Beitrag zur bestimmung von hydroxylzahlen in ungesättigten polyesterharzen

Some methods for determining the hydroxyl number were tested for their applicability to unsaturated polyester resins. The p-toluenesulfonic acid catalyzed acetylation in ethyl acetate was found to be a generally applicable procedure for quick and easy determinations. Acetylation in pyridine requires longer reaction times. The end point of the subsequent titration of acetic acid is hard to recognize, thus giving uncertain results. The reaction time of acetic anhydride for each resin has to be carefully determined when perchloric acid is used as acetylation catalvst.