Phenomenological theory of structural relaxation based on a thermorheologically complex relaxation time distribution

Andreozzi, L., Faetti, M., Salmerón-Sanchez, M. and Gómez Ribelles, J. L. (2008) Phenomenological theory of structural relaxation based on a thermorheologically complex relaxation time distribution. European Physical Journal E, 27(1), pp. 87-97. (doi:10.1140/epje/i2008-10355-x)

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Abstract

he aim of this work is to explore the consequences on the kinetics of structural relaxation of considering a glass-forming system to consist of a series of small but macroscopic relaxing regions that evolve independently from each other towards equilibrium in the glassy state. The result of this assumption is a thermorheologically complex model. In this approach each relaxing zone has been assumed to follow the Scherer-Hodge model for structural relaxation (with the small modification of taking a linear dependence of configurational heat capacity with temperature). The model thus developed contains four fitting parameters. A least-squares search routine has been used to find the set of model parameters that fit simultaneously four DSC thermograms in PVAc after different thermal histories. The computersimulated curves are compared with those obtained with Scherer-Hodge model and the model proposed by Gómez and Monleón. The evolution of the relaxation times during cooling or heating scans and also during isothermal annealing below the glass transition has been analysed. It has been shown that the relaxation times distribution narrows in the glassy state with respect to equilibrium. Isothermal annealing causes this distribution to broaden during the process to finally attain in equilibrium the shape defined at temperatures above Tg.

Item Type:Articles
Status:Published
Refereed:Yes
Glasgow Author(s) Enlighten ID:Salmeron-Sanchez, Professor Manuel
Authors: Andreozzi, L., Faetti, M., Salmerón-Sanchez, M., and Gómez Ribelles, J. L.
College/School:College of Science and Engineering > School of Engineering > Biomedical Engineering
Journal Name:European Physical Journal E
ISSN:1292-8941
ISSN (Online):1292-895X
Published Online:08 August 2008

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