Determination of anti-wear strength of films by OCT standard method

According to the standard method (OCT10086-39 test method), the abrasion resistance of the coating film is determined by the minimum number of sand particles (with a certain degree of dispersion) required to destroy the coating film when sand particles are dropped from a height of 180 cm.

This method is dedicated to the determination of the abrasion of various paint films by grit. The river sand that has been washed and used for the test is first passed through a knot with 236 holes per centimeter, and then the passed sand is passed through a sieve with 2121 holes per centimeter. The degree of coating abrasion is determined using the grit remaining on the joint. (Related instruments: Abrasion Tester)

The instrument for measuring wear (Fig. 150) is composed of a vertically fixed glass primary tube 1 with an inner diameter of 20-30 mm. On the plug upper end, fix a funnel 2 whose tubule diameter is 0.5 mm. The lower end of the pipe is cut into a 45° angle and placed at a distance of 3 to 5 centimeters from the center of the frosted glass of the wooden box 3. Below the tube, a wooden box 3 is placed, and the upper plane of the box (facing the glass tube) forms an angle of 45° with the ground plane. The upper plane of the wooden box has a section with a size of 90x120 mm, on which frosted glass is embedded. Small light bulbs (25 five specials) are housed in the wooden box. The axis of the glass tube should be aligned with the center of the ground glass. The distance from the end of the funnel tube to the center of the frosted glass is 1800 mm.

On the upper plane of the wooden box, there are Yangzi used as test boards. A container for collecting sand particles is placed under the wooden box. The wooden box should have a 100-120 mm high edge to prevent the sand particles from scattering when they fall. Before the test, the sample is applied to the glass plate according to the method specified in the corresponding technical conditions. After drying, or after the time specified in the technical conditions, fix the test panel coated with the sample on the frosted glass and turn on the electric light. Fill the funnel with sand (upper and side flush), and keep the sand at this level throughout the test. The sand flows down through the funnel tube, and the well falls along the tube and is placed on the test plate of the coating film to be tested on the frosted glass.

The sand grains continue to flow down until the paint film abrasion degree at the impact plate surface of the sand grains (relevant instrument: impact Tester). The coating film of the instrument is worn through to the glass. Weigh the number of grams of sand grains (the arithmetic mean value of three measurements) consumed by the total coating film flowing down through the funnel to wear through to the glass surface, which is the abrasion degree of the coating film. Using the device shown in Figure 151, the level of sand in the funnel can be kept constant.

When carrying out the test, it is necessary to use fine sand particles. The above-mentioned instruments have a series of disadvantages, such as the inability to automatically record the results when the test grid is closed, the equipment is heavy, and a large amount of sand is required, so it is easy to foul the test space.

As pointed out by HH Kacharov, the configuration of the sand grains used is of little significance. For example, HH Kacharov checked eight different sand grains from different origins when grinding my glass, and confirmed that these sand grains are actually the same in terms of grinding performance (when the particle size is the same). This is because in the process of grinding glass, the sand grains change their structure under the action of the grinding tool, thus eliminating the distinction between sand grain categories. However, when using grit to pass through the glass tube to test the paint film, the type of grit and its structure have great significance. When using other test methods in which the sand grains themselves are also subject to wear (when using abrasive tools), as the authors have demonstrated, the sand grain structure has no effect on the test results. Use corundum powder or corundum powder with a certain fineness (dispersion) instead, which is more effective than sand grains. (Related instrument: Fineness Meter)