title: Phase Transition during Heating of Nanostructured Ultrahigh Molecular Weight Polyethylene Membranes.
abstract: Ultrahigh molecular weight polyethylene (UHMW-PE) membranes were prepared using biaxial melt-drawing and subsequent melt-shrinking. Electron microscopy observations indicate that the former membrane has more extended-chain crystals (ECCs), whereas the latter is mainly composed of folded-chain crystals (FCCs). Corresponding double-melting endotherms are recorded on differential scanning calorimetry (DSC) measurements. Detailed assignments of such double-melting components are performed using in situ X-ray measurements during heating. Wide- and small-angle X-ray diffraction and scattering (WAXD/SAXS) images were simultaneously recorded at SPring-8. Changes in WAXD images indicate that the orthorhombic reflection peak begins to decrease at 130 °C, followed by the appearance of the hexagonal reflection peak beyond 145 °C for both membranes, but the latter melt-shrunk membrane exhibits weaker hexagonal reflection intensity. Simultaneous SAXS results indicate that FCCs rapidly disappear at 135 °C for the melt-shrunk membrane, resulting in a sharper endotherm. In contrast, residual ECCs restrict the melting of FCCs for the melt-drawn membrane, resulting in a broader endotherm of FCC melting spread to a slightly higher temperature position.
authors.affiliation: Division of Molecular Science, Faculty of Science and Technology, Gunma University , Kiryu, Gunma 376-8515, Japan.
authors.forename: Hiroki
authors.initials: H
authors.lastname: Uehara
authors.affiliation: Division of Molecular Science, Faculty of Science and Technology, Gunma University , Kiryu, Gunma 376-8515, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Tamura
authors.affiliation: Division of Molecular Science, Faculty of Science and Technology, Gunma University , Kiryu, Gunma 376-8515, Japan.
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Yamashita
authors.affiliation: Division of Molecular Science, Faculty of Science and Technology, Gunma University , Kiryu, Gunma 376-8515, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Yamanobe
authors.affiliation: Japan Synchrotron Radiation Research Institute (JASRI/SPring-8) , Kouto 1-1-1, Sayo-cho, Sayo-gun, Hyogo 679-5148, Japan.
authors.forename: Hiroyasu
authors.initials: H
authors.lastname: Masunaga