Preparation Of Novel Fireproofing Coatings For Steel Structures

Steel structure has been widely used in the domestic and overseas constructionindustry for its advantages such as high strength, low deadweight and wonderfulductility. Though incombustible, steel materials possess high heat conductivity andpoor fire-resisting performances. Without fire precaution measures, their fireproofinglimit is just a quarter of hour, far less than the fireproofing standard time specified bythe national construction design specifications. Effective fire precaution means shouldbe taken to strengthen the fire resistive ability of steel structure.Various fire precaution means have been utilized to protect steel structure andfire resistive coating is an ideal, effective, economical and practical one. A new typeof fire precaution coatings has been developed in 1990s, with ultra thin-filmed fireresistivity for steel structure coating which possesses excellent performances bothdecorative and fire-resisting properties. In this paper, investigation on the formulationof the new kind of coating and its flame retardant mechanism has been presented.Ultra thin-filmed fire resistive coating for steel structure consists of binders,flame-retardants and other components. Binders greatly influence the properties of theintumescent coating, ensuring its physicochemical properties under regular ambientand nonflammability and excellent intumescent effect in case of fire. The mixture ofamino resin and acrylic resin has been selected based on the comparison of thecharring layer characteristics from different resin systems. The ratio of the resins alsohas great influence on the physicochemical and fire-resisting properties of the coatingand the optimum ratio and added amount of the resins have been decided.Fire-resisting performance of the coating is determined by the fire retardantsystem. Ammonium polyphosphate(APP), AB-typed fire retardant and ammoniumdihydrogen phosphate(ADP) are selected as dehydrating agent, and melamine(MEL)as blister, pentaerythritol(PE) as carburetant. The effects of the components on theperformances of the coating have been studied and the formulation has beenoptimized. It is found that the polymerization degree of ammonium polyphosphate hasa great effect on the properties of the coating, and higher the polymerization degree is,better the physicochemical and fire-resisting properties are.The ratio of the components also has effect on the general property of the coating. Effects of the consumption of the pigment and filling on the properties of the coatinghave been investigated and the optional consumption is determined by adjusting theration of the pigment and the binders.The coating has high solid content and great surface tension. Rheological agentand flow agent are added to improve the rheologic and leveling property and storagestability and physicochemical properties are promoted simultaneously. Based on thetheory of solubility coefficient, the coefficient of the base resin system was measuredby titrimetry. Petrol 200,n-butyl alcohol and butyl lactate are selected as solventblend.By advanced apparatus and analysis methods such as thermogravimetry(TG),differential thermal analysis(DTA) and differential scanning calorimetry(DSC), thethermal properties of the fire retardants and the dried coating layer were measured andthe flame retardant mechanism was investigated. The results of TG, DTA and DSCshow that, in the whole intumescing process, APP, PE and MEL cooperate with eachother and synergism is generated.resinï¼›fire retardant systemï¼›fire retardant mechanism...