Historically, the DoD has used qualified polysulfide primers on large aircraft. These primers demonstrate excellent flexibility, elongation and do not crack when exposed to high flexures encountered during pressurization, landings and takeoffs.  The implementation of more stringent emission regulations restricted the use of the polysulfide primer due to excess volatile organic compounds (VOC) required for spray application. Past efforts to manufacture a compliant polysulfide primer have proven unsuccessful due to problems arising from a slow cure under high humidity conditions and reduced weatherability due to unreacted sulfur compounds in the primer interacting with the topcoat. 

In response to the need for a high performance coating, Infoscitex has developed a primer that meets physical/chemical durability, corrosion resistance performance and environmental regulatory requirements. The sprayable primer is based on epoxy modified polysulfide chemistry impervious to moisture during application. The Infoscitex approach to developing a flexible aircraft primer was to choose a base resin system that combined the desired flexibility of a polysulfide coating with the rapid cure and adhesion of epoxy-based chemistry.  Infoscitex has demonstrated these inherent advantages of the modified resin system, focusing first on developing a primer that exhibited excellent adhesion and flexibility.  The primer demonstrated excellent adhesion to treated aluminum substrates before and after exposure to various operational fluids, including hydraulic fluid and lubricating oil.  Panels coated with the epoxy modified polysulfide demonstrated excellent flexibility (greater than 60% elongation) both at room temperature and low temperature (-50 °C).  This presentation will review the results of research and development efforts to date, including corrosion testing of the primer with various inhibitor packages and single impact jet apparatus (SIJA) testing.