A Comparison of Volume Recovery and Physical Aging Using Simultaneous Measurements in the NIST Torsional Dilatometer
Carl R. Schultesiz, G B. McKenna
At temperatures below the glass transition, amorphous polymers evolve slowly toward thermodynamic equilibrium. Some experiments have suggested that different material properties equilibrate a different rates, but such comparisons are typically made using different samples in different instruments, leading to questions about the comparability between the materials or thermal histories. Using the NIST Torsional Dilatometer [Duran and McKenna, Journal of Rheology, 34, 813-839, 1990], simultaneous measurements of volume (a measure of the thermodynamic state) and mechanical response (using torsional stress-relaxation experiments) can be made on the same sample. Contrary to some prior results from this laboratory [Santore, et al., Polymer, Vol.32, 2377-2381, (1991); McKenna, et al., Polym. Eng. Sci., Vol. 35, 403-410, (1995); McKenna, et al., in Deformation, Yield and Fracture of Polymers, Proc. 9th Int. Conf., Cambridge, UK, 31/1, (1994).], here we report new measurements on an epoxy that indicate that the volume and mechanical properties equilibrate at the same time. The epoxy sample has also exhibited significant chemical aging, as manifested by increasing relaxation times, over the (2 year) course of experiments at the same temperature.
and McKenna, G.
A Comparison of Volume Recovery and Physical Aging Using Simultaneous Measurements in the NIST Torsional Dilatometer, Journal of Rheology
(Accessed December 10, 2023)