| Because of the excellent resistance and decorative properties,ultro-thin fire-proof coatings for steel structure has been more widely used in large buildings.But it has disadvantages such as bad adhension and crack resistance,so the fire-proof coatings was prepared with epoxy-acrylate modified hybrid emulsion as matrix,organic fibers or whiskers as modifier,modified magnesium hydroxide and aluminum hydroxide as flame retardant additives. The results shows that the synergetic effect of the individual components of the fire retardant coating is good.The foaming expansion effect is obvious,and the char layer is compact.(1) In recent years,waterborne eoxy resin with water as solvent had been growing concerned by people. Because of it,s characteristics of environmentally friendly,and were conducive to construction,wterborne eoxy resin has been the development of epoxy resin. First,non-ionic water-based epoxy emulsifier solution was prepared by PEG2000 and E-51 as composition,and then it was used as emulsifier to prepare waterborne epoxy emulsion.The preparation and impact factors of waterborne epoxy resin was researched.The infrared spectroscopy and laser particle size analysis was used to characterize the homemade emulsifier and epoxy emulsion.It shows : the nonionic emulsifier prepared at the reaction temperature of 60℃,with the PEG2000/E51 ratio of 1:1, with triethanolamine as initiator has a better emulsifying ability on epoxy resin. When the reaction temperature is 75℃,the reaction temperature was 60℃,the epoxy resin prepared by high-speed dispersion has best stability.(APS)(2) Acrylic has advantages of good cohesiveness,weatherability and film-forming properties,but disadvantages of bad adhesion and water resistance. Epoxy resin has good adhesion,chemical resistance,and mechanical Properties.So acrylic was modified by epoxy resin,which was one of the effective ways to improve the performance of acrylic.The acrylic resin was modified by homemade waterborne epoxy emulsion as modifier,methyl methacrylate(MMA)、acrylic acid( AA) 、 butyl acrylate(BA) and styrene(St) as comonomer, ammonium persulfate(APS) as initiator,SDBS and OP-10 as composite emulsifier. The result shows that the performance of epoxy-acrylate modified hybrid emulsion was better when the SDBS/OP-10 ratio was 1:1, and the soft/hard monomers ratio was 1, the amount of composite emulsifier(SDBS/OP-10) was 4.0%, the amount of initiator(APS)was 0.6%, the amount of epoxy emulsifier was 10%(All of them were compared to the total mass of mixed monomers),and the reaction tempreture was 70~80℃. The conversion rate of monomers was above 95%,and the calcium ion stability of epoxy-acrylate modified hybrid emulsion were good,the water absorption of film was less than 5.0%,and the adhesion level was 1.The modified acrylic resin has little change in stability.The adhesion,hardness,water resistance and chemical resistance of modified fire retardant coating has a obvious improvement.(3) The steel structure fire retardant coating was prepared with acrylic emulsion and epoxy modified acrylic emulsion as matrix respectively,ammonium polyphosphate/ pentaerythritol/ melamine as retardant intumescent systems,glass fiber,aramid fibers,calcium sulfate whisker as modifier,modified magnesium hydroxide and aluminum hydroxide as flame retardant additives,water as dispersion medium. Using the single-factor analysis and orthogonal design to study the influence of different matrix and different modifier on performance of fire-proof coatings.It gained the best condition as follows:the ratio of ammonium polyphosphate/ pentaerythritol/ melamine is 25:15:10vinylidene,the ratio of emoulsion dosage/ retardant intumescent systems/stuffing is 3:5:1. The mechanical strength fire retardant coating modified by organic fibers and whiskers has varying degrees of improvements. |
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