Structural studies on polyurethane elastomers obtained with mixtures of diisocyanates

2 Structural studies on polyurethane elastomers obtained with mixtures of diisocyanates 

As shown above one of the convenient means to reduce the DBDI based PUs crystallinity was to use the flexible chain extender diethylene glycol (DEG), which inhibits crystallization. But the crystallinity of DBDI based PUs can be also considerably reduced with the incorporation ofMDI as earlier reported [61 ]. 

In the PU synthesis we started from one mole of hydroxy-terminated macro-diol which was either a polyester type—polyethylene adipate (PEA) or a polyether type—polytetrahydrofuran (PTHF). 

For the preparation of the PU elastomer containing simultaneously two different diisocyanates the macrodiol was reacted in different ways with two moles of MDI and two moles of DBDI. Finally the so-obtained different prepolymers were reacted with 2.64 moles of chain extender which was in all the cases ethylene glycol (EG). There were adopted three different modes of prepolymer synthesis leading to three different active PU oligomers. 

PUci Single step prepolymer synthesis which used a melt mixture of the two 

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