Photodegradation of Segmented Polyurethanes Based on Aromatic Diisocyanates.
UNIVERSITY OF SOUTHERN MISSISSIPPI HATTIESBURG DEPT OF POLYMER SCIENCE
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The photodegradation of polyurethane based on aromatic diisocyanates is shown to be dependent on the physical state of the polymer. For simple polyurethane based on p,p-diphenylmethane diisocyanate MDI and a single diol, films with low crystallinity and high flexibility degrade quite rapidly upon exposure to UV radiation. In the case of segmented polyurethanes based on MDI and more than one diol, the extent and mechanism of photolytic decomposition is dependent on the hard segment MDI-1,4-butanediol content in the polymer. As the degree of hard segments in the polymer increases both the percent crosslinked gel and discoloration generated upon photolysis decreases dramatically. In addition, formation of the ortho photo-Fries rearrangement product increases with an increase in the molecular weight of the polyethylene oxide soft segment.
- Radiation and Nuclear Chemistry