6F-Polyimides with Phenylethynyl Endcap for 315-370 °C Applications

Abstract

6F-Polyimides with a phenylethynyl endcap (HFPE) were fabricated into carbon fiber composites using the standard polymerization of monomer reactant (PMR) approach via the ester/acid route. T650-35/HFPE carbon fiber composites were evaluated against the corresponding T650-35/PMR-II-50 composites with nadic endcap at 315ï370 C (600ï700 F) for their physical and mechanical properties as well as thermo-oxidative stability. In addition, concentrated HFPE monomer solutions were infused into stitched AS4 and T650-35 preforms and their mechanical properties were compared with those of the commercial BMI-5270 composites from cryogenic temperature to 343 C (650 F). The stitched HFPE composites out-performed BMI-5270 composites in terms of property retention at elevated temperature and microcrack resistance during thermal cycling from ï54 to 288 C (ï65 to 550 F). The stitched composites also showed more resistance toward blistering and delamination than conventional laminate composites during a rapid heating rate simulating launch and re-entry of reusable launch vehicles (RLV).

Quantum Mechanical Computations and Microkinetic Modeling to Obtain Mechanism and Kinetics of Oxidative Degradation of a Polyimide

“…For example, fluorination of methylene carbon of MDA should thus prevent the oxidation of MDA, and similarly for the end‐caps. Fluorinated PMR variants are shown to have lower weight loss than the native polymers, in agreement with our conclusions.…”

Fully aromatic macrocycle‐terminated polyimide: synthesis and cross‐linking

“…The amide acid oligomers were synthesized by the reaction of calculated stoichiometric ratios of anhydride (a‐BPDA), amino (2,5‐bis(4‐aminophenoxy)‐biphenyl), and macrocycle (2) in DMAc and subsequently cyclo dehydrated by chemical imidization to obtain macrocycle‐terminated oligomers. Many works showed that reducing average molecular weight by changing the stoichiometry and diamine composition of oligomers owned a profound effect on the processability of the uncured oligomers and T g value after cross‐linking . In this article, the monomers used for synthesizing the polyimide oligomers were varied to study the influences of molecular weight on the cross‐linking properties.…”

High Temperature Shear Strength of T650-35/HFPE-II-52 Polyimide Matrix Unidirectional Composite

“…The carbon fiber tape was obtained from Cytec composites. HFPE-II-52 resin is a NASA-developed polyimide [12]. The samples were prepared by first making a prepreg sheet of carbon fibers and HFPE-II-52 resin.…”

“…The intralaminar shear strength reflects the strength of the matrix and/or the shear strength of the fiber-matrix bond and can be affected by residual stresses [10] and moisture [11]. This study focuses on composites made from T650-35 graphite fibers with HFPE-II-52 matrix, a polyimide developed for use in composite materials [12]. The limited published data available on HFPE-II-52 and its composites include [12][13][14][15].…”

“…This study focuses on composites made from T650-35 graphite fibers with HFPE-II-52 matrix, a polyimide developed for use in composite materials [12]. The limited published data available on HFPE-II-52 and its composites include [12][13][14][15].…”