This standard specifies test procedures for determining the melting behavior (melting temperature or melting range) of partially crystalline polymers using two methods: the capillary method and the polarized light microscopy method. The standard notes that results obtained from different methods typically differ by several degrees and are not directly comparable. Method A (capillary method) determines the melting temperature by observing the deformation of the polymer in a capillary tube upon heating, and is applicable to all partially crystalline polymers and their mixtures. Method B (polarized light microscopy method) determines the melting temperature by observing the disappearance of birefringence in the sample under polarized light, and is particularly suitable for polymers containing birefringent crystalline phases. The testing instruments used to implement this standard are primarily polarized light microscope video melting point testers. These devices integrate precision heating stages, polarized light systems, and microscopic observation setups, enabling automatic or semi-automatic observation and recording of sample changes at a constant heating rate in accordance with the standard.