The instant invention is directed to polyurethane plastics which may be cellular, produced by reaction of polyisocyanates with relatively high molecular weight polyhydroxyl compounds and, optionally, low molecular weight polyhydroxyl compounds, and diamines, said polyurethane plastic containing structural units corresponding to the general formula ##STR1## in which R' represents a straight or branched divalent aliphatic, cycloaliphatic or aromatic radicals containing from 2 to 20 carbon atoms andR" represents hydrogen, a straight or branched alkyl radical containing from 1 to 6 carbon atoms, an aryl radical containing from 6 to 15 carbon atoms, a cycloalkyl radical containing from 4 to 12 carbon atoms, halogen, --NO.sub.2, --CN, --OR'" or a radical ##STR2## where R"' represents a straight or branched alkyl radical containing from 1 to 6 carbon atoms.