Characterization of the Cure of Diether-Linked Phthalonitrile Resins

Abstract

New organic resin systems are in constant demand because of the increasing use of fiber-reinforced organic matrix composites to replace metallic components in weight-critical aerospace and advanced marine applications. High temperature capability, low moisture absorption, and improved storage and processing properties are emphasized for new composite matrix materials. Diether-linked phthalonitrile resins recently developed at NRL promise to meet these requirements and are being evaluated as potential candidates for such applications. The linking structure R in the monomers include bisphenol-A, bisphenol-S, bisphenol-A6F, resorcinol, hydroquinone and dihydroxybiphenol. The results of the characterization of cured phthalonitrile resins are presented. This includes their thermal properties from thermal gravimetric analysis and differential scanning calorimetry, spectroscopic properties from the infra-red and nuclear magnetic resonance techniques, and mechanical properties from torsional pendulum analysis and fracture mechanics evaluation. Compared to conventional metallic structural materials, fiber-reinforced organic matrix composites have a very high specific modulus and tensile strength. For this reason, they are being used in many aerospace and marine systems in which weight reduction is an important consideration. This reduction is especially critical for the successful development of new vertical and short take-off and landing (V/STOL) aircraft in order to compensate for the large engines required for vertical lift.Composite materials have been used successfully, and conventional matrix materials such as epoxies are being considered for application in V/STOL systems. Epoxy polymers, however, suffer many shortcomings. They are extremely sensitive to moisture absorption, which causes a large reduction in their glass This chapter not subject to U.S.

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