Abstract
This work aims to explore how ZnO nanoparticles enhance the mechanical, photoaging, and self cleaning properties of water borne acrylic coating. Micro/nano ZnO particles (at 2 wt.% of total solid resin) were dispersed into the acrylic polymer matrices using ultrasonication to understand the effect of the size of the coating properties. The effect of ZnO particles on the properties of composite coatings (25 µm of thick) have been evaluated through various tests, such as abrasion measurement, ultraviolet/condensation (UV/CON) weathering aging, and methylene blue self cleaning. Experimental data indicated that the incorporation of ZnO particles enhanced both abrasion resistance and methylene blue removal efficiency of the water borne acrylic coatings, with nano ZnO particles being the best. However, the weathering degradation of nanocomposite coatings was more severe as compared to the coating with micro ZnO (at the same ZnO content).
Highlights
Water-borne acrylic paints are widely used to protect and decorate architectural constructions, since they have many advantages, for instance, a low percentage of volatile organic compounds, easy operation, cost-saving, good weathering resistance [1,2,3]
The morphology of the coatings with or without the presence of ZnO particles is presented in Figure 2, while the morphology of the micro-ZnO and nano-ZnO and their respective particle size distribution histogram are shown in Figure 3, which confirms the nano-ZnO particles had the particle size of ≤100 nm, but the micro-ZnO had a particle size in the range of 100–300 nm
In the case of nano-ZnO, the coating shows no sign of nanoparticle agglomeration, leading to the dense structure of the nanocomposite coating, whereas some agglomeration of microparticles is observed when micro-ZnO is added to the coating matrix
Summary
Water-borne acrylic paints are widely used to protect and decorate architectural constructions, since they have many advantages, for instance, a low percentage of volatile organic compounds, easy operation, cost-saving, good weathering resistance [1,2,3]. The drawback of this kind of paint is that it is prone to mold growth and dirt clinging. To address this problem, the manufacturers usually add some additives to paint formulations, such as RocimaTM 363, RocimaTM 623, etc. Similar to other semiconductor oxides, like TiO2, ZnO could exhibit photocatalytic activity when used in the coating. Most published works only focused on the micro-sized ZnO particles, with a very limited photocatalytic behavior in the coating system. In the case of the nanocomposite coating, their antimicrobial activity and self-cleaning ability could be achieved, with nano-ZnO being the most promising and effective photocatalyst [18,19,20,21]. The e−/h+ pairs move to the surface of the particles, where they can recombine to each other or react with oxygen and water to form the OH radicals
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