Conference paper Open Access
Polyurethane (PU) plastics are widespread in various areas such as adhesives, coatings, synthetic leather, etc. . Frequently, PU plastics are synthesized from two components: 1) macrodiols and 2) isocyanates, whose reactions form urethane linkages . The macrodiol must contain two OH groups with a polyether, polyester, hydrocarbon, polycarbonate or other type of spacer chain in between. Quite often, the macrodiol is pre-reacted with diisocyanates for chain extension and only then cross-linked into the final PU plastic. Resulting properties also depend on molecular weights, degree of crystallinity and morphology of PU polymers  in addition to the consequences of many side reactions, such as CO2 evolution.
Also available on pg 90 of http://www.journals.vu.lt/proceedings/article/view/12830/11636