Objective

Polyurethanes (PU) are the preferred polymeric materials for many high-end coating and foam applications for military and civilian use, including most durable topcoats. However, the health hazards associated with the isocyanate compounds used as active building blocks for PU—especially hexamethylene diisocyanate (HDI), which is currently used for non-aromatic PU topcoats—are cause for increasing concern. Other concerns are (1) the potential for exposure to toxic fumes generated when PU are exposed to thermal degradation and fire; (2) added maintenance cost; (3) operation downtime; and (4) generation of hazardous waste as a result of depainting or repainting necessitated by premature changes in the appearance of the coating (e.g., color fading, loss of gloss, chalking) due to environmental exposure.

The research team will develop a non-isocyanate polymerization-crosslinking platform for a high-performance exterior topcoat that (1) eliminates the use of environmentally hazardous isocyanate chemistry and (2) simultaneously improves the weather stability of the topcoat. The team will work together to establish and develop topcoat technology for producing polymers containing the same building blocks incorporated in state-of-the-art PU. These building blocks, easily produced by current manufacturing capabilities, will be polymerized and crosslinked by efficient hydrosilylation reactions instead of isocyanate chemistry. The project will focus on non-aromatic formulations known to be significantly more stable during long-term exposure to ultraviolet (UV) light conditions. The derived topcoats will combine desired features of current topcoats used by the aircraft and other military industries with an alternative binder-setting chemistry that does not require health-hazardous intermediates. The goal will be to achieve the topcoat requirements as identified in MIL-PRF-85285E (Coating, Polyurethane, Aircraft and Support Equipment).