There are currently no commercially-available powder coatings that meet the military's specification MIL-PRF-32348, Powder Coating, Camouflage Chemical Agent Resistant Systems, Type III, Class I & II. The current liquid applied chemical agent resistant coating (CARC) topcoats supplied by all coatings vendors emit about 5.2 million lb per year of organic solvents. Sherwin-Williams has experience in lowering volatile organic compound (VOC) emissions and had commercialized water dispersible CARC topcoats. These coatings lowered VOC levels from 3.5 lb per gallon in solvent-borne CARC to 1.8 lb per gallon in water dispersible CARC.
The objective of this project is to establish a fundamental understanding of coatings materials and their interactions to develop a CARC powder topcoat.
The researchers will develop the CARC powder topcoat coating based on polymer blends formulated with fillers and pigments. This approach involves the design, synthesis, and optimization of functionalized polymers. These new polymer technologies will be coupled with a formulation strategy that will maximize light scattering efficiency and crosslink density so as to produce ultra-low gloss, highly durable, chemical agent resistant coatings. Cure temperatures of 350°F or less, will be explored. Spectroscopic and physical characterization methods will be used to study the structure and property relationships of formulation materials and resulting coatings, and the interactions of powder CARC topcoat with current pretreatments and CARC primer and topcoat technologies. Design of Experiments methods will be utilized to enable optimization of powder coating performance.
Developing this chemical agent resistant coating powder topcoat will have tremendous environmental benefits for the Department of Defense (DoD). Current solvent-borne and water dispersible CARC topcoats from all suppliers contribute approximately 5.2 million lb of VOCs and hazardous air pollutants (HAP) to the environment. These emissions will be greatly reduced by a powder coating. Powder coatings are solid, free-flowing, solventless dry particulate systems. Eliminating solvents within the coatings and those used for cleanup should also improve worker safety and reduce time and costs associated with the handling and disposal of hazardous wastes. In general, powder coatings have the capability of being recycled.
Powder coatings require stringent methods for surface pretreatment. This has the environmental benefit that it should provide an improved corrosion protective surface, thereby supporting the DoD Corrosion Prevention and Mitigation Plan, while maintaining focus on warfighter survivability.
By the researchers developing a fundamental understanding of the raw materials that comprise the coatings and their interactions, the DoD, the non DOD industrial community, and the academic community will benefit from this knowledge being available for future powder coatings requirements.
Giles, S. L., Heller, N. W., Clayton, C. R., Walker, M. E., Wytiaz, M. J., & Wynne, J. H. (2016). Novel Methods of Producing Low Reflectance Coatings Utilizing Synergistic Effects of Polymer Phase Separation. ACS Applied Materials & Interfaces.
Heller, N. W., Clayton, C. R., Giles, S. L., Wynne, J. H., Walker, M. E., & Wytiaz, M. J. Characterization of immiscibly blended polyurethane coatings part 1: selective staining for enhanced micro-Raman spectroscopy. Journal of Coatings Technology and Research, 1-13.