The relation between relaxed enthalpy and volume during physical aging of amorphous polymers and selenium

This paper reports physical aging results for PMMA, PMMA/PEO blends, PS, PC, PVC and PET (semicrystalline). Also included in this study is amorphous selenium. Temperature down-jumps from equilibrium above T(g) to a temperature below T(g) were carried out. Relaxed enthalpy, Delta h and volume contraction, Delta v, were measured. From the aging records, the constant ratio Delta h/Delta v = K(a) was evaluated. For the polymeric samples K(a) values of about 2 GPa were observed, thus similar to the inverse value of the isothermal compressibility close to T(g). Similarly for Se the K(a) value obtained from Delta h and Delta v was in fair agreement with its isothermal compressibility. (c) 2006 Elsevier Ltd. All rights reserved.