This standard specifies the constant tensile deformation method for determining the environmental stress cracking resistance of thermoplastic plastics in chemical media (such as cleaning agents, oils). The method involves applying and maintaining a constant tensile deformation on plastic specimens, immersing them in a specific medium, and observing and evaluating the occurrence of cracks on the specimen surface after a specified time or cycle, thereby assessing the material's cracking resistance. This method is suitable for comparing the durability of different plastics or the same plastic in different chemical environments. The test typically requires a material testing machine capable of providing precise constant load or constant strain, and often needs to be combined with an environmental test chamber capable of holding chemical media.