TIT# Morphological Failure Mechanisms in Tensile Tests of Crosslinked
     Polyurethanes with Poorly Developed Domain Structure
AUT# Stribeck, Norbert; Li, Xuke; Kogut, Igor; Moritz, Hans-Ulrich;
     Eling, Berend; Goerigk, Gnter Johannes; Hoell, Armin;
SOU# Macromol. Mater. Eng. (2015), 300(7), 699-711
LOC# xv148
CLA#
COM# doi:10.1002/mame.201500007
APP#
MAT#
ABS# Macroscopic failure of polyurethane materials of 30 wt% hard-segment #
     content is related to microstructure evolution mechanisms. Topology and
     functionality (f=2..4) of the polyols are varied. Samples are strained
     and small-angle X-ray scattering (SAXS) patterns are recorded. Only
     material PU-I (f=2) passes the tensile test. Material PU-Hs -- a H-shaped
     (f=4) polyol with short arms -- is not nanostructured. PU-Hl has long
     arms. It contains hard domains placed at random (no mechanical
     interaction). PU-Hl survives longer (strain: 180%) than the other
     short-lived materials. Hard domains are not destroyed. PU-X (f=4,
     star-shaped) develops microfibrils: one-dimensional correlations among
     hard domains, as deduced from a chord distribution function (CDF)
     analysis. PU-I and PU-Y are based on 2- and 3-functional polyols. They
     develop microfibrils, too. Moreover, they exhibit 3D connectivity of
     hard domains seized by tie molecules ("cages"). The arrangement of hard
     domains evolves identically, but not the population density. In PU-I hard
     domains are sacrificed during straining, in PU-Y soft phase appears to be
     extracted from the cages.