| At present,the fire-retardant coatings for steel structures are mainly organic-type coatings,which are easy to be aged,expensive,easy to oxidize in flame retardant and accompanied by the release of a large number of toxic gases,which is inconsistent with the concept of green environmental protection in China;Most of traditional inorganic coatings are thick and non-expanding.they occupy the effective space,and the construction is very inconvenient.Therefore,there is an urgent need to develop a cheap,environmentally friendly,high-performance fire protection coating for steel structures.In this paper,based on the green and environmental inorganic materials and according to the principle of melt foaming,a new type of inorganic super thin expandable steel structure fireproof coating is developed.(collectively called a new type of coating).We optimize the basic composition of the new paint,improve the structure of the intumescent layer,improve the fire performance,and finally get the optimal formula,as follows:(1)Based on the initial formulation,the effects of cement,lime,putty and sodium silicate on the structure and properties of coatings were studied.The results show that the film forming performance and high temperature stability of the sodium silicate film forming agent are superior to other inorganic binder.The comprehensive performance of the fire retardant coating with the modulus of 1 sodium silicate and the liquid sodium silicate with modulus of 3 is the best,the dosage of solid sodium silicate is about 5%,and the content of liquid sodium silicate is about 35%,and the coating property is good at room temperature.It is stable at high temperature,and the flame retardant temperature is about 300 ?.The redispersible emulsion powder of polyvinyl acetate is used as auxiliary binder,The adhesive capacity of the coating is about 2%,and the free falling body of 0.8 meters can reach 12 times when the bonding ability is tested.(2)The effects of fillers such as silica,alumina,magnesium oxide and calcium carbonate on the comprehensive properties and structure of coatings were studied.The results showed that the structure of magnesium oxide filler expansion layer was the best,with the best dosage of 10%,the best fireproof performance and the flame retardant temperature was about 288 ?.The effects of three kinds of foaming agents,magnesium hydroxide,aluminum hydroxide and magnesium carbonate,on the comprehensive properties and the fire temperature of the coatings were studied.The results showed that the composite performance and structure of the coatings were the best.The flame retardant temperature was about 270 ? when the amount of aluminum hydroxide was 30%.(3)Based on the determination of the components of the new coating formulation,the influence mechanism of each component on the coating performance is studied.A single factor and orthogonal experiment were carried out to improve the composition of the ingredients and improve the structure of the expansion layer and improve the fireproof performance of the coating.Finally,the best formula was obtained: latex powder 2%,low melting point glass powder 7%,aluminum hydroxide 37%,magnesium oxide 10%,solid sodium silicate 5.4%,and liquid sodium silicate 37.6%.At this time,the flame retardancy temperature is about 240 ?.(4)A new type of coating is compared with the type coating.The results show that the fire test is 120 min,the final temperature of the new type coating is about 240 ?,the expansion layer is dense like honeycomb like inorganic structure,and its structure strength is nearly 350 times the strength of the organic expansion layer,and the amount of the release poison gas is greatly reduced when the flame retardancy is flame-retardant.There was almost no odor in the fire test,and the residual amount increased by nearly 75% after the flame retardant.By means of TG,XRD and other characterization methods,the chemical changes and the forming process of the intumescent substances during the flame-retardant process were analyzed.TG concluded that the inorganic residue of the new type coatings was greatly improved,because the inorganic filler was stable at high temperature,and the organic expansion layer was gradually reduced by oxidation at high temperature.XRD analysis showed that new silicon,magnesium and silicon aluminum minerals appeared in the formation of inorganic expansion layer,which had high thermal stability.Together with inorganic filler,the inorganic expansion layer can form more durable flame retardancy and heat insulation and enhance the fire resistance of steel structure.The new type of fire retardant coating developed in this paper exhibits excellent performance in all aspects.When fire retarded,the inorganic intumescent layer formed by inorganic materials with excellent thermal stability,such as magnesium oxide,alumina,silica-alumina minerals,and silicon-magnesium minerals,with outstanding fire resistance.This green,environmentally friendly,inexpensive and high-performance inorganic fire-retardant steel structural coating will promote the development of future coatings. |
PDF Full Text Request