Polyurethane Incompatible polyols

Polyurethane (PU) materials have been formed by RIM using a commercial isocyanate reacting with either various compatible or incompatible polyol blends, or with slurries containing polyol blends and glass fibres. 

A one-part, heat-curing polyurethane adhesive has recently been introduced in which the curative is incompatible, and hence nonreactive, with an isocyanate prepolymer. Upon heating, the finely dispersed polyol curative becomes reactive towards the prepolymer and curing takes place. 

PUs can be both thermoplastic and thermosetting materials composed by HS and SS. Thermoplastic polyurethanes (TPU) are formed by linear polymer chains with functionality equal to two. This means that the SS, the polyol, is a diol and the HS, the isocyanate, is a diisocyanate. The thermodynamic incompatibility between the hard and the SSs as well as the NCO OH ratio, the synthesis procedure, etc. can generate a phase separation into the TPU. On the other hand, the thermosetting PUs are formed by polyols and/or isocyanates with functionalities higher than 2, with a NCO OH ratio higher than 1 or are obtained by using cross-linker agents. 

---