TIT# Nanostructure and mechanical properties studied during dynamical
     straining of microfibrillar reinforced HDPE/PA blends
AUT# Denchev, Zlatan; Dencheva, Nadya; Funari, Sérgio S.;
     Motovilin, Mladen; Schubert, Tom; Stribeck, Norbert;
SOU# J. Polym. Sci. Part B: Polym. Phys. (2009), submitted
LOC# xv121
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ABS# Oriented polymer blends based on high-density polyethylene (HDPE)
     are strained until failure. Two-dimensional (2D) small-angle
     X-ray scattering patterns monitor the nanostructure evolution.
     Data evaluation methods for high-precision determination of
     macroscopic mechanical and nanoscopic structure parameters are
     presented. The hardest materials exhibit a very inhomogeneous
     nanodomain structure. During straining their domains appear to be
     wedged together and inhibit transverse contraction on the
     nanometer scale.
     Further components are polyamides (PA6, PA12) (20--30%) and as
     compatibilizer Yparex 8102 (YP) (0--10%). Some HDPE/PA6 blends
     are additionally loaded with nanoclays (Nanomer or Cloisite).
     Blending of HDPE with PA12 causes no synergistic effect. In the
     absence of nanoclay, PA6 and HDPE form a heterogeneous
     nanostructure with high Young's modulus. After addition of YP a
     more homogeneous scaffold structure is observed in which some of
     the PA6 microfibrils and HDPE crystallites appear to be rigidly
     connected, but the modulus has decreased. Both kinds of nanoclay
     induce a transition from a structure without transverse
     correlation among the microfibrils into a macrolattice with 3D
     correlations among HDPE domains from neighboring microfibrils.
     For extensions between 0.7% and 3.5% the scattering entities with
     3D correlation exhibit transverse elongation instead of
     transverse contraction. The process is interpreted as overcoming
     a correlation barrier executed by the crystallites in an
     evasion-upon-approaching mechanism. During continued straining
     the 3D correlation is reduced or removed.