Aging bulk modulus obtained from enthalpy and volume relaxations of a-PMMA and its blends with PEO |
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| Authors: | Petr Slobodian Juliette Vernel Vladimír Pelíšek Petr Sáha Pavel Říha Rodney W. Rychwalski Josef Kubát Igor Emri |
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| Affiliation: | (1) Faculty of Technology, Tomas Bata University in Zlín, Polymer Centre, Prague, Czech Republic;(2) Department of Materials Science and Engineering, Chalmers University of Technology, Gothenburg, Sweden;(3) Institute of Hydrodynamics, Academy of Sciences of the Czech Republic, Prague, Czech Republic;(4) University of Ljubljana, Center for Experimental Mechanics, Ljubljana, Slovenia |
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| Abstract: | Enthalpy and volume relaxation data measured on atactic poly(methyl methacrylate) and its blends with poly(ethylene oxide) are used to calculate an aging bulk modulus, K
a
, tentatively defined as the derivative (∂ h∂ v)
T
. The K
a
values are mainly lower than the corresponding bulk modulus data determined directly with a piston-type PVT-device. On the whole, however, the K
a
values can be considered as lying close to the moduli measured in the liquid state. This notion is supported by K
a
data measured on amorphous selenium, which has a significantly lower compressibility in the liquid state than common amorphous polymers. The results are discussed in terms of thermodynamics of irreversible processes using a single internal variable, yet without arriving at suitable expression for the enthalpy/volume derivative. |
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| Keywords: | Enthalpy and volume relaxation Bulk modulus Compressibility Thermal properties Internal parameter |
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