Urethane-forming ingredients

The urethane forming ingredients in a polyurethane foam formulation are the isocyanate (1) and the polyol (2) as shown in equation 3. 

Supercritical fractionation was investigated for the special-purpose polymers of both the diol and triol of a glycidyl azide polymer and a hydroxy-terminated polybutadiene. Hydroxy polybutadiene is used on a large scale as an ingredient in plastic bonded explosive (PBX) propellant formulations the hydroxy functionality of the polybutadiene reacts with an isocyanate functionality of another prepolymer to form a urethane. In the polysiloxanes section we referred to functionally terminated polymers as macromonomers in the terminology of the urethane industry, however, isocyanate-terminated polyester polymers are normally referred to as prepolymers in their reaction to form the urethane, even though the prepolymers are typically between 1,000 and 10,000 molecular weight. 

Reactive acrylics are differentiated from other two-component adhesive systems snch as epoxies or urethanes by the fact that the cure is catalytic, is relatively insensitive to the amount of catalyst used, and is not dependent npon mixing precise stoichiometric amounts of adhesive and catalyst. An important development was the commercialisation of a highly pnrified form of dihydropyridine activator which contains 85-90% of the key active ingredient 3,5-diethyl-l,2-dihydro-l-phenyl-2-propylpyridine ... 

The usual ingredients for forming urethane polymers are a silicone surfactant (sometimes called releasing agent), a flame retardant, a polyol, a diisocyanate, and a suitable catalyst. Polyols used have alcoholic functional groups and are rarely small molecules like ethylene glycol. The formation of the polymer is usually fast, even without catalysts, but recent applications snch as reaction injection molding (RIM) require very fast reactions for which a catalyst... 

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