STP1302

    Physical and Chemical Aging Effects in PMR-15 Neat Resin

    Published: Jan 1997


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    Abstract

    The objective of this study was to determine whether a shifting approach can be used to account for both chemical and physical effects during long-term aging of high temperature polyimide thermoset polymers, such as the commercial material PMR-15. Stress relaxation curves measured after aging at 316°C for times up to 800 h could be shifted to form a master curve. The horizontal shift factors were found to increase with increasing aging time, consistent with a reduction in molecular mobility that occurs as a result of either physical aging or increased cross-linking. There was a correlation between the vertical shift factors and cure related chemical changes that cause Tg to increase and mass to decrease. Aging effects were partially reversed by heating the aged specimen above its glass transition temperature, indicating that a large portion of the aging is physical in nature. Specimens aged in nitrogen had a larger reversible component than specimens aged in air.

    Keywords:

    stress relaxation, viscoelastic, polyimide, physical aging, chemical aging


    Author Information:

    Kamvouris, JE
    National Research Council research associate, materials engineer, and materials engineer, NASA Lewis Research Center, Cleveland, OH

    Roberts, GD
    National Research Council research associate, materials engineer, and materials engineer, NASA Lewis Research Center, Cleveland, OH

    Pereira, JM
    National Research Council research associate, materials engineer, and materials engineer, NASA Lewis Research Center, Cleveland, OH

    Rabzak, C
    Aerospace engineer, NYMA Inc., Cleveland, OH


    Paper ID: STP11378S

    Committee/Subcommittee: D30.05

    DOI: 10.1520/STP11378S


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