Synthesis of a high-fastness cationic silica/fluorine-free acrylate water repellent and its application in fabrics

Abstract

Appropriate surface roughness can enhance the hydrophobicity of low-surface tension materials. SiO₂ can increase the roughness of hydrophobic films. However, it is negatively charged and incompatible with cationic water-repellent emulsions. In this paper, a SiO₂/fluorine-free acrylate water-repellent emulsion (SKD⁺/FFA) in which cationic modified SiO₂ built a chemical bond with the acrylate component was synthesized and coated on fabric to achieve high fastness and excellent hydrophobicity. SiO₂ covered with polymer brushes containing cationic groups and carbon–carbon double bonds (SKD⁺) was obtained after the modification of SiO₂ with 3-methacryloxypropyltrimethoxysilane (KH570), 2-(dimethylamino) ethyl methacrylate (DMAEMA), and 3-bromopropene in order. SKD⁺, methyl methacrylate (MMA), butyl acrylate (BA), and octadecyl acrylate (SA) undergo a free radical polymerization reaction and can form a cationic SiO₂/fluorine-free acrylate emulsion (SKD⁺/FFA). FT-IR spectra suggested that the modification of SiO₂ was successful. The mean particle size and electric potential were tested by dynamic light scattering. The core–shell structure of SKD⁺/FFA was characterized by TEM, and the surface morphology of the coated fabric was investigated via SEM. The results indicated that the modified SiO₂ was well dispersed in acrylate emulsion and was evenly distributed on the fabric surface due to the positive charge and chemical bonding with acrylate. Compared with FFA without SiO₂ (FFA), SKD⁺/FFA films had a higher thermal decomposition temperature and a slower decomposition rate. Fabric coated with SKD⁺/FFA was better than the one coated with FFA in whiteness and hydrophobicity (water repellency), showing good water repellency after 50 launderings.