Structural Adjustment of In-Situ Surface-Modified Silica Matting Agent and Its Effect on Coating Performance

摘要

A series of silica surface-capped with hexamethyldisilazane (denoted as H-SiO2) were prepared by liquid-phase in-situ surface-modification method. The as-obtained H-SiO2 was incorporated into acrylic amino (AA) baking paint to obtain AA/H-SiO2 composite extinction paints and/or coatings. N-2 adsorption-desorption tests were conducted to determine the specific surface area as well as pore size and pore volume of H-SiO2 . Moreover, the effects of H-SiO2 matting agents on the physical properties of AA paint as well as the gloss and transmittance of AA-based composite extinction coatings were investigated. Results show that H-SiO2 matting agents possess a large specific surface area and pore volume than previously reported silica obtained by liquid-phase method. Besides, they have better dispersibility in AA baking paint than the unmodified silica. Particularly, H-SiO2 with a silica particle size of 6.7 mu m and the dosage of 4% (mass fraction) provides an extinction rate of 95.2% and a transmittance of 79.3% for the AA-based composite extinction coating, showing advantages over OK520, a conventional silica matting agent. Along with the increase in the silica particle size, H-SiO2 matting agents cause a certain degree of increase in the viscosity of AA paint as well as a noticeable decrease in the gloss of the AA-based composite extinction coating, but they have insignificant effects on the hardness and adhesion to substrate of the AA-based composite coatings. This means that H-SiO2 matting agents could be well applicable to preparing low-viscosity and low-gloss AA-based matte coatings.