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SMALL-ANGLE X-RAY-SCATTERING OF SEGMENTED BLOCK COPOLYETHERESTERS DURING STRETCHING

1994    STRIBECK, N; APOSTOLOV, AA; ZACHMANN, HG; FAKIROV, C; STAMM, M; FAKIROV, S

The scattering behaviour of polyetherester thermoplastic elastomers based on polybutylene terephthalate as hard segments and polyethylene glycol (MBAR(n) = 1000) as soft segments in a ratio 49/51 wt.% is studied under stress. Drawn (lambda = 5) bristles are annealed with fixed ends in order to create a standard initial structure. Samples with structure destroyed by additional drawing as well as with structure regenerated by solid-state reactions or chemical crosslinking are prepared. The data from small-angle x-ray scattering (SAXS) taken under or without stress are evaluated using Stribeck's method and the sizes of crystalline (dBAR1) and amorphous (dBAR2) regions are directly obtained. A constant value of dBAR1 almost-equal-to 50 angstrom is found for all samples except for the chemically crosslinked one, for which dBAR1 changes at deformations higher than 80% due to axial displacement of the crystallites. The size of the amorphous regions dBAR2 measured under stress (is-an-element-of > 30-50%) rises slightly and reversibly followed by a drop similarly to the measurements without stress, thus indicating that the observed changes in the LBAR-value are due to changes in the amorphous regions only. Further, in the chemically crosslinked sample a reversible axial displacement of the crystallites is observed in the range is-an-element-of = 100-200%, suggesting a complete elimination of the interfibrillar contacts as well as stretching and relaxation of intrafibrillar tie molecules.