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Universal Pigment Package for MIL-PRF-24635 Polysiloxane Topside Coatings 

Jimmy Tagert, Erick Iezzi, James Martin, Sumathi Gulati

Polysiloxane coatings qualified to MIL-PRF-24635E are required to contain infrared (IR) reflecting pigments to meet the low solar absorption (LSA) testing requirement. Coating manufacturers are allowed to use any combination of IR reflecting pigments as long as they meet the minimum performance requirements in the specification (e.g., LSA, accelerated weathering, metals content, etc.). This has resulted in coatings that visually appear different out of the can and gradually fade to different colors due to ultraviolet (UV) light exposure based on the pigments selected. To resolve this problem, the Naval Research Laboraroty (NRL) and the Naval Sea Systems Command (NAVSEA) determined the best approach was to develop a universal pigmentation requirement for MIL-PRF-24635 that would specify the chemical composition of the pigments used in the polysiloxane coatings. This would ensure all coating manufacturers would be using similar pigments, which should lead to similar performance. This paper provides the testing results of various pigment packages tested by NRL that lead to down selection of the best performing pigment combination for the universal pigment package. The work was sponsored by the NAVSEA Paint Center of Excellence Program starting in October 2015 and ending in September 2016. The work was performed by NRL Code 6138 in Washington, DC. 1 Naval Research Laboratory, Code 6138, Washington, DC 2 Naval Research Laboratory, Code 6132, Washington, DC 3 Excet Inc., Springfield, VA