Studies of polyurethane elastomers.
Part II. Cast polyurethane elastomers containing biuret and thiobiuret groupings
Two urea derivatives, namely N,N'-ethyleneurea and N,N'- ethylenethiourea, were used in the synthesis of cast polyurethane elastomers. These elastomers were prepared by one of three methods: I — in the bulk, using urea derivative dissolved in 1,4-butanediol; II — in solution in a polar solvent (dimethylsulphoxide or dimethylacetamide); III — in a three-step process comprising preparation of NCO-terminated oligomers, the preliminary extension of this prepolymer with the urea derivative, and the final extension of this system with 1,4-butanediol. The mechanical, thermal and dynamic mechanical properties of the resulting elastomers were investigated by means of a tensile tester and with the use of DSC and DMTA methods. The results supported the conclusion that the used urea derivatives were built into the main chain of elastomer; thus a new group of cast elastomers was obtained:poly(urethane—biurets) and poly(urethane—thiobiurets).
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