Although coating is also a kind of chemical product, it is different from general chemical products in terms of its composition and use. Therefore, according to the characteristics of coating products and applications, the quality testing of coating products has different characteristics compared with general chemical products.
(1) Coating film inspection is a key quality inspection of coating products, which is mainly reflected in the performance of the coating film. This is because the coating is a polymer colloid mixture composed of various raw materials, which is used as a supporting engineering material. Unlike general chemical products, the quality can be judged from their chemical composition. The coating product is mainly to check the performance of the coating film formed by it as a material coated on the object. Therefore, when evaluating the quality of the coating product, it is necessary to check not only the coating product itself, but also the performance of the coating film. This is the main one. The focus of paint inspection is to detect the performance of the coating film, while the inspection of the state of the paint product itself is mainly to inspect the consistency of product quality. Therefore, the film-forming process of coatings and the performance test after film-forming are the basis for quality evaluation of coating products and the main content of coating quality assessment. The detection methods in this area have developed the most and the fastest.
(2) The quality inspection of paint products should include the inspection of construction performance. There are many kinds of paint products with a wide range of applications. The same paint product can be applied in different aspects. Each paint product can play its role of decoration and protection only after it is applied on the object to be coated by the construction department to form a continuous and firmly attached coating film. This requires that each coating needs to have good construction performance, otherwise it will not achieve the expected effect. Therefore, when the quality inspection of the coating is carried out, its construction performance needs to be checked.
(3) The physical method should be the main method, and the chemical method should be used as a supplement to check the performance of the coating film. The physical method is also the main method of inspection, and the chemical composition of the coating film is rarely analyzed. It is not possible to completely judge its quality status based solely on chemical composition analysis, but to see whether it meets the required material properties. Therefore, the detection of coating performance is mostly based on physical inspection. In addition, in the inspection of physical properties, the result measured by one detection method is often a combination of several properties. For example, the bending test commonly used to measure flexibility reflects not only the flexibility, but also the hardness and attachment of the coating. Strength and extensibility.
(4) It is necessary to select the corresponding substrate and prepare the sample plate according to the requirements. When checking the performance of the coating film, it is necessary to prepare the sample plate in accordance with strict requirements in advance, otherwise the correct result will not be obtained. Therefore, in the quality standards of each coating product, the method of preparing its coating film model is stipulated as one of the standard conditions for the quality inspection of coatings. In order to imitate the actual conditions as best as possible, most of the coating performance tests are carried out on the corresponding substrates, so the selection of the test substrates has a certain relationship with the test results, and more importantly, the preparation process and method of the test coating film on the substrate. Quality has a significant impact on test results.
(5) It is necessary to select a more suitable method among various test methods. After years of development, after a test item has developed a variety of test methods, some methods are still retained because of their unique characteristics, which forms the test method and test method. Variety of instruments. A variety of testing methods for coating products coexist. Different methods of the same testing item are tested from different angles, and the results are often different. Therefore, when testing coatings, a more appropriate method should be selected from various testing methods for product performance.
(6) The evaluation of some test results is difficult. Although the test methods have been developed for many years and are expressed by the most quantitative values, there are still some test items that are compared with the standard conditions.Or expressed by the degree of change such as "no change", "slight change", etc., there are many interference factors when evaluating the results. In addition, the detection methods are not yet fully instrumented, and some visual observations are likely to cause subjective errors, which increases the difficulty of evaluating test results. Therefore, some inspection items stipulate that 3 or more samples are used for testing at the same time, and the majority of the results are used as the final judgment.
(7) It is necessary to combine multiple indicators to balance the judgment of paint performance. The paint product has passed the test, and the final result evaluation is more comparable to similar products, but less comparable to products with different compositions. Since the testing items are multifaceted, the final judgment on the performance of the coating needs to be comprehensively balanced by various indicators. The comparison of a single indicator cannot explain the performance of the product.
People often encounter such a dilemma. In the development of new products, due to the different formulations obtained from a coating experiment, it is difficult to balance the performance, and often only a good formulation can be determined subjectively and qualitatively. When choosing a paint variety, in order to meet a specific painting requirement, the paint needs many properties, and some properties are often in conflict with each other. There is no "satisfactory paint" that can achieve all the properties well. This is to evaluate which kind of coating has better overall performance and is closer to the "satisfactory coating", so as to make a choice. In 1992, M.Simakaski (Drexel University) and C.Hegedus ( Naval proposed a comprehensive performance evaluation method for coatings and coating systems. This method won the Hendy Paper Award in 1992. The coating TPE method is not an experimental method, but a method of comparing and evaluating coatings based on experiments and performance test results. Its basis is the zero-maximum technique in statistical methods, and it is a method to determine the contribution of multiple factors to the overall performance. , is not to optimize the properties of the coating, but to maximize the contribution of various properties to the comprehensive performance of the coating, and to make a quantitative and objective selection by comparing the comprehensive properties to obtain the TPE grade. The TPE method provides a more objective method for evaluating the comprehensive performance of coatings, which is of practical significance for the development and selection of new coatings.