Study On Preparation Of Super-thin Fire Resistive Coatings For Steel Structure From Silicone Modifying Acrylate Resin

Steel structure has been widely used in the domestic and overseas construction industry for its advantages such as high strength, low deadweight and wonderful ductility. Though incombustible, steel materials possess high heat conductivity and poor fire resisting performance. In the case of fire such materials distort and lead to the collapse of building structures as long as the temperature of steel exceeds the critical temperature of 540℃.When heated, Ammonium polyphosphate(APP) of the dehydrating agent decomposes to yield acid which reacts with pentaerythritol(PER) of the carbonaceous char-forming agents to form an ester. The ester begins to dehydrate and cross-linking to char simultaneously with the evolution of gas from melamine(MEL) of blister and melting and softening of resin binder. In the end, fire-retardant coatings form an expandable multi-cellar charred protective layer with poor coefficient of thermal conductivity, which limits the heat transfer from the heat sources to the substrates. As a result, steel structure can be protected well.Super thin fireproof coatings for steel structure are composed of binder of silicone modifying acrylate resin, the fire retardant system, and main pigments and fillings. In this paper, super thin fireproof coatings for steel structure were prepared. The synthesis of binder of silicone modifying acrylate resin and the effect of fire retardant system and main pigments and fillings on the physicochemical and fire-resisting properties for super thin fireproof coatings for steel structure were investigated.Silicone modifying acrylate resin was obtained by the graft reaction of acrylate resin and silicone-oligomer.Acrylate resin was synthesized by the polymerization of methyl methacryla- te(MMA),acryl acid(AA),butyl acrylate(BA) and other homogeneous monomers with zaodiis- obutyronitrile (ABIN) as initiator, Silicone-oligomer was prepared by the hydrolysis and poly- condensation reaction of methyltriethoxysilane,phenyltriethoxysilane and dimethyldiethoxyls- ilane with hydrochloric acid as catalyst. Structures of resin synthesized were characterized by IR. By means of orthogonal experimental design, the key factors for preparation of silicone modifying acrylate resin and fire resisting properties of coatings were discussed by ratios of different kinds of silicone monomers, silicone-oligomer and acrylate resin, initiator dosages etc. In the end, the optimal formulas and processes for resin synthesized and fireproof coatings were determined.Fire resisting performance of coatings was determined by the fire retardant system. APP was selected as dehydrating agent, MEL as blister, and PER as carburetant. The effect of the different components on the performance of coatings has been studied and the formula has been optimized. The results of experiment showed that the physicochemical and fire resisting properties of coatings were the best if the optimal formula was selected.By advanced apparatus and analytical methods such as thermogravimetry(TG),and differential scanning calorimetry(DSC),the thermal properties of the fire retardants and the dried coating layer were measured and the flame retardant property was investigated. The results of TG and DSC showed that APP,PER and MEL cooperated with each other and synergism was generated in the whole intumescing process.The ratio of components had an effect on the physicochemical and fire resisting properties for fire resisting coatings. The effect of consumption of pigments and additives on the fire resisting coatings had been investigated and the optional consumption was determined by the test of fire proofing time with adjusting the ratio of pigments and additives of superfine SiO₂ powder and TiO₂.Super thin fireproof coatings for steel structure from silicone modifying acrylate resin were prepared by the optional formula and the optimal ratio of the components. The coatings prepared had excellent resisting weather and the fireproof time reached 116 minutes.