| Steel with light weight, high strength, good scalability advantages, such as the construction industry has been widely applied. Extensively used in opera houses, gymnasiums, high buildings and so on. Although the steel does not have flammability, but the thermal conductivity, poor fire resistance, without fire protection refractory limit only 15 mins, well short of our architectural design requirements of fire safety regulations. The critical temperature of steel's machanical property is 540℃.When fire hazard happens, the break down of building which carrying capacity has been destroyed severely,leads to damage of personal casualty and economical loss. Therefore, to improve the fire resistance of steel, we must implement effective fire protection.At present, it is the most effective, economical, and practical to brush coatings on them directly. In this paper, the water soluble ultra-thin intumescent fireproof coatings for steel structure were prepared by acrylic emulsion, silicone modifying acrylic emulsion and amino functionalized/silicone modifying acrylic emulsion. Ammonium polyphosphate(APP), melamine(MEL) and pentaerythritol(PER) as flame retardant and synergist flame retardant system. The results showed that the fireproof time of fireproof coating were 54min,62min and 65min, respectively. The results showed that the intumescent flame retardant with the best flame-retardant property was obtained at the mass ratio of APP:MEL:PER=6:5:2.Boric acid, expandable graphite(EG)were used to modify super thin fire retardant coatings.Fireproof time of fireproof coating modify by co(boric acid)=3% andω(EG)=5% is 87min.Scanning electron microscope(SEM)indicated that the intumescent char had "honeycomb" structure.
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