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The effects of thermal history on the density and mechanical properties of poly(methyl methacrylate)
Author(s) -
Hutchinson J. M.,
Bucknall C. B.
Publication year - 1980
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.760200302
Subject(s) - materials science , poly(methyl methacrylate) , thermal , composite material , methacrylate , methyl methacrylate , polymer chemistry , polymer science , polymer , thermodynamics , polymerization , physics
The purpose of this work was to show that physical aging effects in poly(methyl methacrylate) (PMMA) could be correlated with the nonequilibrium state of the glassy polymer, as measured by dilatometry. Specimens were annealed at a series of temperatures within the glass transition region (90, 95 and 100°C) and quenched or slowly cooled to the test temperature (40 or 60°C). Volume recovery was monitored throughout the experiment by accurate dilatometry, and low strain tensile creep compliance measurements were made simultaneously on specimens subjected to identical thermal treatments. At both test temperatures, creep behavior and volume recovery showed a similar dependence on annealing temperature and time. However, the specific volume alone was not sufficient to characterize the aging behavior of glassy PMMA: it was also necessary to define the path by which the state of the glass was reached. This memory effect, which has a direct parallel in volume recovery, is attributed to the presence of a distribution of retardation times, and accounts for, the seemingly paradoxical observation that the creep compliance can initially increase on aging at a temperature below T g if the specimen has previously been stored for a long period at a lower temperature.