Property Development for Biaxial Drawing of Ethylene-Tetrafluoroehtylene Copolymer Films and Resultant Fractural Behavior Analyzed by in Situ X-ray Measurements

Abstract

The property development of the ethylene-tetrafluoroethylene copolymer (ETFE) membrane induced by simultaneous biaxial drawing was investigated. Commonly, tensile strength can be increased by drawing; conversely, tear resistance decreases. In this study, the balance between tensile strength and tear resistance for the resultant ETFE membrane was optimized achieved by a combination of lamination of low molecular weight (LMW) and high molecular weight (HMW) layers and subsequent biaxial drawing. The structural factor determining tear resistance of these biaxially drawn membranes was determined based on in situ small-angle X-ray scattering (SAXS) measurement during tensile deformation simulating tearing tests. Lozenge shaped scattering, which indicated inclined lamellae, was observed during such tensile deformation of the resultant membranes. Remarkably, this inclined lamellar structure was observed for the pure LMW membrane; however, it also appeared at the interface between LMW and HMW layers within biaxially drawn membranes. For the membrane exhibiting the highest tearing strength, the fraction of such inclined lamella increased up to the critical strain corresponding to the actual sample breaking. These results confirm that the inclined lamellar structure absorbed strain during membrane tearing.

Fluoropolymer microstructure and dynamics: Influence of molecular orientation induced by uniaxial drawing

“…There have been some prior studies on the effect of drawing and chain orientation on ETFE films. [22][23][24][25] Films at high extension adopt an oriented herringbone-type arrangement of crystal lamellae. 22,25 Film extension and orientation has also been suggested to induce formation of an extended-chain conformation.…”

“…23 Biaxial orientation has also been investigated. 24 However there has been no discussion on how the oriented lamellar morphology develops in ETFE as extension is increased, and how this affects the segmental dynamics. Many studies have been carried out to determine the unit cell structure of crystalline ETFE.…”

An Extensive Review on the Viscoelastic-plastic and Fractural Mechanical Behaviour of ETFE Membranes

“…This might result from the molecular properties of the foils, as detailed previously, but the manufacturer did not provide these properties for the resin. Uehara et al (2015) investigated the tensile strength and tear resistance of ETFE membranes in terms of molecular crystalline alignment. In their study, they made biaxial tensile measurements with a small-angle X-ray scattering method on laminates consisting of low and high molecular weighted ETFE membrane layers.…”

Nanoporous Membranes Prepared from Homogeneous Lamellar Structure Developed via Biaxial Melt‐Drawing of Ultra‐High Molecular Weight Polyethylene/Normal Molecular Weight Polyethylene Blend Films

“…[ 14,15,17 ] A similar high performance membranes is obtained by biaxial drawing for the poly(tetrafluoroethylene) [ 17,18 ] and ethylene‐tetrafluoroethlene copolymer. [ 17,19 ] Our recent study also clarified that blending normal molecular weight polyethylene (NMW‐PE) with UHMW‐PE induces the homogeneous lamellae structure by uniaxial melt‐drawing, [ 20 ] meaning that the melt‐shrinking process necessary for pure UHMW‐PE can be skipped, which is advantageous for industrial applications. Therefore, the above uniaxial melt‐drawing of UHMW‐PE/NMW‐PE blend film is extended to biaxial melt‐drawing in this study to prepare the membranes composed of a nano‐network structure consisting of homogeneous FCCs over a large area.…”