Study of the influence of physical aging on macroradical decay in poly(methyl methacrylate) |
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Authors: | J Barto? M Klimová F Sz?cs |
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Institution: | (1) Polymer Institute of SAS, Dúbrayská cesta 9, 842 36 Bratislava, Slovakia |
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Abstract: | The macroradical decay in poly(methyl methacrylate) samples with different thermal histories was investigated in the temperature interval 20–100 °C using ESR spectroscopy and the second order kinetic model. The rate constants exhibit two different regimes with the transitions atT
tr=68±1°C which are independent of thermal treatment. ForT<T
tr andT>T
tr the rate constants as well as the corresponding activation parameters are sensitive to history because of different physical microstructures. The compensation law, i.e., the linear relation between lnk
o, eff andE
eff, was analyzed in terms of the so-called compensation quantitiesk
c andT
c and a proximity betweenT
c=T
tr andT
o=53±3 °C — Vogel temperature for -segmental dynamics was found. A comparison of kinetic and dynamic data suggests that the decay of terminal macroradicals in the low-temperature region is controlled by secondary relaxations and that the -mobility contributes to a more rapid decay at higher temperatures belowT
g. |
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Keywords: | Physical aging macroradical decay compensation law relaxation dynamics poly(methyl methacrylate) |
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