B1 level of Chinese standard, and the fire performance is excellent. Why? The reasons are as follows:
(1) The thermal conductivity of polyurethane is relatively low. When the density of rigid polyurethane is 35-40kg per cubic meter, the thermal conductivity of polyurethane is only 0.018-0.024 / (m.k), which is the lowest among the currently developed thermal insulation materials, only half of EPS. In addition, polyurethane also has good waterproof and moisture-proof properties. Polyurethane is a hydrophobic material with a closed cell rate of more than 90%. Therefore, polyurethane will not increase the thermal conductivity due to water absorption, and the wall will not seep;
(2) Polyurethane is a self extinguishing material, which is not easy to burn after adding flame retardant. Polyurethane will decompose only at high temperature, and the softening point is higher than 250 ℃;
(3) when polyurethane is burned, it will generate carbon and accumulate on its foam surface, which helps to isolate oxygen from bottom foam and prevent the spread of fire. Moreover, polyurethane will not produce harmful gas at high temperature, which is harmless to human body;
(4) Because polyurethane has excellent fire resistance, it can reduce the wall thickness and increase the indoor usable area;
(5) Polyurethane has relatively stable porosity and structure, not easy to crack, strong safety, longer service life than other thermal insulation materials, and relatively high comprehensive cost performance.