TIT# Nanostructure of atmospheric and high-pressure crystallized
     poly(ethylene-2,6-naphthalate). Part II: structure-microhardness correlations
AUT# García Gutiérrez, M. C.; Rueda, D. R.; Baltá Calleja, F. J.; Stribeck, N.;
     Bayer, R. K.;
SOU# Polymer (2003), 44(2), 451-455
LOC# xv077 @ selbst/xv077.pdf
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COM#
APP#
MAT#
ABS# The microhardness of poly(ethylene naphthalene-2,6-dicarboxylate)
     (PEN), with a detailed characterized nanostructure has been investigated.
     PEN samples were crystallized from the glassy state at atmospheric
     pressure and from the melt at high pressure and were characterized using
     small-angle X-ray scattering (SAXS), wide-angle X-ray scattering (WAXS)
     and differential scanning calorimetry (DSC). Results show that the degree
     of crystallinity derived from WAXS, for both atmospheric and
     high-pressure crystallized PEN, is smaller than that obtained by density
     and calorimetry. For high-pressure crystallized samples, both,
     crystallinity and microhardness values are larger than those found for
     the material crystallized under atmospheric pressure. In the latter case,
     the hardness values depend on the volume fraction of lamellar stacks
     within spherulites $X_L$ that depends on the crystallization temperature
     $T_c$. For $T_c$ < 200 °C, $X_L$ is found to be less than 50%. Thus, for
     $T_c$ < 200 °C a linear relationship between H and $T_c$ is observed
     provided a sufficiently long crystallization time is used. Results are
     discussed in terms of the rigid amorphous fraction that appears as a
     consequence of the molecular mobility restrictions due to the crystal
     stacks.