I have made polyurethanes from methylene diphenyl diisocyanate (MDI). There is no moisture in the reaction. The final polymer is faint yellow or brown even when I used a sterically hindered phenolic antioxidant namely, Irganox 1098. The color of the polymer intensifies after heating the polymer at 160-170 deg C under pressure. The polymer is otherwise stable at that temp. The degradation temperature is higher than 170 deg C. Can you suggest anything to eliminate the color of the polymer both after synthesis and molding? Thanks
Do column chromatography .Disolve the compound in suitable solvent pair (Ethyl acetate :hexane most of the time) & pass the compound through silica column collect fractions . distill out pure fractions to get colour free compound.this is general technique to get pure compounds .
Thanks Nitin for the answer. But do you suggest column chromatography for the polymer?
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