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  • Remarks on single and multiparameter free volume calculations in physical aging of poly(vinyl acetate) in the T_g-region
    Rychwalski, R. W. ; Delin, Mats ; Kubát, J.
    Free volume plays an important role in the analysis of physical aging, both experimentally and theoretically. In this work, the Doolittle free volume equation and the KAHR model are used to predict ... isothermal responses following temperature down- and up-jumps for poly(vinyl acetate), PVAc, in the T_g-region. The constant B of the Doolittle equation is less than unity when the equation is combined with the Kovacs differential equation for free volume collapse for isothermal contraction predictions. Using B values in the range 0.3 to 0.5 allows good prediction of the isothermal contraction. It is shown that the equation yields aging rates approaching realistic values only for temperatures much below T_g. Isothermal expansion could not be predicted. Volume relaxation kinetics is analysed based on the Doolittle equation and compared with stress relaxation kinetics near T_g, where the slope of the inflexion region is calculated. The transient response of PVAc in the same aging experiments is obtained using the KAHR model.
    Vir: Mechanics of time-dependent materials : an international journal devoted to the time-dependent behaviour of materials and structures. - ISSN 1385-2000 (Vol. 1, no. 2, 1997, 161-180)
    Vrsta gradiva - članek, sestavni del
    Leto - 1997
    Jezik - angleški
    COBISS.SI-ID - 4034331

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