Silica Nanoparticles Modified by Biphenyl Groups for Crack-Free Coating on Synthetic Paper

Water-based acrylic emulsions are a crucial component of water-based ink. Preventing visible cracks in emulsion coating during drying is a great challenge due to the high polarity and high surface tension of water. Herein, we propose that the cracking resistance of the coating can be enhanced through the incorporation of hydrophobic silica nanoparticles. The hydrophobic silica nanoparticles were fabricated by the modification of biphenyl groups to the surface of silica nanoparticles through postcoating using dimethoxydiphenylsilane. The presence of phenyl groups on the surface of biphenyl-modified silica nanoparticles (BPSNs) was confirmed by the Raman spectrum, Sears number, and zeta potential measurements. The formation of large cracks was significantly reduced by the incorporation of BPSN into water-based acrylic emulsion coatings. BPSN strengthens the forces of attraction between the resin particles in coatings, enabling the coating to resist the stresses caused by drying. This work provides a simple method to obtain crack-free coatings of water-based acrylic emulsion on a nonabsorbent substrate, offering a promising strategy for the printing industry to broaden the application of water-based ink.