Investigation of the Photolysis of Polyurethanes Based on 4-4'-Methylene Bis(Phenyldiisocyanate) (MDI) Using Laser Flash Photolysis and Model Compounds.

摘要

Mechanistic evidence is given for the primary pathways leading to the photochemistry of aromatic diisocyanate based polyurethanes. Laser flash photolysis studies on 4,4'-methylene bis(phenyldiisocyanate) (MDI) based polyurethanes and appropriate model compound analogs are presented. Transient species are produced by both direct photolysis (248 nanometers) and indirect photolysis (351 nm) via tert-butyl peroxy radicals in solution. The results provide strong evidence supporting a dual mechanism for photodegradation involving both hydrogen peroxide formation and photo-Fries rearrangement. Keywords: Reprints, Polymers, Photolysis, Decomposition, Urethanes, Carbamates, MDI, Cyanates, Esters, Laser flash photolysis. (jg)