The crystalline hard segment models of segmented polyurethane elastomers are made of 4,4'-diphenylmethane diisocyanate (MDI) and 1,4-butanediol (BD). Here we investigate the crystalline behavior of polyurethane that in addition contain 1,1,1-trimethylol propane (TMP), poly(oxytetramethylene) glycol (PTMG), and polyethylene glycol (PEG). The melting points (Tm) of crystallized MDI-BD units decreased with increasing TMP contents and increased with increasing PTMG contents, respectively. A decrease in molecular weight of PTMG and incorporation of PEG decreased Tm. These results indicate that incorporation of a third component would cause to form the well-ordered crystal being closed to equilibrium state.
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