Phase Transition during Heating of Nanostructured Ultrahigh Molecular Weight Polyethylene Membranes.
J Phys Chem B
; 119(52): 15909-18, 2015 Dec 31.
Article
em En
| MEDLINE
| ID: mdl-26606251
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.
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01-internacional
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MEDLINE
Idioma:
En
Ano de publicação:
2015
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Article