STP658

    Effect of Moisture on Epoxy Resins and Composites

    Published: Jan 1978


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    Abstract

    The effect of absorbed moisture on the properties of six neat epoxy resins (3501-5, 3501-6, 3502, 5208, 934, and NMD 2373) and three epoxy composites (AS/3501-5, B/5505, and hybrid B/5505-AS/3501-5) is explored. Excellent agreement among the diffusion coefficients, activation energy, and activation entropy is observed for all resins with the exception of NMD 2373. Good correlation exists between neat resins and corresponding composites. The effect of a weekly thermal cycle on the diffusivity and equilibrium moisture content of two resins and three composites is presented. Correlations are developed between preconditioning temperature and relative humidity on the magnitude of the anomalous moisture absorption.

    In addition, the effect of absorbed water on the glass transition temperature of six neat epoxy resins and two composites using thermomechanical analysis is considered. The water generally behaves as a classical plasticizer of the epoxy resin, lowering the glass transition temperature as predicted from theory. Comparison between neat 3501-5 resin and AS/3501-5 reveals generally good correlation in Tg at comparable resin moisture levels, but plasticized hybrid boron-graphite/epoxy laminate exhibits a somewhat lower Tg than predicted from theory.

    Keywords:

    epoxy castings, epoxy composites, moisture diffusivity, diffusion kinetics, relative humidity dependence, glass transition temperature, swelling, composite materials


    Author Information:

    Delasi, R
    Senior research scientist, Materials Research Laboratory, and group leader, Structural Mechanics Section, Grumman Aerospace Corporation, Bethpage, N.Y.

    Whiteside, JB
    Senior research scientist, Materials Research Laboratory, and group leader, Structural Mechanics Section, Grumman Aerospace Corporation, Bethpage, N.Y.


    Paper ID: STP34855S

    Committee/Subcommittee: D30.04

    DOI: 10.1520/STP34855S


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