Preparation of emulsifier-free acrylate cross-linkable copolymer emulsion and application in coatings for controlling indoor humidity

Abstract

Indoor humidity has an important influence on our lives. Too high relative humidity (RH > 60 %) can cause the metal surface corrosion, electrical insulation fall, material deformation and so on. On the contrary, when the moisture content is too low (RH < 40 %), it causes skin chapping, decrease in respiratory system resistance, static electricity, etc. The humidity controlling coating is a kind of composite that controls the humidity of materials. In this study, the emulsifier-free acrylate copolymer emulsion (EF-AAC) containing ketocarbonyl and carboxyl groups was synthesized and the humidity controlling coating (EF-AAC-C) was prepared by EF-AAC, adipic dihydrazide (ADH) and porous fillers. The different proportions and the contents of KPS, NaHCO3, and the effects of polymerization time and reaction temperature on the stability of emulsion were investigated. The different ratios of fillers/emulsion and ADH/diacetone acrylamide for water resistance of coatings were also studied. Moreover, the structure of emulsifier-free acrylate copolymer was characterized by FTIR and TGA techniques. The particle morphologies were measured by transmission electron microscopy and dynamic light scattering. It showed that the distribution of emulsion particle size was narrow and uniform. The properties of humidity controlling coatings were studied with particular attention to the effects of the humidity controlling. Meanwhile, the water absorption of humidity controlling coatings was up to 260 %. The humidity controlling coatings revealed excellent properties of humidity sensitivity and humidity retention because of the composite porous structure due to fillers with emulsifier-free acrylate copolymer. The mechanism of breathing water molecules in obtained coatings was suggested and the composite could be widely used as indoor coatings for controlling humidity.