DuPont Protection Technologies (Richmond, Va., USA) presented information on the company’s new Nomex XF product at CompositesWorld’s High Performance Composites for Aircraft Interiors Conference, held Oct. 2-3 in Seattle, Wash. The new flame barrier solution meets the latest Federal Aviation Regulations FAR 25.856 (a) and (b), with more stringent requirements aimed to improve protection against fire intrusion into aircraft interior cabins.
Nomex XF is used as a layer in the covering film for aircraft thermal/acoustic insulation blankets, which are attached to the underside of aluminum fuselage panels. Nomex XF acts as a refractory (heat-resistant) layer, interleafed between a lightweight outer protective moisture barrier and a lightweight inside scrim-reinforced thermoplastic. This thermoplastic enables the fiberglass batting interior of the blanket to be contained within heat-sealed edges and aids in sufficient mechanical strength to resist damange during installation.
Nomex XF can withstand a direct flame >2000˚F/1093˚C, aiding in the insulation blanket’s performance, showing no burn-through after 10 minutes when tested per FAR 25.856 (b), more than doubling the 4-minute FAA requirement.
Cover films including Nomex XF exceeded FAA and OEM requirements in FAR 25.856(a) testing as well. In this Radiant Panel Test, insulation blankets must show <2-inch flame propagation from the point of flame contact on the cover film and an after-flame time (i.e., time to self-extinguish after removal of the source flame) of less than 3 seconds. Films with Nomex XF exhibited flame propagation of less than 1 inch and after-flame time of 0 second.
DuPont claims that Nomex XF films can reduce weight up to 33 percent compared to other commercially available products, and have demonstrated higher heat seal seam strengths and interlayer bond strengths as well as equal or better puncture and burst strengths. Nomex XF-based cover films are reportedly stable in humid and wet environments, do not wick water, and absorb equivalent or less moisture than competitive burnthrough-resistant films.
DuPont is working directly with aircraft manufacturers and their suppliers to evaluate Nomex XF for use in current and future airframes. It also announced on June 19 at the 2013 Paris Air Show that its work with Holmestrand, Norway-based Nordisk Aviation — a division of commercial aerospace and defense contractor AAR Corp. (Wood Dale, Ill.) — to develop a Fire Resistant Container (FRC) capable of containing a fire for up to six hours of fllight. The 485-ft3 /13.7m3 main deck container passed testing at third-party independent facility Intertek (San Antonio, Tex.) and offers weight savings vs. traditional argon-based foam fire-suppression systems used on cargo planes.