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Multiordering parameter models of volume and enthalpy recovery generalized to treat physical aging; a quantitative investigation
Author(s) -
Chen Y. P.,
Aklonis J. J.
Publication year - 1987
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.760271703
Subject(s) - materials science , thermodynamics , relaxation (psychology) , volume (thermodynamics) , enthalpy , range (aeronautics) , generalization , distribution (mathematics) , statistical physics , creep , stress relaxation , mathematics , physics , mathematical analysis , composite material , psychology , social psychology
Multiordering parameter models have been quite successful in rationalizing volume and enthalpy behavior of glasses subjected to various thermal histories in the glass transition range and even at lower temperatures. In the past we suggested a generalization of such models to encompass what is now termed physical aging, i.e., recovery as monitored by mechanical experiments such as creep and stress relaxation. Our initial investigation indicated qualitative agreement between the generalized model and experimental behavior. We have now more completely investigated this area and found a convenient approximation through which behavior can be calculated in most situations without using a distribution of mechanical relaxation or retardation times. Using this technique, we find that essentially quantitative agreement between this model and experimental results is possible only when a very sharp distribution of volumetric recovery times, like that of a single ordering parameter model, is used, Broader distribution functions result in aging behavior which is much more sluggish than observed experimentally. This result is particularly disturbing since such sharp distribution functions have been shown to be incompatible with direct observations of volume recovery.