TIT# Structure transfer between a polymer melt and the solid state. Investigation
     of the nanostructure evolution in oriented polyethylene by means of continuous
     X-Ray scattering
AUT# Stribeck, Norbert; Bösecke, Peter; Bayer, Rüdiger; Almendarez Camarillo, Armando;
SOU# Progr. Coll. Polym. Sci. (2005), in print
LOC# xv089 @ PCPSru02sub.pdf
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ABS# During the melting and crystallization of uniaxially
     oriented polyethylene small-angle X-ray scattering
     (SAXS) and wide-angle X-ray scattering (WAXS) patterns
     are recorded simultaneously and continuously, i.e. with
     high signal-to-noise ratio and a time resolution of 7 s.
     The multidimensional chord distribution function (CDF)
     is computed from each of the SAXS patterns and
     visualises the nanodomain structure of the material in
     physical space. Thus without application of a model a
     detailed and continuous multidimensional stream of data
     is obtained that reveals the mechanisms which govern
     melting and crystallization in the material studied.
     Finally the CDF is semi-quantitatively analysed as a
     function of the temperature programme.
     We find that swarms of small crystalline blocks which
     are observed during the heating of the injection
     moulded rods are melting earlier than the extended
     lamellae. Directly after the last lamellae have
     vanished we quench to a crystallization temperature. No
     formation of blocky crystals is observed. Instead,
     before the beginning of crystallization, a mesophase
     separation into disentangled and entangled regions is
     indicated. Moreover, row structures of nuclei are
     observed coming and going. As long as these rows are
     oriented in fibre direction, the orientational memory
     of the melt is not erased. Crystallization starts in
     disentangled bundles of chain segments at the tips of
     knots (entanglement strands). Fast and continuous
     lamellar growth is observed. Most of the lamellae are
     positioned at random. Correlations between lamellae are
     limited to twins which are formed when lamellae grow at
     both ends of the same entanglement strand. Thereafter
     slow thickness growth of lamellae is observed, and in
     twins this growth is directed outwardly, away from the
     entanglement-rich amorphous zone between them. Only
     during this period the wide-angle X-ray scattering
     (WAXS) exhibits an increasing orientation of the
     crystals. At a high undercooling or after there is no
     space for lamellae any more, secondary crystals
     (blocks) are formed that are unoriented but placed in
     such a manner that correlations among them are high
     both in longitudinal and transversal direction.