Focus on Cellulose ethers

How to measure the viscosity of HPMC?

What are the precautions for measuring the viscosity of hydroxypropyl methyl cellulose HPMC? When we test the viscosity of cellulose. In order to ensure the accuracy of test results, special attention should be paid to the following four aspects.

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 frequently used or in the critical state of qualified), an intermediate self-test is performed to ensure that the measurement performance is qualified and the coefficient error is within the allowable range, otherwise accurate data cannot be obtained.

2. Pay special attention to the temperature of the liquid being measured.

Many users ignore this 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 is more than 5%. The temperature deviation has a great impact 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℃.

3. Selection of measuring container (outer tube).

For two-barrel rotary viscometers, read the instrument manual carefully and match the rotor (inner cylinder) accordingly. External cylinder, otherwise the measurement results will be greatly deviated. For a single cylinder rotational viscometer, the radius of the outer cylinder should be infinite in principle. The actual measurement requires that the inner diameter of the outer cylinder is not less than a certain size. For example, the NDJ-1 rotary viscometer requires a measuring beaker or straight tube container not less than 70 mm in diameter. Experiments have shown that large measurement errors can result if the inner diameter of the vessel is too small, especially when rotor no. 1 is used.

4, correctly choose the rotor or adjust the speed, so that the value of the power grid between 20-90.

This type of instrument uses dial plus pointer readings, and the combination of stability and reading deviation has 0.5 grids. If the reading is too small, approaching 5 grids, the relative error can be more than 10%. If the correct rotor is chosen or the speed reading is 50, the relative error can be reduced to 1%. If the value shows above 90, the torque generated by the spring is too large, which is prone to creep and damage the hairspring, so we must correctly choose the rotor and speed.

This paper introduces the matters needing attention in measuring the viscosity of hydroxypropyl methyl cellulose, hoping that the above content can help you test. KIMA CHEMICAL adheres to the principle of “innovation, customer first, quality first”. The concept of enterprise development is to build on long-term trust and development, constantly innovate equipment and technology, to green environmental protection and high-tech development. The company is willing to cooperate with domestic and foreign high-quality products and friends for a long time, sincere cooperation.

Post time: Jun-18-2022
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