The visual inspection method is a qualitative visual method. When judging the dispersion of carbon black, the dispersion grade of carbon black is evaluated by comparing the observed incision of the sample with a set of standard photographs, and the results are expressed in numerical values. This is a method recommended by the American Society for Testing and Material (ASTM). The specific method is to tear or cut the mixture sample (some need to be properly processed) to expose its fresh surface, and observe it with the naked eye, preferably under a magnifying glass or a low magnification binocular microscope , Compare the dispersion of carbon black with a group of 5 standard photos, and then evaluate the grade. So this method is also called the comparative sample method. The visual dispersion level is related to some important physical properties of the mixture.

This method can be divided into 5 grades when evaluating the dispersion grade of carbon black. A level of 5 indicates that such a dispersed state brings these physical properties closest, while a mixed state of 1 causes these properties to decrease significantly. The agglomeration counting method relies on the percentage of the area of carbon black agglomerates in the mixture slice of the optical microscope to assess the degree of dispersion of the mixture. Since this method involves direct measurement, it is more accurate than the visual observation method for quantitative determination and is also a method adopted by ASTM.

The specific method is: cut the mixture into thin enough slices, and after certain treatment, put it under transmitted light, and observe the carbon black agglomerates in it through an optical microscope. The magnification of the optical microscope is between 75 and 100 times. The eyepiece used for counting contains a 1cm2 grid divided into 10,000 small squares. Calculate the area occupied by all carbon black aggregates not less than 5 μm. Based on the known carbon black content in the material, the percentage of carbon black agglomerates with a size of 5 μm can be calculated, expressed as “percentage of carbon black dispersion”. Optical microscopy and electron microscopy are commonly used qualitative methods to directly observe the morphological structure of the mixture. There are many methods to directly judge the mixed state, such as the photoelectric method. The principle is: the 40um sample sheet made of a mixture of LDPE and carbon black is processed and scanned under a microphotometer. Due to the uneven size and distribution of the carbon black micelles, the transmitted light intensity It's different.