GB/T 31412-2015 "Binders for paints and varnishes - Determination of hydroxyl value - Titrimetric method" is applicable to the determination of hydroxyl value in binders for paints and varnishes. After the sample is treated with specific reagents, phenolphthalein is used as an indicator, and a standard titration solution is applied using a titrator for titration. The hydroxyl value is calculated based on the volume consumed. The reagent proportions, criteria for determining the titration endpoint, and requirements for blank test correction are clearly defined. The deviation between parallel test results must comply with the specified limits, providing technical support for evaluating the reactivity of binders and controlling product quality.