Aerospace and Aviation Certifications

Designed to mitigate the worst effects of fires, fire retardant materials play a particularly important role in aircraft construction. Used in aircraft, epoxies and silicones must maintain their primary role as adhesives or coatings while exhibiting resistance to heat and flame in accordance with government and industry specifications. Master Bond’s series of flame retardant epoxies and silicones comply with specifications for flame resistance and reduction of smoke density and toxic emissions.

Can an adhesive maintain its strength when bonding titanium to carbon-carbon composites under extreme temperature and harsh conditions? This is precisely what researchers1 from QSS Group, Inc., the Ohio Aerospace Institute and the NASA Glenn Research Center were determined to find out. They tested multiple formulations, and discovered that Master Bond EP45HTAN proved to be ready for the challenge.

Master Bond EP29LPSPND-3 is a two component, non-drip epoxy compound with a paste consistency that can be used for bonding and sealing applications. The system is electrically non-conductive and thermally insulative, with a thermal conductivity of approximately 0.2 W/(m•K) at room temperature. It withstands cryogenic temperatures and is serviceable in the range from 4K to 250°F. EP29LPSPND-3 features a coefficient of thermal expansion of 45-50 x 10-6 in/in/°C, a tensile strength of 6,000-8,000 psi, and a Shore D hardness of 70-80. This system has a volume resistivity exceeding 1015 ohm-cm at 75°F and a dielectric constant of 4.2 at 60 Hz. A key performance attribute is its ability to withstand temperature cycling even at cryogenic levels. EP29LPSPND-3 has a mix ratio of 100:65 by weight with a long working life after mixing; a 100-gram batch will yield an open time of greater than 5 hours at 75°F. The color of Part A is clear-translucent, and Part B is amber-clear; it cures clear when applied in thin sections despite being a paste, with a refractive index of 1.56 at 589 nm. The recommended cure schedule is either 12-18 hours at 130-150°F or a faster 5-10 hours at 150-165°F. EP29LPSPND-3 is available in ounce jar kits, half pint kits, pint kits, quart kits, and gallon kits.

EP93FRHT was developed for various bonding, sealing, coating, and encapsulation applications in aircrafts, where stringent requirements for flame retardancy, smoke emission, and toxicity levels have to be met.To prepare for the Airbus tests, castings of Master Bond EP93FRHT epoxy were made. The first test is the vertical ignition test (conducted in accordance with Airbus AITM 2.0002B, Issue 2 for specification ABD0031, Issue F, Section 7.1.2). The casting specimen was exposed to certified pure bottled methane for 12 seconds. The results show that it took under 1 second to extinguish the flames, well under the allotted 15 seconds permitted by the test.The second part of this test measures how far the flame has spread. Again, EP93FRHT depicts a burned length of just over 7 mm. Once again, well under the maximum allowed of 203 mm. Airplane interiors that might be tested for the 12 second vertical burn test include carpeting and other floor coverings, upholstery, seat cushions, and air ducting.The next Airbus test is the optical density of smoke generated by solid materials (conducted in according with AITM 2.0007B, Issue 3 for specification Airbus Document ABD0031, Issue F, Section 7.3.2). In this test, the epoxy casting is exposed to a flame for 60 seconds after which a successful result would show that the smoke being generated is below the threshold of 200 specific optical density (Ds). Master Bond EP93FRHT passes with flying colors, with a Dmax of 137. (Please refer to chart below.) This Airbus test may be used on interior wall panels, aircraft doors, and stowage compartments.Specific Optical Density, Ds of Smoke Generated by Solid MaterialsTime from Initiation (seconds)Specimen: EP93FRHT0-60090171203615063180103210116240137Time to Dmax (seconds)3:59.6Last, we have the toxic gas analysis of the smoke that was generated. At the end of the smoke test, 4 minutes after initiation, the specimen is tested for toxicity to certain reactive gases, like carbon monoxide, hydrogen chloride, nitric oxides, sulfur dioxide, hydrogen cyanide and hydrogen fluoride. In this next chart, you can see the acceptance criteria for toxicity specified by the Airbus test, ABD0031 Issue F, Section 7.4 per AITM 3.005, Issue 2,and that the values of the Master Bond epoxy fall well below each.Toxic Gas Analysis of Smoke: Flaming exposure 4 minutes after start of AITM 2.0007B NO+NO2HCNSO2HF 47.2-4-Average49.31550 (No Indication)Standard Deviation10.5n/a1n/aMaxiumum Allowed100150100100Master Bond EP93FRHT is a two component epoxy that can be used as an adhesive, sealant and encapsulating system. It also is widely used for potting electronic components. To learn more about this specialty product, please contact a technical advisor today.*Disclaimer: The results of these tests were determined under controlled laboratory conditions and are not necessarily representative of the behavior of the material under actual fire conditions. However, the results of these tests may be used as elements of a fire risk assessment that takes into account all of the factors that are pertinent to its end use.