Photodegradation of Water-Based Acrylic Coatings Containing Silica

By Alison M. Morrow, Norman S. Allen, Michele Edge

The durability of acrylic copolymer systems containing silica as a matting agent is investigated, with particular emphasis on the photodegradation process.

The effects of the photodegradation process on the films are monitored chemically via reflectance FTIR spectroscopy and UV spectrophotometry and monitored physically via gloss levels, optical properties, film thickness, and film smoothness measurements of the cured film.

The findings of this study show that as a result of photooxidation high levels of hydroperoxides are observed. In addition the FTIR results, which are discussed from a mechanistic point of view, indicate that functional group formations and crosslinking reactions which occur as a consequence of photodegradation, play a primary role.

Therefore, this study suggests that silica can reduce the durability of acrylic based formulations and that the extent of this photodegradation ap-pears to be dependent on silica type.