Acrylate Monomer-Free or VOC-Compliant Ultraviolet-A Radiation-Curable Technology for Automotive Refinish Clearcoat

By Michael Jeffries, Charles Gambino, Joe Pierce

Ultraviolet (UV)-curable coatings have experienced growth in many market areas. However, penetration into the automotive refinish market has been relatively slow. One reason has been the safety concern from the end user about use of UV radiation. RadTech International set up an automotive refinish focus group to help address the issues relating to the use of UV tech­nology for this market area. This included the promotion of UV-A curable technology and its safe use. In 2001, the concept of using UV-A lamps to cure a primer system for the refinish market was introduced.

UVA-curable coatings have since been experiencing growth in automotive refinish applications. They have many advantages over conventional coatings systems in that they can cure fast and are 1K. Current developments in UV-A curable technology have yielded coatings that are highly reactive and also minimize residual unsaturation in the cured ,coating. Despite this, the use of these resins in automotive refinish clearcoats or spot repair is still limited.

The main reason has been the difficulty in the sanding and buffing of the clearcoat due to the difference in coatings properties of the refinish coatings and the OEM coating being repaired. Properties of concern are the hardness and glass transition temperature (Tg). Since 2K polyurethane technology is widely used in the automotive refinish market, if the UV-A curable refinish coating could mimic its properties then the system will blend well. This led to the development of two acrylate monomer-free aliphatic urethane acrylate resins.