Currently, there are no high-performance military grade exterior topcoats that are liquid-applied, isocyanate-free and meet the requirements for camouflage, Chemical Agent Resistant Coatings (CARC). The available CARC topcoats in use for Army and Marine Corps ground vehicles, rotorcraft, and ground support equipment all use isocyanates to produce aliphatic polyurethane/polyurea coatings. This includes CARC topcoats qualified to meet the requirements of MIL-DTL-53039E, a single component solvent-borne coating, and MIL-DTL-64159B, a two-component water-dispersible coating. The objective of this project is to develop isocyanate-free resins, coatings formulations, and an understanding of the structure/property relationships that drive CARC coating performance. The novel isocyanate-free topcoats will be validated for performance against current military and commercial corrosion protection and control coatings. Successful development of the isocyanate-free coatings will create a platform technology that may be leveraged for other military applications. These include coatings for Air Force aircraft topcoats and ground support equipment, as well as Naval ship topside and general purpose interior and exterior coatings.
The project team will develop CARC resins and coating formulations based on a novel polyester and multifunctional acrylate, isocyanate-free chemistry. This approach involves resin design, synthesis, and optimization of multi-functional polymers that can achieve high crosslink densities for use in solvent and waterborne coating systems. The novel resins will be formulated to produce coatings that exhibit low gloss, exterior durability, and superior chemical warfare agent (CWA) resistance. Low solar absorbing pigments will be assessed, which would reduce temperature build up on military assets, prolong service life of the coating, and enhance camouflage capabilities. The absorption and adsorption of CWA simulants will be characterized using such methods as atomic force microscopy with infrared spectroscopy and X-ray photoelectron spectroscopy. Coatings performance will be measured against Department of Defense qualified CARC products that meet the requirements of MIL-DTL-53039E and/or MIL-DTL-64159B, as well as commercial corrosion protection and control coatings.
Isocyanate-free advanced military coating systems will improve coating and lifecycle weapon system compliance to environmental and human health regulations compared to current, qualified topcoat systems. A primary goal of this project is to replace the aliphatic isocyanate polymers currently in use to meet MIL-DTL-53039E for CARC topcoats with a resin system based on novel polyester and multifunctional acrylate resin systems. Use of isocyanate chemistries in industrial coatings are associated with respiratory and dermal allergic reactions requiring significant personal protective equipment (PPE) and engineering controls during application. The Sherwin-Williams Company prototypes will additionally minimize or eliminate the use of other known skin sensitizers and other high hazard chemicals. None of the chemicals in the prototype system are classified as respiratory sensitizers under the European Union (EU) classification, labelling and packaging regulation and are not subject to the pending Registration, Evaluation, Authorisation and Restriction of Chemicals restrictions in the EU restricting the use of isocyanates. The prototypes may also allow end-users increased flexibility in the types of PPE and engineering controls required for painting and vehicle maintenance operations compared to isocyanate based systems.