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SynopsisDiaminodiphenyl sulfone (DDS) cured tetraglycidyl-4,4diaminodiphenyl methane (TGDDM) epoxies, whose cure reactions are accelerated by BF3:amine catalysts, are the most common composite matrices utilized in aerospace high performance, fibrous composites. To process reproducible composites requires a n understanding of the cure reactions and how these reactions are modified by the BF,:amine catalysts. In this article we report systematic differential scanning calorimetry (DSC) studies of (i) the constituents of BF3:NH,C2H5-catalyzed TGDDM-DDS epoxies and their mixtures, (ii) the effect of BF3:NH2C2H5 concentration on the cure reactions, (iii) the nature of the catalyzed cure reactions, and (iv) the environmental sensitivity of the catalyst. DSC studies are also reported on the cure reaction characteristics and environmental sensitivity of commercial C fiber-TGDDM-DDS epoxy prepregs.
SynopsisEpoxies suitable for filament-winding fibrous composites must be processible at ambient temperatures, nontoxic, chemically simple, undergo full cure at s 100°C and, also, be tough and exhibit a TB > 120°C. In this paper, we report the cure characteristics, processibility, toxicity, and mechanical and physical properties of a number of amine-cured diglycidyl ether of bisphenol-A (DGEBA) epoxide candidate systems suitable for filament-wound carbon fiber composites. 2,5-Dimethyl-2.5-hexane diamine (DMHDA)-cured DGEBA epoxy was found to be the most promising candidate. The good processibility and thermal properties, togetber with the low cure characteristics of the DGEBA-DMHDA epoxy system, are discussed in t e r m of molecular structure of the arnine molecule. The network structural parameters that control epoxy toughness and subsequent ernbrittlement upon plastic flow are discussed. Evidence is presented for plastic flow-induced thermal and mechanical property deterioration of epoxles as a result of network chain scission.
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