TIT# Deformation Behavior of Poly(ether ester) Copolymer As Revealed by
     Small- and Wide-Angle Scattering of X-ray Radiation from Synchrotron
AUT# Stribeck, N.; Sapoundjieva, D.; Denchev, Z.; Apostolov, A. A.;
     Zachmann, H. G.; Stamm, M.; Fakirov, S.
SOU# Macromolecules (1997), 30(5), 1329-1339
LOC# xv027  @selbst.ftx
CLA#
COM#
APP#
MAT#
ABS# The deformation behavior of poly(ether ester) is studied by means of
     small- and wide-angle X-ray scattering (SAXS and WAXS).
     The material under investigation represents a polyblock
     thermoplastic elastomer of poly(ether ester) (PEE) type.  It
     comprises poly(butylene terephthalate) (PBT) as hard segments and
     polyethylene glycol (PEG) as soft segments in a ratio of 57/43 wt %.
     Isotropic PEE bristles are drawn to five times of their initial
     length and subsequently annealed with fixed ends for 6 h at 170
     °C in vacuum.  The WAXS patterns were registered by a pinhole
     camera and a 2D area gas detector.  These measurements were
     performed both under stress and during the subsequent relaxation in
     the absence of stress.  The deformation was increased stepwise up to
     the breaking point of the sample (ca. 185%).  SAXS
     patterns were obtained in the same deformation range by means of
     monochromatic X-ray radiation in the beamline A2 of the synchrotron
     DESY in Hamburg, Germany.  SAXS patterns were registered
     by means of a 2D "Image-plate" detector.  Five deformation intervals
     were revealed by SAXS.  In the first one ($\epsilon$ =
     0-50%) an ensemble of uncorrelated strained microfibrils exists and
     the corresponding layer line small-angle pattern is observed  These
     microfibrils scatter independently.  In the second interval
     ($\epsilon$ = 50-80%) interactions between neighboring microfibrils
     develop, a microfibrillar network is observed, and the layer line
     pattern transforms into a four-point diagram.  In the third interval
     ($\epsilon$ = 80-100%) two additional reflections show up and an unique
     six-point pattern is seen.  Pull-out of tie molecules from crystallites
     begins to fibrillate the network.  This pull-out mechanism is
     independently proved by WAXS.  In the fourth interval ($\epsilon$ =
     100-130%) the mean long period of the four-point pattern decreases
     and the pattern itself vanishes.  At last the fiber is completely
     fibrillated and only a two-point pattern remains visible.  In the
     second, third, and fourth intervals, the microfibrils correlate in
     the transverse direction, which allows determination of the interfibrillar
     distance (so-called transverse long period).  It decreases gradually
     with the progress of deformation in both the strained and relaxed
     state.  In the fifth interval ($\epsilon$ > 130%) the long period of
     the two point pattern remains constant, but its intensity decreases
     until the fiber breaks.  Only a few microfibrils are simultaneously
     carrying the load.  They are destroyed one by one, until the fiber
     breaks as a whole.