Low VOC Topcoats Using Ultra High Solids Resins

By Dr. Gautam Haldankar, Niel Pfendt

In the North American coatings market, traditional solventborne resins are still used to a large extent, enabled by regulations that allow for the use of certain solvents exempt from restrictions placed on most volatile organic compounds (VOCs) in the United States. The future of the exempt status of parachlorobenzotrifluoride (PCBTF) and tertiary butyl acetate (TBAc) is a concern in certain districts of California, and other regions may follow suit. Coating companies are ramping up their research efforts in formulating paint without exempt solvents.

Researchers are opting to formulate with high solids resins. High-performance acrylic polyols were studied to understand the effect of various resin parameters on coatings performance. A set of resins with 80-90% solids was tested in pigmented topcoat formulations. These topcoats contained VOCs ranging from 200 to 250 g/L, without the use of exempt solvents.

Various conventional and advanced film properties were evaluated, including weathering performance by xenon arc exposure, cure kinetics using infrared (IR) spectroscopy, and crosslink density by dynamic mechanical thermal analysis (DMTA).

Correlation was obtained between coatings performance properties and resin characteristics such as equivalent weight, glass transition temperature, etc. The understanding of structure property correlation offers tremendous value not only for North American coatings researchers but also to the global community.