12 testing methods of coating performance

2021-07-07   Pageview:191

1, The condition of the original paint in the container, such as whether there is layering, crusting, thickening, gelling, sinking or lumping, etc., and whether it can be re-mixed into a uniform state. The test method is visual inspection.

2, Dispersion fineness dispersion fineness, also known as grinding fineness, is a measure of the degree of dispersion of the system in the face filler, is a standard fineness meter under the specified conditions, the reading obtained in the standard fineness meter, the reading indicates the depth of the groove somewhere in the fineness meter, generally expressed in μm. Grinding fineness is small, which means good dispersion, high utilization of color filler, strong covering power of coating, and smooth appearance of coating film. National standard GB/T 1724, GB/T6753.1 and international standard ISO1542 are used scraper fineness meter method.

3, Paint appearance of latex paint after drying visual inspection, such as paint flat, uniform, no pinhole, shrinkage, hanging, no obvious brush marks, color and standard board difference is not obvious, gloss in line with the requirements (light, semi-light or no light) is qualified. The appearance of the paint is an important measure of paint quality, for the color control requirements of high commonly used color difference meter test, test methods have GB GB/T11186.1~3 or ISO 7742-1~3, gloss instrument measurement method GB/T9754, ISO 2813, etc.

4, PH value is a measure of the concentration of hydrogen ions in solution. During the storage of paint, the change of ph value can indicate the stability of paint and the change of paint performance.

5, Thickness (low shear viscosity) refers to the internal resistance of fluid flow. GB/T9626 and ASTM D562 are used to determine the viscosity of Stormer. The viscosity of most emulsion paints is about 150 ~ 300g/100r.

6, Freeze-thaw stability of latex paints subjected to freezing and subsequent melting process (cycle test), the ability to maintain its original state, that is, the ability to not occur solidification, return to coarse or excessive viscosity increase and other ills. GB/T9628 and ASTM D2245 both use a 500ml can of paint placed in an environment of -18 ℃ for 17h, and then placed at room temperature for 7h to dissolve, this is a cycle, the general emulsion paint for 1 ~ 5 cycles, to assess the performance changes for 0 ~ 10 levels The one without change is good.

7, Drying time refers to the specified drying conditions, a certain thickness of the liquid film to the formation of solid paint time required, it is determined by the composition of the paint and environmental conditions. Paint drying too slow will adhere to dust, insects, etc. and make the film appearance worse, such as in the outdoor encounter rain, etc. will also lead to uneven appearance. Most latex paints reach the finger touch dry time of l ~ 2h, low light and no light latex paint usually a few hours to more than ten hours can be repeated painting, semi-light and light latex paint recoating time is generally greater than 18h, which should be controlled according to the ambient temperature and humidity flexible control of the thickness of the one-time coating. Paint to achieve the best performance, generally to dry a few days or even weeks. Measurement methods are CB / T 1728, CB / T 6753, ISO1517, GB / T9273, GB / T 9280, ISO 3678 and ASTM D1640, etc.

8, The contrast ratio is the ratio of the reflectivity of the same coating on the black and white substrate coated in the specified reflectivity. When the contrast ratio is ≥ 0.98, the coating can be considered to have completely covered the substrate, so the contrast ratio can be used to judge the covering power of the coating to partially eliminate the artificial error. GB/T 9270, GB/T 5211, ISO2814, ASTM D2805 all use reflectometer method to determine the contrast ratio.

GB/T 9264, ASTM D 4400 are available in different sizes of multi-tooth scraper (such as 50 ~ 275μm, 250 ~ 475μm and other specifications). 250 ~ 475μm and other specifications) scraping after the 90 ° rotation of vertical placement, coating thin strip on the top, coating thick strip on the bottom, depending on the last of the film not flowing down the strip for the film thickness not hanging.

ASTM D4707 uses certain specifications and paint color contrast drawings to collect the size and density of paint points spilled on the drawings when roller coating, and then compare with standard drawings to assess.

11, Alkali resistance assesses the resistance of the coating film to alkali erosion. Emulsion paint included in the alkali resistance index, mainly considering the impact of alkaline substances such as cement on the coating. GB / T9265 using saturated lime water impregnation method of determination, ISO also provides for a variety of media impregnation method.

12, Scrub resistance scrub resistance is the ability of the coating film under the specified conditions, repeatedly scrubbed with the specified washing medium and maintain its undamaged. Measurement methods are GB / T 9266, Astam 2486, etc.

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