Acid Catalysis and Prepolymer Stability Shelf Life

Acid Catalysis and Prepolymer Stability (Shelf Life) 

Acids influence the NCO/OH reaction by accelerating chain extension a little, and retarding crosslinking. If p-nitrobenzoylchloride is added to a urethane system in which active hydrogen compounds must be present, this additive has a mild catalytic effect on chain extension, no effect on allophanate formation, and a strong retarding effect on biuret formation. If water is present the reaction is strongly catalyzed. 

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