What are the precautions for measuring the viscosity of hydroxypropyl methylcellulose? When we test the viscosity of cellulose. In order to ensure the accuracy of the test results, the following four aspects need to be paid special attention to. As a HPMC Suppliers, share with you.
1. The performance indicators of the instrument must meet the requirements of the national metrological verification regulations.
The hydroxypropyl methyl cellulose viscosity measuring instrument is used in the test cycle. If necessary (the instrument is often used or is in a qualified critical state), perform an intermediate self-check to determine that the measurement performance is qualified, and the coefficient error is within the allowable range, otherwise it cannot Obtain accurate data.
2. Pay special attention to the temperature of the liquid being measured.
Many users ignore this point and think that the temperature is almost irrelevant. Our experiments show that when the temperature deviation is 0.5℃, the viscosity deviation of some liquids exceeds 5%, and the temperature deviation has a great influence on the viscosity, temperature and viscosity. Therefore, special care should be taken to keep the temperature of the measured liquid near the specified temperature point, and for accurate measurement, it is best not to exceed 0.1°C.
3. The choice of measuring container (outer tube).
For the double barrel rotational viscometer, please read the instrument manual carefully and match the rotor (inner barrel) accordingly. External cylinder, otherwise the measurement result will be greatly deviated. For a single-cylinder rotational viscometer, in principle, the radius of the outer cylinder is required to be infinite. The actual measurement requires that the inner diameter of the outer cylinder, that is, the measuring container, is not less than a certain size. For example, the NDJ-1 rotational viscometer requires a measuring beaker or straight tube container with a diameter of not less than 70 mm. Experiments have shown that, especially when the No. 1 rotor is used, if the inner diameter of the container is too small, it will cause large measurement errors.
4. Correctly select the rotor or adjust the speed so that the value of the grid is between 20 and 90.
This type of instrument uses dials and pointer readings. The stability and reading deviation are combined with 0.5 grids. If the readings are too small, close to 5 grids, the relative error caused by more than 10%, if selected If the correct rotor or speed reading is 50, the relative error can be reduced to 1%. If the value is displayed above 90, the torque generated by the spring is too large, which is prone to creep and damage the hairspring, so we must choose the rotor and speed correctly.
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