Dynamics and structure development for biaxial stretching polyamide 6 films

The biaxial stretching film of polyamide 6 (PA6) is widely used for food and industrial products packaging. It is expected to improve stretchability, impact strength, tensile strength, and thermoformability for a larger market. So, in this research, the stretching methods were investigated in terms of dynamics and structure development for the biaxial stretching films. There are three different stretching methods which can produce PA6 films, namely the simultaneous biaxial stretching, the sequential biaxial stretching, and the double bubble tubular process. The physical properties of PA6 film are very much influenced by the biaxial stretching process. But there are no reports which described the difference among the three stretching methods and film properties. For this reason, the higher order structure and stretching behaviors of the three stretching methods were studied. As a result, the sequential biaxial stretching showed strong stretched effect and molecular orientation in the transverse direction (TD) and poor film thickness uniformity, because the strong hydrogen bonds were created during the machine direction (MD) stretching and high stretching stress in the TD stretching was required. In the simultaneous biaxial stretching, the molecular orientation was equal both in the MD and in the TD of the stretched plane. The double bubble tubular process produced well-balanced film and equal orientation in any direction in terms of the phase difference in the plane of film. The biaxially oriented PA6 film having good stretchability and high physical properties was also investigated.