Effect of Glycols as Chain Extenders on the Cross-Linking Density of Microcellular Urethane Elastomers

Results are presented from an investigation of the effect of the quantity of ethanediol, 1,6-hexanediol and 1,10-decanediol, applied as microcellular chain extenders, as well as the effect of the NCO-to-OH molar ratio, on changes in the cross-linking state caused by primary and secondary bonds in microcellular elastomers. The urethane elastomers tested were prepared by the two-stage method from the Mipolur-type quasiprepolymer and polyol mixtures having varying quantities of exchangeable glycols. Also demonstrated was the differential effect of the glycols tested on changes in cross-linking by primary and secondary bonds, and changes in cross-linking density as a function of their quantity were found for ethanediol and 1,6-hexanediol. A continuous increase in the quantity of primary and secondary bonds as a function of the quantity of 1,10-decanediol was found. A change of the NCO-to-OH molar ratio within 1,10 to 1,6 gave an extreme case of the change of the cross-linking state by primary and secondary bonds, and whatever the glycol tested, the maxima appear at an NCO-to-OH molar ratio of 12 to 13.