Thermo-mechanical coupling and self-excited oscillation in the neck propagation of PET films

The self-excited oscillation of neck propagation during cold drawing of pol ymer films has been examined experimentally. On the basis of Barenblatt's m odel considering a thermo-mechanical coupling at the neck, the temperature rise at the neck has been studied with an infrared camera. The temperature began to rise in a range showing a negative velocity dependence of the appl ied load. The behavior is consistent with the view of thermo-mechanical cou pling. The temperature rise was up to 80 degreesC (>T-g) and explains the o ccurrence of crystallization for faster drawing rates. It has also been con firmed that the temperature rise follows the oscillation of stress due to t he coupling. (C) 2001 Published by Elsevier Science Ltd.