ABSTRACT

As it was already mentioned, the specifi c structural feature of high molecular weight linear PUs, and in particular elastomers, is their segmented structure. The PU chain is composed of hard segments and soft segment arranged alternately [254, 255]. The hard segments are most frequently made of non-polar hydrocarbon structures derived from diisocyanates, urethane oligomers obtained from diisocyanates and lowmolecular weight hydroxyl chain extenders, or urea oligomers produced with the use of diisocyanates and water or amino chain extenders.