Research And Development Of Fly Ash-Based Inorganic High-Performance Coatings

From the beginning of 21 st century,the environmental benign,high-performance and aesthetics of architectural coatings are being pursued by people.Traditional architectural coatings are mostly organic which has good adhesion and flexibility,but their high temperature resistance and environmental friendliness are unsatisfied.Inorganic coatings have good fire resistance but poor film formation and water resistance.The unique properties of geopolymers provide ideas for solving the above problems.Fly ash is the waste produced by the boiler of thermal power plant.The production of fly ash increases rapidly with the development of thermal power generation in China,which will cause serious pollution to the environment.However,alkali activated fly ash gel material has many advantages,such as simple production process,low price and effective utilization of fly ash,thus becoming the current research hotspot.As the base material of architectural coating,alkali-activated fly ash gel material not only avoids the high pollution of organic coating,but also has the characteristics of high temperature resistance,rich resources and environmental benign of inorganic coating.In this paper,using fly ash based geopolymer as the base material,the effects of reaction temperature,water-solid ratio,silane coupling agent content,emulsion content and refractory filler ratio on the film-forming properties,water resistance,scrub resistance,adhesion,hardness,fire resistance and thermal insulation of coatings were studied.The main conclusions are as follows,(1)KH550 is alkaline after hydrolysis and has good compatibility with the system.The hydrolyzed KH550 can form Si-O-Si bond with fly ash based geopolymer,furthermore,it can also form covalent bond with organic groups in silicon-acrylic emulsion.The interior of the coating becomes dense because the resulting products with morphology of clusters fill the pores of the fly-ash based geopolymer coating.Therefore,the plasticity and hydrophobicity of the coating are improved,and the cracking resistance,water resistance and scrub resistance of the coating are strengthened.(2)The conversion efficiency of fly ash into geopolymer is improved by increasing temperature and adoping suitable water-solid ratio.In this case,fly ash is treated by alkali solution to form more active components and gel phases.(3)When the preparation temperature is 60 ℃,the water-to-solid ratio is 0.31,the content of silane coupling agent is 3.6%,and the silicone-acrylic emulsion to geopolymer ratio is 1 to 3.5,the obtained geopolymer inorganic coating has good surface properties.When the mass ratio of hollow glass beads,(magnesium hydroxide /aluminum hydroxide)and zinc borate is 2.4:1.6:2.6,and the coating thickness is 7mm,the highest temperature of the coated backplane is only 190 ℃,obviously lower than that of the controled board without adding fire resistance fillers(253 ℃),which indicates that the coating has the best propertires of fire resistance and thermal insulation.(4)The geopolymer inorganic coating is mainly composed of amorphous aluminosilicate gel.The weight loss is mainly caused by the loss of moisture and emulsion,and no obvious thermal decomposition was found,which indicates that the coating has good high temperature resistance.