Theoretical approach to the temperature dependence of local flow in polymer systems

Abstract

Starting with the concept of temperature dependent apparent activation energy of flow as a specific temperature function of the considered polymer system a general appraoch is presented, which includes both the Arrhenius and the WLF behaviour. It is demonstrated how local flow can be characterized directly from mechanical measurements via temperature dependent apparent activation energy of flow, using two parameters only, the apparent activation energy of flow extrapolated to infinite temperature, and the Vogel temperature as obtained by extrapolation to infinite activation energy. Examples are given in order to confirm the usefullness of these parameters for molecular interpretation of changes in the local flow mechanism as well as for clarification of the dependences between the polymer structure and the local flow process. As an unique effect it has been found that the energetic interaction of oligomeric polystyrene with poly(vinylmethylether) is much more pronounced than that with high molecular weight polystyrene. This findings may exhibit technical relevance.