Abstract: The assessment method of the degree of pigment or carbon black dispersion in polyolefin pipes， fittings， and compounds based on the Chinese national standard GB/T 18251—2019 is the current standard method for measuring the dispersion of carbon black in plastic pipes. This paper mainly discusses the thickness range of samples， thickness measurement method， and the sample shape， width， and problems encountered in sample preparation through a slicing method in the process of carbon black dispersion measurement based on this standard. The thickness of the sample was an important parameter for the preparation of samples. The specific measurement method was not given in the current standard and therefore should be supplemented. The microscope measurement method was recommended for use. The thickness range （20±10） μm of carbon black dispersion sample presented in the standard is not suitable. It was found that the thickness of the sample used for the test should be less than 10 μm. The standard does not give the shape and width of the sample prepared by using a slicing method. A square sample with a width of 4 mm was recommended for use. During the slicing process， the sample could be cut to the specified thickness range. This encountered problem could be solved through cutting the sample after low?temperature freezing.

Key words: carbon black dispersion, tablet pressing method, slicing method