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

The scattering behaviour of polyetherester thermoplastic elastomers ba sed on polybutylene terephthalate as hard segments and polyethylene gl ycol (MBAR(n) = 1000) as soft segments in a ratio 49/51 wt.% is studie d under stress. Drawn (lambda = 5) bristles are annealed with fixed en ds in order to create a standard initial structure. Samples with struc ture destroyed by additional drawing as well as with structure regener ated by solid-state reactions or chemical crosslinking are prepared. T he data from small-angle x-ray scattering (SAXS) taken under or withou t stress are evaluated using Stribeck's method and the sizes of crysta lline (dBAR1) and amorphous (dBAR2) regions are directly obtained. A c onstant value of dBAR1 almost-equal-to 50 angstrom is found for all sa mples except for the chemically crosslinked one, for which dBAR1 chang es at deformations higher than 80% due to axial displacement of the cr ystallites. The size of the amorphous regions dBAR2 measured under str ess (is-an-element-of > 30-50%) rises slightly and reversibly followed by a drop similarly to the measurements without stress, thus indicati ng that the observed changes in the LBAR-value are due to changes in t he amorphous regions only. Further, in the chemically crosslinked samp le a reversible axial displacement of the crystallites is observed in the range is-an-element-of = 100-200%, suggesting a complete eliminati on of the interfibrillar contacts as well as stretching and relaxation of intrafibrillar tie molecules.