Cure-On-Demand Conductive Sealant for Rapid OML Repair

ABSTRACT: The use of sealants in aircraft assembly and outer mold line (OML) repair is widespread. Sealants are used to wet-install fasteners, for sealing overlapping (faying) surfaces, for butt joints between panels, and for seam (fillet) sealing. Aerospace sealants are typically two-component polysulfide or polythioether compositions that can cure by oxidation or by crosslinking with epoxides, and require several hours to cure to a tack-free state. These long tack-free times are especially costly for OEM manufacture and repair of aircraft in terms of delayed cure. The ideal sealant would exhibit a long open time and then cure on-demand within a short period of time. In the Phase I, Luna has demonstrated the feasibility of a novel cure-on-demand chemistry with long open time and rapid cure. The Phase I also established that a cure-on-demand conductive sealant can achieve excellent post-cure performance in terms of elongation, resistivity, fluid resistance, and adhesion. During the proposed Phase II effort, Luna will continue to improve on this sealant material to fit the AF needs for rapid cure time in a high performance sealant. Luna will also address issues related to sealant application, scale-up, and commercialization/technology transfer. BENEFIT: The primary commercial application resulting from this program would be a conductive cure-on-demand sealant, that will dramatically decrease the time needed to cure sealants during OEM and repair activities. This sealant could potentially serve as a gap filler on a wide variety of aircraft joints and seams for both military and commercial aircraft. In addition, the resin chemistry developed under this program could also be extended to a wide family of cure-on-demand sealants, adhesives, and coatings.