Investigation on the rheological behavior of PA6 film during biaxial stretching

Abstract

In this work, the rheological behavior of polyamide 6 (PA6) film during biaxial stretching was investigated. Firstly, the cast film was subjected to different ratios of biaxial stretching, and the stress calculation expression of biaxial stretching was derived. Then the generalized Maxwell model was employed to fit the stress-time curves in the heat setting stage. It was found that the elastic-plastic deformation during biaxial stretching influenced the stress rebound or relaxation in the heat setting. Finally, the relaxation spectrum and activation energy spectrum were calculated according to the fitting curves. It was found that the stress relaxation process of PA6 film was divided into multiple stages, but the stress rebound process was relatively simple. According to the activation energy spectrum, we speculated that stress relaxation was a process of releasing energy, and stress rebound was a process of absorbing energy. With the increased stretching ratio, the peaks on the activation energy spectrum became sharper and the intensity increased. Indicating that more energy was released or absorbed under the larger stretching ratio. The obtained results would provide theoretical guidance for further understanding the biaxial stretching deformation mechanism of polymer films.