Dispersion of “guava-like” silica/polyacrylate nanocomposite particles in polyacrylate matrix

Abstract

A series of “guava-like” silica/polyacrylate nanocomposite particles with close silica content and different grafting degrees were prepared via mini-emulsion polymerization using 3-(trimethoxysilyl)propyl methacrylate (TSPM) modified silica/acrylate dispersion. The silica/polyacrylate composite particles were melt-mixed with unfilled polyacrylate (PA) resin to prepare corresponding silica/polyacrylate molded composites and the dispersion mechanism of these silica particles from the “guava-like” composite particles into polyacrylate matrix was studied. It was calculated that about 110 silica particles were accumulated in the bulk of every silica/polyacrylate composite latex particle. Both the solubility tests of silica/polyacrylate composite latex particles in tetrahydrofuran (THF) and the section transmission electron microscope (TEM) micrographs of silica/polyacrylate molded composites indicated that the grafting degree of silica particles played a crucial role in the dispersion of silica/polyacrylate composite particles into the polyacrylate matrix. When the grafting degree of polyacrylate onto silica was in a moderate range (ca. 20%–70%), almost all of silica particles in these “guava-like” composite particles were dispersed into the polyacrylate matrix in a primary-particle-level. However, at a lower grafting degree, massive silica aggregations were found in molded composites because of the lack of steric protection. At a greater grafting degree (i.e., 200%), a cross-linked network was formed in the silica/polyacrylate composite particles, which prevented the dispersion of composite particles in THF and polyacrylate matrix as primary particles.

Keywords

silica / polyacrylate / nanocomposite / dispersion