Small Angle X-Ray Scattering of Segmented Block Copolyetheresters during Stretching

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Abstract
The scattering behaviour of polyetherester thermoplastic elastomers based on polybutylene terephthalate as hard segments and polyethylene glycol ( Mn = 1000) as soft segments in a ratio 49/51 wt.% is studied under stress. Drawn (λ = 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 (d 1) and amorphous (d 2) regions are directly obtained. A constant value of d 1 ≊ 50 Å is found for all samples except for the chemically crosslinked one, for which d 1 changes at deformations higher than 80% due to axial displacement of the crystallites. The size of the amorphous regions d 2 measured under stress (ε > 30-50%) rises slightly and reversibly followed by a drop similarly to the measurements without stress, thus indicating that the observed changes in the L -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 ε = 100-200%, suggesting a complete elimination of the interfibrillar contacts as well as stretching and relaxation of intrafibrillar tie molecules.