A summary of the method of measuring the percentage content of the volume of the coating without volatiles

The non-volatile volume percentage content of the coating is commonly known as the volume solid content of the coating, which refers to the percentage of the volume of the non-volatile material obtained by the coating product after the specified uniform thickness curing or drying at the specified temperature. Using this parameter and using a simple conversion, we can get the values such as the dry coating film density and theoretical coating rate of the coating, so this is a very important parameter to guide the coating construction of coating products, calculate the amount of paint used and account for the construction cost.1 measurement method introduces the
currently commonly used method of measuring the volume percentage content of non-volatile coatings are as follows:
1.1 Method I: Simple and practical method
metric measurement of non-volatile mass content of paint products N V m ( % ) (baking method) and density ρ 1 (g/ml) and the density ρ 2 (g/ml) of the main solvent parts in coating products, the theoretical density of dry coating film ρt (g / m l) and the non-volatile volume percentage content N V (% )
China
) of coating products can be obtained by formula (1) and (2), respectively.
2 Test Method Discussion
2.1 Method one is a combination of simple test and calculation processes, the results are more reliable than purely theoretical calculation methods. Pure theoretical calculation method only considers the addition of various raw materials in the formula (mass or volume), and then according to the volatile status of various raw materials to make a simple addition and get the volume of the cured dry coating film.
the actual composition of resins and solvents may not be consistent with the simple addition and value of each component volume. There are three main reasons:
first, the shrinkage or expansion of resins and solvents affects the volume of the composition

; By simply measuring the mass content and density of non-volatile materials of coating products and calculating the density of the main solvent parts used and calculating them according to the formula, this method can greatly overcome the shortcomings of pure theoretical calculation methods, and involves fewer types of instruments, and the testing process is simple. The method is currently used frequently in the field of automotive coatings and is being adopted by the International Organization for Standardization (ISO) to be translated into international standards in order to promote its application. The disadvantage is that this method is not suitable for coating products that exceed the critical pigment volume concentration, because the unfilled voids between pigment particles increase after drying of these coating products, so that the volume of the real inter
dry coating film is larger than the theoretical volume.
2.2 Method II can be used on the premise that the paint film is completely flat, the film thickness is uniform, wet film thickness and dry film thickness can be easily measured. Using the general brush coating, spray method is difficult to obtain this requirement of the paint film, it is recommended to use the scraping method, such as in a smooth smooth polyester film or glass plate with a wet film preparer to prepare the appropriate thickness of the paint film, and choose the appropriate method to test the wet film thickness and dry film thickness. Suitable methods for testing the thickness of paint film can be selected from the national standard GB/T 13452.2-92 "Measurement of the thickness of paint and varnish film" or the international standard I S O2808:1991 "Measurement of the thickness of color paint and varnish film". The disadvantage of this method is that the application range is narrow, the preparation requirements of the paint film are too high, and a variety of instruments are required to test the thickness of the paint film.
2.3 Method III is the method used in the international standard ISO3233:1998 "Color paint and varnish - by measuring the density of the dry coating to determine the percentage content of the non-volatile volume of the coating". The method has the same drying conditions when determining the non-volatile mass content of the coating and the non-volatile volume percentage content, and directly simulates the drying conditions during the coating construction, which can better reflect the actual construction situation, and the results are more credible. However, the experiment found that although this method is suitable for most coating products, it is not suitable for coating products with very little viscosity and coating products with easy separation of pigments and resins.
coating products with minimal viscosity, can not obtain the desired thickness of the coating through two immersion operations and samples may drip during the drying process and affect accurate determination;
The original national standard GB/T 9272-88 "the determination of non-volatile part capacity in liquid coatings" by baking method to obtain the paint's non-volatile mass percentage content, and then through conversion to obtain the paint's non-volatile volume percentage content, the process can not well reflect the actual construction of the paint and can not obtain the density value of the dry coating. 2 0 0 6 years in China in the revision of the national standard GB/T 9272 combined with ISO 3233:1998 and GB/T9272 - 88 methods, different treatment of different coatings, is a very perfect method, high accuracy of testing. At present, the national standard has completed the approval, will soon be released, for the vast number of paint users to learn from the use. The disadvantage is that the whole testing process of this method looks more complicated and has many steps, but once you are familiar with the whole process, you can complete all the experiments well.3 Conclusion
Each of the three test methods has advantages and disadvantages, and coating producers and users can choose the appropriate test method according to the characteristics of their paint products and testing needs.