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SynopsisThe effect of the polymerization method (one-or two-stage) on the morphology and properties of specific polyether-and polyester-based urethanes was studied. For the systems investigated, the polymerization technique was somewhat more influential on properties when the soft segment was a polyester than when it was a polyether. In the case of the polyester, a onestage process yields materials with somewhat poorer physical properties than for a two-stage technique. This decrease in properties is attributed to a higher soft-hard segment interaction and to the higher mutual solubility of the segments that is brought about by a possible broader molecular weight distribution of hard segments produced in a one-stage reaction. A large difference in hard segment length distribution, however, was not expected since the MDI isocyanate moieties should display equal reactivity. In the case of polyether soft segments, any effect of the polymerization method appears to be largely offset by the higher incompatibility of the hard and soft components.

CP 65 d 0.221 DEP CP 86 d0 CB stands for chlorinated biphenyl and DEP for diethyl phthalate. 6 CP stands for the method using a cone-and-plate type relaxometer and TT the method utilizing the tensile tester as explained in text. c Present study. d Reference 4.

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