The development of polyetheretherketone (PEEK)-like phthalonitrile (PN) represents a major technological opportunity for use in aerospace, marine, automobile, geothermal, electronic device, and oil rig platform applications.
"The NRL-developed phthalonitrile-based polymeric composites exhibit superior flame resistant, high temperature, and low water absorption properties that do not exist in the current marketplace,” says Teddy Keller, head of the NRL Advanced Materials Section.
PEEK-LIKE PN OFFERS PEAK-LIKE PERFORMANCE WHEN PROCESSED INTO SHAPED FIBER
NRL scientists developed the resin to have loss tangent characteristics and excellent dielectric permittivity, desirable traits in applications that require RF transparency, like high-temperature radomes that shield radar antennae.
Because of its resistance to flammability, impacts, and temperatures up to 500°C, the polymer is ideal for producing improved composites using standard processes such as resin infusion molding (RIM) and resin transfer molding (RTM), according to Keller.
“The many attractive features of the second-generation polyetheretherketone PEEK-like phthalonitriles make these resins excellent candidates for numerous military and domestic applications,” says Keller, who invented the material along with Matthew Laskoski, and Andrew P. Saab. “The fully cured phthalonitrile does not exhibit a glass transition temperature and can be used for structural applications in oxidizing and thermally hostile environments.”
The viscosity of the curing PN composition can be controlled as a function of the curing additive and temperature, according to the NRL. The B-staged prepolymer intermediate can be stored indefinitely under ambient conditions until conversion to the thermoset polymer or use in the fabrication of a composite component.
The polymer’s low water absorption and superior thermo-oxidative stability at high temperatures makes them suitable for use in lightweight automobiles, ships, oil rigs, aircraft, wind blades, high temperature bearings, valves, battery and electronic casings, fire resistant textiles, robotic and autonomous firefighting on ships, ammunition casings and storage containers, and fire-resistant building materials.
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