This standard is a specialized test method used to evaluate the resistance of powdered polyvinyl chloride resin to degradation under heated conditions. The core principle is that polyvinyl chloride decomposes and undergoes color changes at high temperatures. Therefore, by placing the sample in a thermal test chamber (or aging oven) at a specified temperature for a set period and measuring the decrease in whiteness using a whiteness meter, its thermal stability can be characterized. The testing process imposes clear requirements on the precision of the instruments, particularly stipulating that for arbitration tests, a whiteness meter with a d/0 illumination and detection geometry must be used. This method provides a direct reference for evaluating the processing and application performance of PVC resin.