Dual-functional SiO2 microspheres with rosin and PEG shells for stable, high-adhesion water-based inks

Water-based inks offer a sustainable alternative to solvent-based systems, yet their performance remains limited by particle sedimentation, poor dispersion, and insufficient film adhesion. In this study, multifunctional hybrid microspheres (SiO 2 -g-R-P) were synthesized by sequentially grafting rosin-derived acrylates and polyethylene glycol (PEG) onto silica particles. The rosin shell enhances compatibility with polyurethane–acrylic binders, while PEG chains provide steric stabilization and hydrophilicity. When incorporated at 1.5 wt% into water-based inks, the modified microspheres markedly improved dispersion stability (ζ potential = −51.6 mV), suppressed sedimentation for over 60 days, and enhanced low-shear viscosity by forming a weak reversible 3D particle network, with the formation of this network demonstrated via oscillatory rheometry (average G″ = 0.35 Pa, average G′ = 7.82 Pa). The resulting inks achieved high-resolution image transfer and strong substrate adhesion (ASTM D3359 rating 2B to 5B) on both paper and steel substrates, outperforming the unmodified formulation. These improvements stem from the synergistic effects of hydrogen bonding, steric hindrance, and particle–matrix interactions at the ink–film interface. This surface-engineering strategy provides a scalable and environmentally friendly approach for developing high-performance inks with enhanced print fidelity, mechanical durability, and colloidal stability across various substrate types.