This is a standard test method for determining the thermal shrinkage properties of dipped yarns, cords, and threads. It specifies the measurement of the free shrinkage length change of a sample within a specified time at a fixed test temperature of 125°C using a thermal shrinkage tester, in order to calculate its free thermal shrinkage rate. The standard applies to industrial fabric reinforcement materials, such as those used in conveyor belts and rubber hoses. This determination is crucial for evaluating the dimensional stability of reinforcement materials during vulcanization or in high-temperature service environments, making it one of the key tests for controlling the quality and performance of rubber products, such as tires and conveyor belts.