This standard specifies the technical method for determining the glass transition temperature (Tg) of polymers using dynamic mechanical analysis under a constant heating rate. The glass transition temperature refers to the characteristic temperature at which the amorphous regions of amorphous or partially crystalline polymers transition from a hard and brittle glassy state to a high-elastic or viscous flow state. This method is applicable to a variety of materials, including unreinforced plastics, rubber, adhesives, foams, and fiber-reinforced composites. Its core technical principle involves using a dynamic mechanical analyzer to apply controlled alternating stress to the sample, measure changes in its dynamic modulus and loss factor, and thereby accurately determine the glass transition temperature.