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    Home > Coatings News > Paints and Coatings Market > Water-based paint detection how to correctly select the standard

    Water-based paint detection how to correctly select the standard

    • Last Update: 2020-12-05
    • Source: Internet
    • Author: User
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    With the formulation of national environmental regulations and people's awareness of environmental protection. Traditional solvent-based coating products are increasingly restricted. With the maturity of water-based coating technology, low VOC water-based coatings are more and more applied to various fields
    china
    . The hydration of industrial paint has become inevitable. This paper mainly introduces how to adopt the correct standard in water-based coating testing. Because the important means to determine the quality of coatings is how to correctly adopt and implement technical standards in the test directly affect the measurement results. The technical standards of China's coating industry are relatively complete. Testing method standards cover almost all coatings, coatings and their performance, the correct use and implementation of these technical standards in coating testing not only to ensure the uniqueness of test results, research and development production, use to provide the correct and effective data, but also promote the healthy and standardized development of the coating industry. Beginning in the 1980s, the standard of testing methods in the national standard gradually became in line with international standards, and the standard of coating testing methods was confirmed in 1989, and the original mandatory standards were generally changed to recommended standards, which reserved a large choice of options for the selection of standards. It also puts forward higher adaptability requirements for the implementation of standards. In practice, only by fully understanding, carefully selecting and strictly enforcing the standards can we play the normative, supporting, guiding and supervising role of technical standards. Below to paint detection of several links——— sampling, paint film preparation, film conditioning, testing and so on how to correctly pick and carry out some discussion.1 Sampling
    GB3186-1982 (1988) Paint Product Sampling is one of the few mandatory standards in coating testing standards. You can see the importance of sampling for testing. The key to sampling is to ensure sample representation, that is, representative samples can detect the correct results, GB3186 for different forms of paint products sampling regulations, which is essential: ( 1) sampling site; (2) is the number of samples taken. Under full mixing conditions. The sampling site should be taken from the top, middle and bottom three levels. The number of samples shall be determined according to the number of barrels (n) handed in, and the standard provisions are greater than
    , i.e. samples should be taken from more than
    barrels, and the sample size shall ensure the need for the amount of test items and the need for sample preparation, and take them at once. The actual production, acceptance, do not pay much attention to sampling situation many, there is a great deal of randomness, not only not by part and quantity sampling, but also to do different testing items, to provide different samples, paint all testing items can not ensure that from the same sample, resulting in an increase in the credibility of the results.
    2 Paint film preparation
    lacquer film preparation is the first process of paint film performance testing, it is in the product-specified standard test plate (see GB/T 9271-2008 paint and varnish) on the preparation of paint film. National standards commonly used in paint film preparation are: GB/T1727-1992 Paint Film General Preparation Method, GB/T1765-1979 (1989) determination of wet heat, salt spray resistance, weather resistance (artificial acceleration) paint film preparation method, GB//T6741-1986 Uniform lacquer film preparation method rotating lacquer method) and cB/T1736-1979 (1989) insulated paint film preparation method, HG/T3334 electrophoresis paint film preparation method. For example, water-based coatings are prepared according to GB/T1727 paint film, for general performance testing; Paint films prepared according to GB/T1765 are used for the determination of specific performance. GB/T6741 the provisions of the paint film preparation, belongs to the paint film general preparation method, more used for arbitration testing. In addition to the paint film preparation of substrates, substrate surface treatment, coating methods, curing conditions, etc. are clearly defined, another important feature is often ignored, that is, thickness. Because the thickness of the paint film has a great influence on the test results, the prepared paint film conforms to the specified thickness before it can be used for testing. The test report should indicate the thickness range of the paint film while reporting the test results. Common irregular behavior is that mechanical properties such as flush resistance and adhesion, flexibility and other paint film thickness is ultra-thin, and weather resistance and other tests when the coating is super-thick, so that the test results are easy to pass, but lost authenticity and comparability. Common test reports, the corresponding part only gives the test results, not the thickness of the paint film, can not determine the test results obtained under what thickness.3 Paint film state adjustment
    state adjustment refers to the paint film test should be placed in the specified environmental conditions, to maintain a predetermined time of the operation process. This link has a great influence on the test results, but it is often overlooked. The standard ambient conditions given by GB92718 are: temperature (23 ± 2) degrees C, relative humidity (50 ± 5 percent) or (23 ± 2) degrees Celsius. State apoptosis is a link in paint film preparation, so the expected time is specified in the corresponding paint film preparation method standard. According to GB/T1727 for general performance test paint film preparation, self-drying paint and drying paint for 48 h and 24 h status adjustment, and then carry out a variety of performance tests; According to GB/T1765 preparation paint film performance test, self-drying paint and dry paint condition adjustment time is 7 days and 1 day, respectively.4 Test environment
    mainly refers to the temperature and humidity environment of the test. Some testing programs require very strict environmental conditions, such as paint viscosity. For the performance of the paint film testing environmental conditions, in addition to the test method standards are clearly defined, the temperature and humidity of the test according to GB9278 regulation and state regulation is the same. When the actual test test, the environmental conditions often do not meet the standard requirements, and some testing items do not need strict control. For non-arbitration purposes, the test ambient temperature and humidity may be carried out under non-standard conditions, but the actual temperature and humidity range of the test environment should be indicated in the test report.5 Test
    coating testing methods, data processing, results determination and other technical content are reflected in the corresponding testing method standards, strict implementation of these standards, you can obtain reliable results. Many of the current technical standards of testing projects at the same time there are several method standards, the bid and the standard must pay full attention to their scope of application to prevent misuse. Here are some discussions about the marking of several test items.
    5. 1 Paint film thickness measurement
    ' common paint film thickness measurement method standards are "GB/T1764 paint film thickness determination method", GB/T13452. 2 color paint and varnish film thickness determination, the former comes from the Ministry of Chemical Industry standard conversion, the method is intuitive and simple; The latter and so on using IS02808, although it does not include all the thickness measurement of the general method, but it gives a variety of different conditions of paint film thickness determination of a variety of applicable methods, such as epidural, soft film, wet film, magnetic substrate, non-magnetic substrate, etc. , the scope of application is accurate, the technical means of measurement is also broader. In addition, there are GB/T4956 and GB/T4957, the former provides for magnetic metal substrate E non-magnetic cover thickness measurement———magnetic method, the latter provides non-conductive covering thickness measurement on non-magnetic substrate ——— eddy current method, these two standards are actually GB/T13452. 2 The relevant methods of expansion and widening, based on the same measurement principle, the difference is that its measurement object is not limited to the paint film. For ceramics, glazed porcelain, some chemical conversion film, etc. are also applicable, it is important to remind that the eddy current method can not be used in coatings containing metal pigments, because metal powder vortex affects the test results. The above-mentioned standards involve more methods, the applicable conditions are different, when picking, standards should pay attention to distinguish.
    5. 2 Coating fineness measurement
    the most common and convenient method of coating fineness is scraper fine measurement. GB/T1724 Paint Fine Determination and GB/6753. 1 Coating grinding fineness determination two standards, are to scrape plate fineness meter as a measuring tool, but its structure, score value, measurement accuracy determination standard and applicable fineness range, etc. are different, Table 1 lists the size difference between the two standard scraper fineness meters, Table 2 lists the two standards of applicable range, accuracy.
    two standard scales, even if the spread scale is the same, and the accuracy of the readings is different because the two standard fineness determination methods are different. In practice, it is necessary to strictly distinguish between the two standard scraper fine scale, the correct implementation of the applicable scope and decision rules, in order to get the correct results, must not be confused.
    5. 3 Paint film adhesion determination
    (GB/T5210 coating adhesion determination method) can be quantitatively measured adhesion, but the test procedure is complex, especially the test preparation volume is large. In general, less is used. Use when other methods are inconvenient to determine (e.g. super-thick coatings) or when requiring defined technical data. The GB/T1720 Coating Adhesion Determination Method and the GB/T9286 Varnish and Color Paint Coating Film Scratch Test can only obtain qualitative adhesion grades. GB/T1720 is the long time used in coating adhesion determination in China. It is widely used. GB/T9286, i.e. the cross-blocking method can be carried out directly on the coated product, and 0, 1, 2 levels are given as pass levels. In the water-based coating testing, the customary selection of the ring method and the rowing method is fast and simple.
    5. 4 Paint film flexibility determination
    GB/T 1731-93 (paint film flexibility determination) operation is simple and convenient, by most manufacturers in China. GB/T 6742-86 (paint film bending test (cylindrical shaft)" and ISO 1519: 2002 "color paint and varnish bending test" is the same method, GB/T6742-86 is the standard of ISO 1519: 1973, both methods are the use of the whole plate test, and the palm does not directly contact the paint, eliminating the impact of the human body on the test plate elevated temperature. GB/T 11185-89. The paint film bending test (conical shaft) also uses the whole plate test, and avoids the discontinuity of the results brought about by the test with a set of conventional shaft rods.
    5. 5 Salt water resistance determination
    salt water resistance determination is usually carried out according to GB/T 9274-88 medium immersion method. Substrate material, substrate treatment and paint film thickness should be strictly in accordance with product standards. The uniformity of the film thickness, the drying of the paint film, whether the surface of the paint film is defective (e.g. brush size, whether there are particles, shrink holes), and the quality of the model sealing edge may have an impact on its performance test results. For each test, the solution should be replaced or carried out as required. Preferably a sample with a container, especially the test fluid has a high electrolyte effect, immersed model should be from the groove wall, groove bottom at least 30 mm, the model should be at least 30min interval between each other, in order to avoid the mutual influence between the models, electrochemical corrosion, speed up damage.
    5. 6 Salt mist resistance determination
    Salt mist test sample substrate selection, treatment, preparation methods, maintenance time generally in the product standards have corresponding requirements, but also by reference to GB/T 1765-89 "to determine moisture-resistant heat, salt spray resistance, weather resistance (artificial acceleration) paint film preparation method" provisions of preparation, maintenance of the model. The back and perimeter of the test plate can be applied using the test sample or a coating system known to have better corrosion resistance. If you want to do a dash (cut, scratch, scratch) test, you can use a dashing tool with tungsten carbide (carbide) tip (e.g. GB/T 1771-91 recommended GB/T9286 single-edged cutter and ASTMD1654-2005 recommended ANSI B94. Type E in 50) but similar tools such as blades, needles, scalpels, scissors, etc. are not allowed.
    a uniform V-shaped bright line with no burrs on the surface of the model, evenly across all coatings on the substrate. If necessary, it is agreed that several lines can also be drawed, the quality of the dash can be observed with the help of a low magnifying glass. Common forms of dashing: two intersections, a straight line parallel to the long edge, two lines parallel to the long edge, two vertical lines, V-shaped, and so on.
    a sample inspection, the test sample can be removed from the box and compared to the standard board in sufficient light or light. The evaluation can be carried out by reference to the requirements of the relevant product standards, or by reference to GB/T 1740-89 (paint film moisture-resistant heat determination method), ASTMD1654-92 "painted paint or paint samples have been subjected to the assessment of the corrosive environment" and other evaluation standards, the model line and unlined area one-way erosion spread and foaming, rusting, shedding, color change and other assessment standards. No assessment is made within 5 mm of the perimeter of the model and around the hole, and the final result is based on two of the three test boards with consistent levels. The common methods of evaluation at the test model dash are: air blow-off method, washing and scraping method, tape tearing and removal method.
    above from the paint testing several links to talk about some of the experience and understanding of marking and standards, aimed at explaining the serious distinction between the characteristics of various technical standards and adaptability, is the paint testing worthy of great attention to the problem. Only careful digestion of technical standards, the correct selection of standards, strict implementation of standards, in order to ensure that paint performance testing specifications, accuracy, confidence can be steadily improved.
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