Some market areas desire light- and weather-stable tough, elastomeric, thick section coatings that could be pigmented to various shades. For example, the automotive industry would like to use this approach to manufacture truck bed linings that match the color of the remainder of the vehicle. There are several approaches that could satisfy this need. Critical to the market are the various cost / benefit scenarios involved with these approaches. A new approach using a modified aliphatic elastomer as a stand-alone coating or in a composite approach using under layers of traditional spray polyurethane-ureas over-coated with a system based on aliphatic isocyanates is the subject of this paper. We will review the chemistry, formulation approaches, application equipment, and physical properties of traditional systems and compare these to the new modified aliphatic system and composite. Special emphasis will be on the modified aliphatic, which consists of polyesters, polyaspartic esters, and adducts based on hexamethylene diisocyanate.

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Thick film coatings (TFCs) are currently used for a variety of protective applications from marine buoys and tank farm secondary containment to bridge deck moisture barriers. These applications typically use non-light stable coatings because of their proven history of performance. A recent internet survey of coating suppliers showed that there are currently about 40 suppliers of light-stable thick film coatings. In all cases these are based on polyurethane and/or polyurea technology. The primary source of light stability for these systems is the aliphatic isocyanate that they are based on. The replacement of aromatic isocyanate e.g. MDI (methylene diphenyl diisocyanate) with aliphatic isocyanates based on e.g. HDI (hexamethylene diisocyanate) or IPDI (isophorone diisocyanate) leads to the most significant improvement in light stability in TFCs. Aliphatic polyisocyanates have been used in high performance coatings for many years in the automotive OEM and refinish, industrial, and construction/maintenance markets. The primary focus of this paper is light stable elastomeric coatings and the latest resin developments that can enhance performance and applications. These same resins can also be used to create light stable rigid thick film coatings such as gel coats, or fiber composite binders.

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