Thermoelastic Behaviour of Amorphous Polymers Above and Through the Glass Transition Interval I. Polystyrene |
| |
Authors: | Privalko V P Korskanov V V |
| |
Institution: | (1) Institute of Macromolecular Chemistry, National Academy of Sciences of Ukraine, 253 160 Kyiv, Ukraine |
| |
Abstract: | The thermoelastic behaviour of an unfractionated polystyrene was studied in the temperature interval 353–453 K in the regimes
of isobaric cooling and of isothermal quasi-adiabatic loading, respectively. The main experimental results can be summarized
as follows.
1. In the temperature interval far above the glass transition temperature Tg, both the temperature and volume relaxations of the polystyrene melt after sudden pressure jumps were completely reversible
and proved to be simple exponential functions of the time. Therefore, by a straightforward application of Eqs (1) and (2)
to the relevant thermoelastic data obtained in a single experimental run one can arrive at the reasonable values of the specific
volume, specific heat capacity, thermal diffusivity and heat conductivity of the polymer in the equilibrium melt state.
2. In the temperature interval close to Tg, both the temperature and volume relations of the supercooled polystyrene melt in compression/expansion cycles became markedly
asymmetric and non-exponential. The low values of the exponent β in the fractional-exponent Eq. (5) for the volume relaxation
suggest a broad spectrum of relaxation times indicating the high degree of coupling between different mechanisms of the molecular
motions involved.
This revised version was published online in July 2006 with corrections to the Cover Date. |
| |
Keywords: | glassy state melt state thermal diffusivity thermoelastic effect volume relaxation |
本文献已被 SpringerLink 等数据库收录! |
|