Eur. Phys. J. E (2014) 37: 63
https://doi.org/10.1140/epje/i2014-14063-8

Regular Article

Study on enthalpy relaxation of glassy polystyrene using a structure-dependent Kohlrausch stretch exponent combined with coupling model

Institute of Polymer Science and Engineering, Hebei University of Technology, 300130, Tianjin, China

^* e-mail: liugd@hebut.edu.cn

Received: 23 December 2013
Revised: 24 March 2014
Accepted: 17 June 2014
Published online: 24 July 2014

Abstract

In this paper the enthalpy relaxation of polystyrene (PS) was restudied using a structure-dependent Kohlrausch stretch exponent β with incorporation of a coupling model (CM). The structure dependence of β is described in 3 semi-phenomenological equations. The temperature and structure dependence of the relaxation time of the Johari-Goldstein (JG) relaxation (τ _JG) is presented using the traditional Tools-Narayanaswamy-Moynihan (TNM) and Adam-Gibbs-Vogel (AGV) equations. The fitting results of heat capacity data are much better than the conventional TNM and Adam-Gibbs (AG) models when the structure dependence of β is described using an exponential equation and τ _JG is calculated using the AGV equation, although there are one fewer fitting parameters in the new model. The results indicate that both the structure dependence of β and the CM model may play considerable roles in the investigation on the structure relaxation process in polymers around the glass transition.