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.