The different measurement methods of paint viscosity are discussed

0 Foreword
Coatings under the action of external forces, when the layer flow movement, in its adjacent two layers of molecules between the internal friction, so that the paint produces motion resistance, this characteristic is called the viscosity of the fluid, viscosity is divided into dynamic viscosity, motion viscosity and conditional viscosity. This paper mainly aims at different test requirements in the laboratory, the different systems of coatings, using different test methods for viscosity comparison and analysis.1 Test Method
1.1 Stomer viscosity meter
Stomer viscosity meter (Figure 1) is a laboratory to determine the viscosity of coatings widely used instruments, can measure acrylic paint, epoxy primer, chlorinated rubber paint, epoxy zinc-rich primer, polyurethane varnish and other different system coatings . The measurement principle is that when the torque produced by balancing the weight mass is comparable to the viscosity resistance of the coating, the KU value of the coating is obtained by checking the table, and the measurement range is 40 to 140 KU. Dip the rotor blades into the sample under test until the axle mark, select the appropriate weight from 5 to 500 g weights to place on the weight holder, release the locking knob, start the timing, when the speed is stable at 200 r/min, stop the determination. Due to hardware and software upgrades, the degree of instrument automation is constantly improving, STM-KU2 viscosity meter (Figure 2) can directly display the viscosity KU value, CP value, facilitate the work, improve efficiency, and the instrument to collect data for calculation and related processing, automatically delete data off the center area, improve the accuracy of instrument measurement. The test results of the measured fluid viscosity resistance to the Stommer viscosity blades were more repetitive than the viscosity moment that the rotary rotor was subjected to when the rotary viscosity meter was measured. The advantage of the Stommer viscosity meter is that it is easy to operate, the measurement is complete, simply remove the blades for cleaning, it is convenient to carry out the viscosity determination of high-volume products at the same time. However, Stommer viscosity meter structure is precise, high environmental requirements, vibration, humid environment has a direct impact on the accuracy of instrument measurements, but also shorten the life of the instrument.
1.2 En's viscosity method (coating-1 viscosity metering)
En's viscosity method is applicable to GB/T 266, ASTMD1665, IP212 standards. The principle is that at a temperature of 20 degrees C, 200 mL is the ratio of the time (s) required for the liquid to flow out of enciscosity meter (Figure 3) and the time (s) for distilled water to flow out under the same conditions, in Englada. En's viscosity is a relative conditional viscosity. In accordance with the test requirements, set up a good test instrument, adjust the viscosity meter level, to the viscosity meter in the pot 3 horizontal nails and liquid surface cut, poured into the liquid under test, constant temperature to 20 degrees C. At the beginning of the test, the temperature of the digital thermostat can be set slightly higher, while turning the stirring in the outer pot to speed up the thermostat process. Unplug the plug bar at the same time, press the stopwatch to time and stop when the acceptance bottle 200 mL scale is reached. The standard water value is (51±1) s at 20 degrees C and the temperature score is 0.5 degrees C. The temperature control system of En's viscosity meter can set different temperatures according to the test needs, measure the viscosity of the coating, but its deficiency is that the test device is more complex, cleaning relatively troublesome, especially the products with greater viscosity are not suitable for using Enshi viscosity method.
1.3-4 viscosity meter
-4 viscosity meter is suitable for coating products with an outflow time of less than 150 s. The coating-4 viscosity meter (Figure 4) has a capacity of 100 mL, and when the coating is full of the container, the time flowing from the bottom standard hole determines the viscosity of the coating in s, multiplying the measured value by the correction factor K, i.e. the condition viscosity of the coating. In two parallel tests, the error should not exceed 0.5 s. After the test, the residual liquid should be cleaned, especially the outflow hole, to ensure the finish of the inner wall of the cup. The application-4 viscosity meter is commonly used to measure low viscosity coating products such as floor varnishes and wood coatings. The advantages of applying-4 viscosity meters are simple structure and simple operation. The test data obtained by applying-4 viscosity meter can be adjusted with the results of Ens viscosity meter. However, if the cleaning is not thorough, the outflow hole is easily blocked, resulting in inaccurate measurement results.
1.4 Rotary viscosity meter
Rotary viscosity meter (Figure 5) measures the absolute viscosity of a liquid from 10 to 100,000 mPa s by combining different rotons and speeds. The range reference (Table 1), the rotary viscosity meter can be used to measure the resin viscosity and the TI value of zinc-rich primer epoxy, but also for intermediate products organic bentoft pre-glue viscosity control. When measuring the unknown viscosity of the liquid, in accordance with the principle of the roulette from small to large, speed from slow to fast operation, to prevent the synchronous motor from burning, when the reading pointer is stable in the 30 to 90 minutes range, press the pointer locking rod and motor switch, directly read out the values on the dial, and then multiply the coefficient on the coefficient table, the result is the absolute viscosity of the sample under test (mPa . If the measurement range is exceeded, the measurement can be done by changing the rostring and speed, which is 6 r/min, 12 r/min, 30r/min, 60 r/min. During the measurement process, the lifting screws should be fixed to prevent the motor from falling loose. When loading and unloading the roil, be careful, measure it, clean it, store it in a special box, and install the yellow collar at the shaft connection at the lower part of the motor to protect the sensitivity of the spring wire. Rotating viscosity measurement range is large, so it is widely used in coatings, oils, food, drugs, dyes, inks, adhesives, cosmetics and many other fields. Rotating viscosity meters require a high finish of the roiters of working parts, so corrosive liquids can not be measured.
principle is that the free falling speed of the steel ball is inversely inversely related to the viscosity of the liquid, the greater the viscosity, the longer the steel ball falls. Because bubbles are easy to produce in high viscosity fluids, the measurement results will be biased and parallel tests should be done to reduce errors. The drop ball viscosity meter (Figure 6) is used in the laboratory to determine the viscosity of the resin used in the coating material. The disadvantages of the drop ball viscosity meter are also obvious, because the state of the steel ball needs to be observed, usually only transparent Newtonian liquid can be measured, and the determination of opaque liquid viscosity is not applicable.
1.6 Iwata viscosity cup method
because of its easy to carry, simple operation, is widely used in on-site measurement. When measuring, the Iwata Cup (Figure 7) is immersed in the fluid, and the fluid does not pass the upper end of the Iwata Cup, the cup is raised, and the time is timed according to the stopwatch, when the fluid appears the first break, stop the timing, while doing 3 measurements, the average is the fluid outflow time. Iwata method is suitable for 20 to 105 s outflow time fluid, and the result data should indicate the ambient temperature. Iwata viscosity cup measurement principle and structure is exactly the same as Tu-4 cup, but the size is smaller, is one of the necessary tools for field technical services. However, its deficiency is that it is not enough to measure the high viscosity value of thick primer paint.
2 viscosity unit conversion
absolute viscosity, unit Pa s, 1.0 Pa s s s 10 P s 1 000 cP; Units m2/s, s/ , for the density of the fluid at the same temperature (kg/m3), Ens viscosity Et, units (°), Et=t/K20, t for the test fluid at t s. K20 is the water value of the viscosity meter at 20 degrees C, the application-4 cup viscosity, unit m2/s, (T4-6.0)/0.223, T4 is the 4 cup measured fluid outflow time s, the test data obtained by the different viscosity determination method can also be changed through the table, as detailed in Table 2.
3 Conclusion
the measurements will vary depending on the measurement method, so it is necessary to agree with the supplier and the customer on the test method. Temperature is an important factor affecting viscosity, and the test temperature is usually agreed to be 25 degrees Celsius. In addition to the viscosity meter sent to the local metrology bureau every year, but also can use a stable viscosity standard silicone oil for correction, so that the viscosity meter in a good working condition.