Preparation And Performance Study Of Environmentally Friendly Inorganic Exterior Wall Coating

Most of exterior wall coatings in our markets are emulsion paints. They appear to be inherently weak in durability related factors, such as weathering, anti-bacterial, discoloration, etc. Many efforts have been made to achieve better qualities after having intensive studies. It tends to develop wall coatings with low pollution, energy and resources saving currently and minimum volatile organic contents. Hence, the inorganic coating, an ancient material, gains the attention again due to its excellent effects of environment friendly and anti-weathering properties. In addition, the great hardness and bonding of cured inorganic coatings to the wall substrates as well as its low pollution characteristics enhance the market value of inorganic coatings.This paper discussed our development of an inorganic coating product, where silica sol was used as the main film forming agent. The binder is siliceous material instead of polymer resin in emulsion paint. Two self-developed silica sol modifiers, modifier A & B, were compared. Modifier B was used as an example to illustrate how a hard and rigid film formed in the mixture, where silica sol and calcium carbonate powders were two of main constituents. Three batches of calcium carbonate powders with different fineness were used in the experiments. It was found that the calcium silicate hydrates had formed upon the coating being cured at the open air atmosphere. These hydrates strengthen the coating film and prevent the film from cracking due to the drying of silica sol. The superior film of this inorganic coating was benefited from the formation of calcium silicate hydrates.In addition to the siliceous binder, our inorganic paint also contains extenders, pigments and some additives. Small amount of organic additives such as acrylic resin was added as film-forming aid, as well as improved consistency of the paint. The effects of individual additives on the paint product were discussed as well. Our work revealed that this paint product was optimized at PVC equal to 45 and the optimum dosages of dispersion agent and deforming agent were 1% and 0.2% respectively. Non-ionic thickener enhanced the splatter resistance of inorganic paint significantly while HEC decreased shear viscosity as well the paint cost. AMP is better than ammonia as a pH regulator in our inorganic paint product.Compared to the emulsion paints and inorganic paints on the current market, our inorganic paint product showed excellent weathering resistance, anti-bacterial function and durability. Our inorganic paint product is able to be formulated in various color hues. Benefit from low alkalinity, the color uniformity and retention of our inorganic paints is superior to the inorganic paints in current market.Furthermore, the application instruction was also provided in this work.