| In this paper,styrene-acrylic copolymer-emulsion was prepared by the monomer pre-emulsion method,the influences of various parameters on polymerization and emulsion properties were investigated,and the polymerization condition was optimized.The aggregates,mineral wool and fillers were selected.The composite thermal insulation coating which based on mechanism of reflection and obstructing was prepared with styrene-acrylic emulsion as basic material.And the effects of each factor on heat reflectivity and thermal conductivity were analyzed with orthogonal method and single-factor method. The optimal formula was determined and the product performances were tested.The thermal conductivity (λ)was measured with pulse plane heat source method,andλwas calculated,using Origin combined with Excel.The optimum conditions for styrene-acrylic polymerizing were as follows:the time for adding monomers pre-emulsion was 1~1.5h,the temperature was held at 86℃during the polymerization,by droping pre-emulsion,initiator and buffer for 3~4h,then it was kept for 1.5~2h at 90℃.The optimal formula (based on monomer mass) of emulsion was as follows:Styrene:Butyl acrylate equaled 0.8/1～1/1,the dosages of SDS/OP-10 (1:4)complex emulsifier was 2.5%,5%PVA as a protection colloid was 2%~4%,NaHCO3(12%) as a buffer was 0.6%~0.8%.The performance specifications of the styrene-acrylic emulsion were:solid containing,49.0±0.5%,viscidity,2.546~3.472Pa·s,average shear bond strength,660KPa,the calcium ion stability and film forming ability were all good.The composite thermal insulation coating was prepared with styrene-acrylic emulsion as basic material,while expanded perlite and sepiolite as the aggregates,aluminosilicate fibers as the mineral wool,and composite titanium dioxide and hollow glass beads as the fillers.Through perpendicular experiments,the effect weight of these factors for heat reflectivity were obtained:aluminosilicate fibers> hollow glass beads >composite titanium dioxide > expanded perlite > sepiolite,while the influence on thermal conductivity were:aluminosilicate fibers> expanded perlite > hollow glass beads > sepiolite > composite titanium dioxide.Furthermore,formula of the insulation coating was optimized by single factor experiment:styrene-acrylic emulsion,50g,deionized water,45g, various additives,6g, aluminosilicate fibers,7g, expanded perlite,3g, hollow glass beads,10g, composite titanium dioxide,15g,sericite powder,18g.The average shear bond strength of the insulation coating was 660KPa,it could be raised to1026KPa after high temperature treatment,viscosity 2.123~4.059Pa·s,pencil hardness 9H,adhesion grade 1~2, its endurance to acid,alkaline and salt was strong.The reflectance of the coating at the visible band >76%,and the thermal conductivities were in the range of 0.057 to 0.072W/(m·K),TG suggested that the thermal stability of the insulation coating was good,for merely 1% loss at 300℃.SEM showed that the surface of the coating was compact,and the interior was loose,so the properties of heat insulation and water proofness were excellent.The composite thermal insulation coating could be widely applied in various fields.Thermal conductivity of insulation coating was measured by using the pulse plane heat source method,Origin7.0 was utilized for curve fitting and the expression of iterative curve fitting was inputted in Excel,then the thermal conductivity(λ),thermal diffusivity(a) and specific heat(c) could be calculated out at the same time.
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