Crystallite orientation during melting of oriented ultra-high-molecular-weight polyethylene |
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Authors: | P Sajkiewicz A Wasiak |
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Institution: | (1) Institute of Fundamental Technological Research, Polish Academy of Sciences Świętokrzyska 21, 00-049 Warsaw Poland e-mail: psajk@ippt.gov.pl Tel.: +48-22-8261281 ext. 148 Fax: +48-22-8269815, PL |
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Abstract: | The changes in crystallite orientation during melting of oriented ultra-high-molecular-weight polyethylene (UHMW PE) were
investigated by means of wide-angle X-ray scattering. The orientation distribution of crystallites in drawn UHMW PE is composed
of two components differing in width. The narrow and broad components revealed in this study indicate the existence of two
classes of crystallites with different orientability. Some of the crystallites are oriented almost perfectly even at low-draw
ratios, while the others do not orient so effectively. The analysis of melting behaviour of such a texture composed of orthorhombic
crystals indicates that highly oriented crystallites are formed by taut molecules and transform first to the hexagonal phase,
while the molecules constituting low-oriented crystallites melt directly to the typical amorphous phase. The increase in orientation
of highly oriented crystallites during their partial melting, observed in the samples kept at constant length and even those
allowed to shrink under constant load, can be explained by the kinetic factor proposed by Ziabicki.
Received: 11 September 1998 Accepted in revised form: 18 February 1999 |
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Keywords: | Oriented polymers Melting Ultra-high-molecular-weight polyethylene |
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