This international standard specifies two categories of method for the determination of the vinyl acetate (VAC) content of Ethylene/vinyl acetate (EVAC) copolymer, for use in the designation of such copolymers in accordance with ISO 21301-1:2019.One category is referred to as reference methods , the other as test methods . The reference methods are used to calibrate the method used for the determination of the vinyl acetate content of ethylene/vinyl acetate copolymers. The "test methods" are other methods which can be used for the determination if they are calibrated using one of the reference methods described in clause 4 provided they show a certain permissible repeatability.