The principle of steel structure fire protection is to use adiabatic or endothermic material to block the flame and directly burn the steel structure to reduce the speed of heat transfer to the steel and delay the temperature rise and strength reduction of the steel structure. According to the "steel structure fire-retardant coating"(GB14907-2002), steel structure fire-retardant coating is defined as applied to the building and the construction of the steel structure, can form a fire-resistant insulation layer to enhance the fire resistance of steel coatings. At present, the main domestic and foreign steel structure fire retardant coating resin, catalyst, carbon agent, blowing agent and other components.
1. Matrix resin
The matrix resin and other components compatibility, both to ensure that the coating has a variety of functions under normal conditions, but also flame retardant or high temperature flame retardant properties and excellent expansion foam performance. Normally, acrylic resin fire retardant paint carbonization layer of high quality, it is usually used as the main film-forming acrylic resin, and its modification, in order to improve the overall effect of paint.
The catalyst is a substance that can decompose phosphoric acid under certain conditions. The decomposed acid dehydrates the polyhydric alcohol so that it forms a non-flammable carbonized layer with a three-dimensional spatial structure. Usually, melamine phosphate is more water-soluble than polyphosphates and has the dual effect of catalysis and foaming. At present, melamine phosphate is the main catalyst.
3. Carbon agent
Carbon-forming agent is the material basis of the foam carbonized layer that forms a non-flammable three-dimensional structure of the coating at high temperatures, and acts as a framework for the foam carbonized layer. The carbonization agent should be matched with the catalyst in the decomposition temperature. When using polyamidoamine as a catalyst, high thermal stability high carbon polyols such as pentaerythritol, dipentinol ultra-thin fire retardant coating Guangdong Daya Bay Nuclear Power Plant bare plant roof has reached more than 10 years, can still be used normally. But the disadvantage is the construction of the smell, the coating easy to aging, starch and so on. The use of starch as a carbon agent, the coating water resistance is not easy to solve, and because of its price, dipentaerythritol seldom used in the country, the current domestic widespread use of pentaerythritol as a carbon fire-resistant coating agent.
4. Foaming agent
Intumescent fire-retardant coating only in the role of a blowing agent, in the high temperature flame can produce an expansion layer. Foaming agent in case of fire decomposition and the release of ammonia, water, carbon dioxide, hydrogen halide and other non-flammable gases, the coating reaches the softening point in the case of foam expansion, the formation of sponge-like structure.