Novel Matting Agents for Low-VOC Coatings

By Matthew T. Linares

Environmental pressures continue to reduce volatile organic compound (VOC) levels across industry segments and drive formulators to embrace more eco-friendly coatings technologies. Formulators are turning to UV, waterborne, and high solids coatings technologies, as well as the use of exempt solvents and diluents. Each of these technologies presents a new and unique set of challenges when it comes to developing low-gloss coatings.

This article compares a variety of matting agent technologies in three different low-VOC coatings: 100% solids UV, oil-modified polyurethane utilizing exempt solvent D4, and a waterborne acrylic/PUD. The properties of each coating using an array of matting technologies are compared as a guide to help formulators decide which matting agent type is more effective. Two new types of matting agents are presented that are well suited to achieving low-gloss, clear coatings in low-VOC technologies.

The use of 100% solids radiation-curable coatings has continued to grow and evolve as VOC restrictions continue to become more stringent. This coatings segment presents its own unique challenges to achieving low-gloss finishes compared to other coatings segments, because there is typically no sol-vent, little film shrinkage, and varying line speeds and curing conditions. Maintaining good clarity, transparency, and useable viscosity are all challenging due to the high loading of matting agent typically needed.

Matting agents have been developed where particle size, treatment, and structure have been modified to achieve low gloss. In this development, the combination of specific amorphous, synthetic-precipitated silica combined with a specific reacted siloxane surface treatment was found to improve efficacy. Based on this experience, a new product especially designed for low gloss, high transparency, and low viscosity was developed for UV coatings.