GB/T 4 2919.1 - 2023 is a general part of the standard for the determination of thermal conductivity and thermal diffusion coefficient of plastics. It clarifies the scope of application of the series of standards, expounds the basic principle of measuring thermal performance parameters, and standardizes the definition of terms, symbol descriptions, general requirements for samples and test environmental conditions common to various measurement methods. This general rule lays the foundation for subsequent specific measurement method standards, ensures the coordination of all parts, helps to accurately determine the thermal performance of plastics, and provides thermal performance data support for its rational application in various industries.