Flame retardant tapes in ‘flyaway’ applicationsOctober 13, 2020
At Saint-Gobain Tape Solutions, a “flyaway” application is defined as any end use where the vehicle will indeed fly away. The aerospace industry has demanding expectations of the products used for fixed-wing aircraft, helicopters and spacecraft, because when passenger safety is at stake, there is zero tolerance for defective or underperforming materials.
This is especially true for often undervalued tape and silicone materials. Flyaway material solutions must meet various challenging criteria, with high performance in terms of extreme temperatures, dielectric strength, adhesion, pealability – or, most critically – flame retardancy.
Saint-Gobain adhesive tapes and silicone rubbers meet many regulatory requirements for FAA and UL, as well as the specification requirements of OEMs, the military, NASA and other manufacturers. In addition to its wide portfolio of trusted adhesive material solutions, Saint-Gobain is known for its product development and customization abilities, which ensure that customers receive high-quality materials with the required specifications and configurations.
Saint-Gobain is the technology leader in flame retardant material solutions for common flyaway applications such as gasketing, insulating and sealing; wire harness assembly; and cabin flooring. With expertise of the industry, standards and adhesive science, Saint-Gobain helps busy engineers make decisions about an important but underestimated technology.
Safety and standards
Fire retardancy is paramount to aircraft safety. Retardance is typically a characteristic added to materials by chemical additives that naturally extinguish or slow the growth of fire, as per the National Institute of Environmental Health Sciences.
There is the obvious danger of an unchecked flame endangering the airworthiness of the aircraft. One of the most common risks for such a fire are the miles and miles of electrical wiring, so a fire-retardant tape with high dielectric strength can prevent a small electric arc from becoming a catastrophe. Additionally, fires create smoke, and even a small amount of smoke can overwhelm passengers and crew in an aircraft interior, forcing an emergency landing.
Since fire retardancy is so critical, many industrial standards have sought to address it. UL tests foams and tapes for specifications such as ease of ignition, burning rate, flame spread, fuel contribution and intensity of burning, among others. In the commercial aviation space, this is most notably the standards published by the OEMs Boeing and Airbus — together these standards represent a 95% market share. In addition, FAA standards must also be met. Meanwhile, the U.S. military has its own guidelines. The end result is a network of overlapping standards that can sometimes be difficult to navigate.
The four main test standards referenced by Saint-Gobain are:
1. Tests for Flammability of Plastic Materials for Parts in Devices and Appliances: ANSI/UL 94 dated June 27, 2020, 6th Ed.
2. Code of Federal Aviation Regulations part 25 and 26 rules, Advisory Circulars (AC), and Policy Statements (PS); 25.583, Compartment Interiors
3. OEM Specifications (Boeing and Airbus)
4. Military Specifications
These standards guide the development of Saint-Gobain materials, which can be customized or converted to a customer’s exact specifications. Each of these flyaway applications requires a dedicated product with application competence and flame retardant capability.
Gasketing, insulating and sealing
Saint-Gobain Norseal® Silicone Rubbers meet key aerospace standards and have a proven history in flyaway applications. Norseal Silicone Rubber products have been chemically engineered for flame retardance, low outgassing and low toxicity, making them ideal for gasketing, thermally insulating and sealing doors, instruments, electronics, windows and more. The various silicone rubber configurations offer a range of densities, including lightweight options, a primary concern for the aviation industry where each ounce adds to fuel costs.
Norseal silicones can be supplied as a foam, solid, reinforced-solid or sponge material. The ability to convert and add pressure-sensitive adhesives means Norseal products arrive ready for manufacturing.
Wire harness assemblies
Saint-Gobain CHR® Adhesive Tapes are also common in many flyaway applications. Wide-body jumbo jet airliners contain up to 170 miles of electrical conduit, with the wires bundled and mechanically fastened in raceways or plenum space. These wire bundles are subject to the shock and vibration of takeoff, taxiing, flying and landing, which impart stress and abrasion to the conduit and wire insulation.
CHR Tapes are designed for wire harness assembly needs, such as for splicing of insulation films or to improve abrasion resistance for the locations where wires are secured throughout the assembly. Saint-Gobain engineers CHR Tapes with backing materials of polytetrafluoroethylene (PTFE), PTFE-coated para-aramid fabrics, polyimide and glass cloth. These materials supply the high abrasion, excellent dielectric strength and extreme temperature resistance wire conduits require. They are also flame retardant or resistant.
Once coupled with a specially formulated acrylic or silicone adhesive, CHR Tapes are a powerful solution for wire harness assemblies.
Saint-Gobain Biolink® Carpet Tapes have been developed specifically to meet the demands of OEM aircraft customers, such as Airbus and Boeing. These double-sided, dual-adhesive acrylic carpet tapes are high-performance components, that can serve as a moisture barrier or a means to secure aircraft carpet or flooring.
They also have removable, residue-free adhesives for when carpeting needs to be replaced.
This makes it ideal for installing aircraft carpeting or non-textile flooring (NTF), which must withstand the daily traffic of hundreds of passengers, but is typically replaced annually to keep cabins comfortable and clean. The dual-adhesive provides maximum adhesion to the carpeting substrate on the one side, and the right combination of strong adhesion with clean removability on the side adhering to the composite floor.
A partner for flyaway success
Saint-Gobain specializes in helping aerospace OEMs and suppliers find the materials that meet their demanding applications while also satisfying regulatory compliance. This is possible only through the technical expertise of Saint-Gobain engineers and an integral understanding of the standards needed to ensure tapes are airworthy.
For example, something as simple as a carpeting change can lead to untold disruption without careful planning. As carpeting and NTF materials evolve, these may require customized adhesive solutions to supply the performance OEMs have come to rely on. Saint-Gobain will work with customers to engineer and deliver the material solutions they need.
For more information on tape technologies and for flyaway applications, visit the Saint-Gobain Tape Solutions website.