8. Water-Based Acrylic polymer/TiO₂ Coatings: Influence of the Size of TiO₂ Particles (Micro- and Nano-) on Mechanical Characteristics and Weathering Resistance

This work aims to clarify the difference between the influence of TiO₂ particles at micrometer and nanometer sizes on the mechanical properties and weathering durability of water-based acrylic coatings. Micro-R-TiO₂ and nano R-TiO₂ particles with 2 wt% content were dispersed in the emulsion acrylic polymer by ultrasonic vibration to prepare coatings. The coatings without TiO₂ particles, with 2 wt% micro R-TiO₂ and with 2 wt% nano R-TiO₂ were tested for abrasion resistance, weathering aging in UV/CON accelerated weathering chamber. Weathering aging was assessed by IR quantitative analysis, as well as the weight loss of the coating. The results showed that the micro R-TiO₂ with the 2 wt% content simultaneously enhanced the abrasion resistance and weathering durability of water-based acrylic coatings but not as effectively as nano R-TiO₂. The incorporation of 2 wt% micro-R-TiO₂ slightly increased the abrasion resistance of coating from 78.4 to 98.9 lite/mil (26% increase) while with addition of nano-R-TiO₂ at the same content, the abrasion resistance was significantly improved from 78.4 to 129.3 lite/mil (65% increase). After 48 aging cycles, the alkane CH groups and weight of the coatings without R-TiO₂ particles, containing 2 wt% micro-R-TiO₂, containing nano-R-TiO₂ lost 34.2% and 17.4%; 23.8% and 13%; 13.7% and 13%, respectively.