Instant dispersion of titanium dioxide in waterborne coatings by pinning polyacrylate nanospheres

Abstract

Titanium dioxide (TiO2) with 200–400 nm diameter is an important pigment in waterborne coatings. The effective dispersion of TiO2 is a significant factor in achieving outstanding coating performance. This paper presents a novel “Instant TiO2” powder by pinning a small number of polyacrylate nanospheres (less than 5 wt%) on TiO2, which can be rapidly dispersed in water within 4 s, similar to instant coffee. The polyacrylate nanospheres copolymerized with Methyl methacrylate (MMA) and 2-Hydroxyethyl methacrylate (HEMA), are connected to the surface of TiO2 via bridge linking of silane coupling agent. This technique prevents TiO2 particles from aggregation and enables rapid dispersion of TiO2 particles in water or waterborne coating. The hydrophilic groups on HEMA facilitate the nanospheres unfolding in water to form a uniform and stable TiO2 slurry, exhibiting a significantly low viscosity (101.2 mPa·s at 200 s−1) when the concentration of TiO2 as high as 70 wt%. The “instant TiO2” denoted as TiO2-MPS-PMH shows excellent coating performance, such as impressive hiding power, and long-term storage stability under 50 °C for 28 days. Pinning polyacrylate nanospheres offers a novel approach to increase dispersion and reduce energy consumption during production in waterborne coatings by the simplified coating process. This technique also provides a potential strategy for achieving the dispersion of TiO2 in various coatings by adjusting the copolymer's components with different wettability.