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The yield behavior of PVDF and the deformation process at high temperature

par Hellinckx, Sandrine ;Bauwens, Jean Claude
Référence Colloid and polymer science, 273, 3, page (219-226)
Publication Publié, 1995-03

Article révisé par les pairs

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Résumé :

Tensile yield stress measurement on polyvinylidene fluoride are presented covering as many as seven decades of strain-rates at temperatures from -50° to 150°C. The data have been analyzed on the basis of four Ree-Eyring processes acting in parallel, three of which have been identified. At high temperatures and low strain-rates, a threshold yield stress is observed. A model is proposed, allowing to describe the yield behavior both at the threshold and in its adjacent strain-rate dependent range. It consists in a modification of the Ree-Eyring theory using an unsymmetrical free energy barrier for the rate process. The data are fully consistent with the above model which implies that yielding occurs only when the stress is higher than a threshold. In this case, a rejuvenation (or de-aging) effect must be assumed in the deformation process which could consist in a melting of a chain segment located between two folds. © 1995 Steinkopff Verlag.