二層 COP/LLDPE フィルムの一軸・二軸延伸挙動における高次構造形成

抄録

This paper reports on an experimental study on the higher-order structural forming of bi-layer film in the process of uni-axial/bi-axial stretching. Bi-layer films produced by co-extrusion of cycloolefin polymer (COP) and linear low-density polyethylene (LLDPE) were stretched using a film stretcher equipped with a high-speed camera to investigate the effect of the interface of each layer. While the stretching conditions for successful stretching of each layer were different, we observed several behaviours during stretching that were not obtained for mono-layer films. In uniaxial stretching of COP/LLDPE film, when the COP layer was stretched beyond its limit, it produced a whitening appearance. In biaxial stretching, the LLDPE layer was successfully stretched at 80 ℃, showing void generation in the COP layer beyond the stretching limit, thereby improving the stretching ratio. The void-generation phenomenon in bi-axial stretching showed dependence on the stretching speed. When stretched at a speed of 0.1m/min, void generation was not significantly observed, maintaining a transparent appearance. As the stretching speed was increased from 1 to 5m/min, the void-generating point shifted to a lower draw ratio during stretching. A tensile test was applied to evaluate the mechanical properties of COP/LLDPE stretched film and the contributions from each layer. Differential scanning calorimetry, transmission electron microscopy, and wide-angle X-ray diffraction were used to evaluate the higher-order structure of the COP/LLDPE film.