Volume and Enthalpy Relaxation in Polystyrene

Abstract

A study was carried out on the effects of thermal aging on specific volume V and specific enthalpy H of polystyrene below the glass transition temperature. The dependence of V and H on annealing time was similar. No significant effect of the distribution of molecular weight on the relaxation behavior was found. The behavior of V and H reaching a maximum after a double-step temperature-jump was also investigated. The time for the maximum V and H varied in proportion to the period of pre-annealing. The time for the maximum volume was slightly longer than that for the maximum enthalpy. These facts indicate that the dependence of V and H on the order parameters specifying the glassy state are similar but not exactly the same. From the enthalpy and volume relaxation curves, the enthalpy required for creating free volumes in polystyrene was calculated to be 2.0 kJ cm−3. The behavior of the volume relaxation was discussed by assuming a wide distribution of relaxation time.

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Keywords

  • Volume Relaxation
  • Enthalpy Relaxation
  • Polystyrene
  • Glass Transition
  • Temperature Jump
  • Memory Effect

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