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Physical aging in polystyrene: Comparison of the changes in creep behavior with the enthalpy relaxation
Author(s) -
Roe Ryongjoon,
Millman Gregg M.
Publication year - 1983
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.760230605
Subject(s) - enthalpy , creep , materials science , isothermal process , thermodynamics , polystyrene , annealing (glass) , volume (thermodynamics) , composite material , polymer , physics
Physical aging in polystyrene was studied by annealing samples isothermally (at 22°, 57°, and 93°C) for various lengths of time and measuring the changes in the enthalpy and the flexural creep property. The enthalpy decrease reached a constant value after about 10 hours of aging at 93°C, indicating an apparent attainment of equilibrium, whereas the creep behavior continued to change with prolonged aging even after 10 hours. At room temperature it took about a year of aging to induce a measurable change in enthalpy, while the creep behavior showed changes clearly only after hours of aging. These and other items of evidence indicate that the effect of aging on the creep behavior cannot be interpreted solely in terms of the free volume concept. Thus the hope of being able to predict the mechanical properties of aged polymers from the measurement of specific volume or enthalpy alone is not likely to be realized.