M. Engelhard and A. Lion
In this work a model to describe the behaviour of polymers close to glass transition is presented. The focus lies on the moisture depended properties of polymers. Based on the Coleman & Noll type of evaluation of the Clausius-Duhem inequality a thermomechanically consistent material model is derived, which is based on a series expansion of the Gibbs free energy around thermodynamic equilibrium. Now, besides constraints emanating from the second law of thermodynamics, it is possible to obtain three relations between the stress, the temperature, the internal variables and the water content on the one side and the strain, the entropy and the chemical potential of the water content on the other. Adjusting the free parameters in these relations allows for an accurate reproduction of measuring data from dynamic tension tests with PA 6.