Structural studies on polyurethane elastomers obtained with single diisocyanates

1 Structural studies on polyurethane elastomers obtained with single diisocyanates 

A systematic study of PUs with HS of variable crystallinity was made by us [60, 61, 127, 135]. Two diisocyanates were considered the frequently employed MDI, and its close relation DBDI, that is of special interest because of its tendency to crystallize on cooling from the melt in the presence of some chain extenders [135]. The family of model PUs was synthesized for this work in the authors Romanian laboratory. They were all three-component systems combined in stoichiometric proportions, and consisting of (1) a diisocyanate—either MDI or DBDI (2) a SS macrodiol—PEA, PTHF, or PBA and (3) a small molecule diol as chain 

Small-angle X-ray scattering (SAXS) studies were carried out using Daresbury Station 16.1 with the RAPID 2-dimensonal detector, with X-ray wavelength A= 141 pm and a camera length of 4 m. Scattering intensities were radially aver- 

In = + h- Excellent agreement was found in all cases except PUi. For the other 

Secondly, all but two of the scattering patterns obtained showed a distinct peak, at a position q in the region of 0.3 nm . In these cases, a long period d was In 

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