“…There are typically two types of stretching methods used to create such films: inflation molding, in which films are blown in a tubular shape, and tenter molding, in which films are elongated in the machine direction and/or the transverse direction by tenter clips [2,3]. Thus, oriented iPP films can be produced by a variety of stretching techniques based on sequential as well as simultaneous drawing processes using various balanced draw ratios at high temperatures near the melting point and at extremely high elongation speeds [4]. Elucidation of the deformation mechanism under biaxial stretching on the molecular scale would undoubtedly be indispensable for designing and controlling various physical properties of biaxially oriented iPP films.…”