Novel Improved PMR Polyimides.
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION CLEVELAND OH LEWIS RESEARCH CEN TER
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N-phenylnadimide modified PMR resins and composites were investigated with the objective of improving the overall flow characteristics of PMR-15 type resins without compromising composite properties. A series of N-phenylnadimide PN modified PMR polyimide composites reinforced with Celion 6000 graphite fibers were investigated. The improved flow matrix resins consist of N-phenylnadimide PN, monomethyl ester of 5-norbornene-2, 3-dicarboxylic acid NE, dimethyl ester of 3,3,4,4-benzophenonetetracarboxylic acid BTDE, and 4,4-methylenedianiline MDA. Five modified PMR resin systems were formulated by the addition of 4 to 20 mole percent N-phenylnadimide to the standard PMR-15 composition. These formulations and the control PMR resin were evaluated for rheological characteristics. The initial thermal and mechanical properties of the PN modified PMR and the control PMRCelion 6000 composites were determined. The elevated temperature flexural and interlaminar shear properties and the weight loss characteristics of the PMR composites isothermally exposed at 600 deg F in air for 1500 hours were evaluated. In addition, the effects of hydrothermal exposure on the glass transition temperatures and the elevated temperature flexural properties of the PMR composites were also investigated. The results of this study clearly showed that the addition of N-phenylnadimide to PMR-15 significantly improved the resin flow characteristics without sacrificing the composite properties. This study further revealed that concentrations of 4 and 9 mole percent PN appear to improve the therm-oxidative stability of PMR composites. jg p3
- Organic Chemistry
- Polymer Chemistry
- Laminates and Composite Materials