prevention of tio2 crowding through steric hindrance by silane coupling in organic coatings

This study aimed to reduce tio2 crowding through steric hindrance by grafting 3-methacryloxypropyltrimethoxysilane (mps) onto the pigment surface. this was achieved using various tio2/mps mass ratios in dispersion formulations and characterized by ftir and tga analyses. characterizations revealed the most efficient grafting for the tio2/mps ratio of 100/10 (labeled tt3). an optimum particle size of 250-350 nm for opacity was obtained after 30 minutes of tt3 dispersion, resulting in the maximum number density of 47.45 % within this size range. the tt3 dispersion demonstrated high lightness and opacity, with minimal changes in surface properties compared to untreated and other mps-grafted tio2 dispersions, suggesting its advantageous use. the impact of pigment volume concentration (pvc) on pigment spacing was examined using topcoats with pvc levels of 7, 11, and 13 %, incorporating tt3 and untreated tio2 dispersions. the lightness and opacity results indicated that lower pvc levels allowed wider spacing between pigment particles in dry films. additionally, untreated tio2 pigments exhibited increased crowding at equivalent pvc levels compared to the tt3 dispersion, while a rise in pvc did not diminish opacity or lightness in dry films with tt3, highlighting the even pigment distribution. notably, dry films of the topcoats with tt3 or untreated pigment dispersions revealed that the tt3-containing topcoat at 30 µm for a given pvc exhibited almost identical properties to those of the topcoat containing untreated tio2 dispersion at 55 µm. thus, mps grafting facilitated reduced pigment usage in paint formulations and lower paint consumption per unit area, decreasing volatile organic compound emissions.