Preparation And Properties Of Exterior Wall Thermal-insulating Fluorocarbon Coatings

With the development of technology and the growing demands for energy of human society, energy shortage has become a serious obstacle to the progress of human society. According to relevant reports, building energy consumption accounts for 30% to 40% of total energy consumption. Therefore, heat-insulating and energy-saving for the building is significant.In this paper, the fluorocarbon emulsion is prepared with the monomer pre-emulsification polymerization method; the infrared radiative powder is prepared by high temperature solid-phase sintering technique. And then, a kind of thin exterior wall thermal-insulating and energy-saving composite coatings which coexists of three mechanisms of barrier, radiation and reflection is prepared using fluorocarbon emulsion and acrylic emulsion as the membrane material, respectively. Functional filler and reinforcing material are selected purposively, and properties of the coatings are evaluated.The influencing factors of the polymerization process and the emulsion properties are studied. The optimal formula of fluorocarbon emulsion as follows:Methyl methacrylate butyl acrylate:butyl acrylate hexafluoropropylene (mass ratio)= 0.75:1:0.9, the dosage of initiator is 0.01% of the monomer, emulsifier is 3%, buffer is 2% and protective colloid is 4 %. The optimal conditions of fluorocarbon emulsion as follows:in the pre-emulsion process, the dropping time of mixed monomers is half an hour and low-speed stirring for an hour at 50℃; in the polymeric phase, under nitrogen atmosphere and high-speed stirring, the dropping time of initiator and buffer is 2～3 h, the dropping time of the protective colloid is 1 h, polymerization continues for 3～4 h at 80℃, and then holds at 85℃for 0.5～1h. The results of FT-IR show that the fluorocarbon emulsion is synthesized. The SEM graphs of emulsion film reveal that surface of emulsion membrane is smooth and compact, its contact angle to water is close to 90°, to n-octanol is more than 80°. The rest basic properties of the coatings are qualified.The formula and polytechnic conditions of the infrared radiative powder are optimized by orthogonal test. The optimal formula as follows:Fe2O3:MnO2:CuO:CO2O3:Cordierite=7: 1.1:1.1:1:1.2; the optimal conditions as follows:the particle size is 400 mesh, the wet mixing time is 6 h, the calcining temperature is 1300℃and the calcining time is 3 h. The results of XRD pattern show that anti-spinel CoFe2O4 is generated, the infrared radiative powder is the complex of anti-spinel CoFe2O4 and cordierite, both of which are the high infrared active substances. At 26℃, in 8～13.5 Micron band, the emission rate of the composite is more than 94%.Using the self-made fluorocarbon emulsion as the membrane material, hollow glass beads, rutile titanium dioxide and infrared radiation powder as functional filler, aluminium silicate as reinforcing material, and other fillers and additives are supplemented, a kind of fluorocarbon top-coatings is prepared, which has high reflectivity more than 82%and emissivity greater than 72%. The SEM graphs show that the film has a smooth and compact surface, the rest basic properties of the coatings are good.Using acrylic emulsion as membrane material, hollow glass beads as a functional filler, aluminium silicate fibre as reinforcing filler, combine with other fillers and additives, a kind of thermal-insulating primer is prepared, of which thermal conductivity is less than 0.0600W/ (m·K). The SEM graphs show that the surface of the coatings is compact and smooth, and its internal has the characteristic of porous structure of low thermal conductivity material. And the other basic properties are fine.Combining the prepared top-coatings with primer, the low thermal conductivity, high reflectivity and high emissivity will be incarnated, and coatings containing fluoride which have perfect properties is favor to the thermal-insulating and energy-saving of exterior-wall.