Structure Evolution and Deformation Behavior of Polyethylene Film during Biaxial Stretching

Abstract

The structure evolution and deformation behavior of tenter-frame biaxially oriented polyethylene (TF-BOPE) films were investigated in this study. For sequential biaxial stretching, the original spherulites were broken into small pieces, and the fibrillar structure simultaneously formed during the machine direction (MD) stretching. Subsequently, the single fibrils were pulled away, and some fine fibrils developed via partial melting–recrystallization or lamellar rearrangement during the transverse direction (TD) stretching, which leads to the formation of the vein structure and nanosized fiber-like network. For simultaneous biaxial stretching, the fractured lamellae and the newly formed crystals were evenly distributed in the MD-TD plane like an isotropous fibrillar network. Moreover, compared with the unstretched sample, both films could achieve up to about 2 times the tensile modulus and 4.5 times the tensile strength and also exhibited the superior optical property.

Transparent semi‐crystalline polymeric materials and their nanocomposites: A review

“…Biaxial orientation can improve physical properties in two perpendicular directions (machine direction, MD F I G U R E 2 A, Appearance of (1) PET preform for stretch-blow molding process, (2) heat-set PET bottle with standard transparent thread and (3) heat-set PET bottle with post-crystallized opaque thread acquired by annealing. [55] B, Transmittance, C, Young's modulus and D, tensile strength of original PE sheets (PE-0), sequentially biaxially stretched (PE-6 × 6) and simultaneously biaxially stretched (PEsim-6 × 6) BOPE films with the draw ratio of 6 × 6 along MD, TD, and diagonal direction (DD) [56] [Color figure can be viewed at wileyonlinelibrary.com] and transverse direction, TD) and enhance the commercial values of polymer films. Some biaxially oriented semicrystalline polymer films stretched in the melt state or the solid state are optically transparent due to the reduced crystal sizes induced during the biaxial stretching process.…”

“…A, Appearance of (1) PET preform for stretch‐blow molding process, (2) heat‐set PET bottle with standard transparent thread and (3) heat‐set PET bottle with post‐crystallized opaque thread acquired by annealing. [ 55 ] B, Transmittance, C, Young's modulus and D, tensile strength of original PE sheets (PE‐0), sequentially biaxially stretched (PE‐6 × 6) and simultaneously biaxially stretched (PE‐sim‐6 × 6) BOPE films with the draw ratio of 6 × 6 along MD, TD, and diagonal direction (DD) [ 56 ] [Color figure can be viewed at wileyonlinelibrary.com]…”

“…These TF‐BOPE films also exhibit better mechanical performance with Young's moduli of around 600 MPa and tensile strengths of 120 MPa in both MD and TD (Figure 2C‐D), such as a twice as high stiffness and dart impact resistance in comparison to conventional blown PE films. [ 56 ] They have been used as the interlayer in liquid detergent bags instead of traditional packaging materials including BOPP, BOPET, and BOPA. In addition, these printable TF‐BOPE films with good color registration can be incorporated with other kinds of PE films to establish fully recyclable and sustainable all‐PE laminates for further packaging applications.…”

The chain microstructure and condensed structure of polyethylene resin used for Biaxially stretched film

“…And the height image of the stretched film appears featherlike feature, corresponding to previous reports. [10,13]…”

“…Evaluations like atomic force microscope (AFM), wide angle X-ray diffraction (WAXD), scanning electron microscope (SEM) and other methods could be used to observe the orientation structure of BOPE film. [8][9][10] Recent studies [11][12][13][14][15] focused on biaxial stretch-induced structural development and deformation behavior of crystals and PE film. During the biaxial stretching process, the lamellar stacks were fractured and converted to a fibrillar structure through melting recrystallization and tilting in the MD-TD plane.…”