Enthalpy recovery: Do materials reach the equilibrium LINE?

Qingxiu Li, Sindee L. Simon

Research output: Contribution to conferencePaperpeer-review


Glasses are inherently non-equilibrium materials, and consequently, their properties evolve toward equilibrium in a process known as structural recovery or physical aging. Recently, several authors have suggested that the equilibrium liquid line is not reached even when properties have ceased to evolve. In this work, we present measurements of the enthalpy recovery of polystyrene at temperatures ranging from the vicinity of glass transition temperature to 10°C below T g (90°C), for aging times up to 200 days. The results are analyzed in the context of the TNM model of structural recovery. In addition, we analyze data in the literature to determine whether enthalpy recovery ceases prior to the material reaching the equilibrium liquid line obtained by extrapolation of the liquid line above T g. The results suggest that, in fact, the liquid enthalpy line is reached at temperatures below T g when equilibrium is reached, i.e., when properties cease to evolve.

Original languageEnglish
Number of pages5
StatePublished - 2006
EventSociety of Plastics Engineers Annual Technical Conference 2006, ANTEC 2006 - Charlotte, NC, United States
Duration: May 7 2006May 11 2006


ConferenceSociety of Plastics Engineers Annual Technical Conference 2006, ANTEC 2006
Country/TerritoryUnited States
CityCharlotte, NC


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