M. Laskoski, T.M. Keller
Naval Research Laboratory,
Keywords: composite, fire resistance, high temperature
Summary:A new oligomeric 2nd generation resorcinol, PEEK™-like phthalonitrile resin has been developed via a cost-effective methods and is being transitioned to an industrial scale. The phthalonitrile monomer used to prepare composite components exhibits viscosities much easier to process when compared to the 1st generation resorcinol-based phthalonitrile and is comparable to current resin technologies at their respective processing temperatures. When postcured to elevated temperatures, the composite exhibited excellent dynamic mechanical, thermal, mechanical and flammability properties over a large temperature range. Several phthalonitrile resin systems were examined in our studies and the heat release of the composite samples was tested in accordance with ASTM E1354, which measures the ignitability, heat release rate, mass loss rate, and combustion product generation rate of a material exposed to a specified irradiance level. From this data, we identified phthalonitrile composite formulations that will pass the requirements for MIL-STD-2031 for use in the most extreme fire environments. After exposure to elevated temperature oxidative aging, the composites exhibited very low weight loss and high mechanical strength retention. The new phthalonitrile composite shows low flammability parameters when compared to other thermosetting polymers and offers promise of superior fire performance for potential ship and submarine applications and even to the commercial sector as fire resistant structural materials. When fully cured, some important features of the new composite include the absence of a Tg ,which translates to minimal loss of structural integrity at elevated temperatures,and excellent thermo-oxidative, low flammability, good dielectric and low water absorption properties. References: 1. “Improved Synthesis of Oligomeric Phthalonitriles and Studies Designed for Low Temperature Cure” Laskoski, M; Neal, A.; Keller, T. M.; Dominguez, D. D.; Klug C. A.; Saab A. P. J. Poly. Sci. A Poly. Chem., 2014, 52, 1662-1668. 2. “Oligomeric Bisphenol A-Based PEEK-Like Phthalonitrile - Cure and Polymer Properties” Keller, T. M.; Dominguez, D. D.; Laskoski, M. J Poly Sci Part A Poly Chem, 2016, in press. 3. “Synthesis of and Curing Additives for Phthalonitriles” Keller, T. M.; Laskoski, M., No. 8,981,036; issued March 17th, 2015.