- August 11, 2021
- Posted by: admin
- Category: News
In order to make better use of this product, we need to understand its related knowledge and performance. Today we will first understand how to test the viscosity of this product, please be sure Read it carefully.
The viscosity mentioned here refers to the apparent viscosity, which is an important index of hydroxypropyl methyl cellulose. Common measurement methods include rotational viscosity measurement, capillary viscosity measurement, and falling autumn viscosity measurement.
Previously, the measurement method of hydroxypropyl methylcellulose was capillary viscosity method, using a Ubbelohde viscometer. The measurement solution is usually a 2% aqueous solution with the formula: V = Kdt. V is the viscosity, the unit is mPa.s, K is the constant of the viscometer, d is the density at constant temperature, t is the time from the top to the bottom through the viscometer, the unit is second s.
The operation is more tedious in this way. If there is insoluble matter, it is easy to cause errors and it is difficult to identify the quality. Rotational viscometer is now commonly used to determine its viscosity. The NDJ-1 viscometer is generally used in China, and its formula is η = Kα. η is the viscosity, the unit is also mPa.s, K is the coefficient of the viscometer, and α is the reading of the viscometer pointer.
Detection method of hydroxypropyl methylcellulose 2% viscosity:
1. This method is suitable for the determination of the dynamic viscosity of non-Newtonian fluids (solutions, suspensions, emulsion dispersion liquids or surfactant solutions) of non-Newtonian fluids.
2, instruments and appliances
2.1 Rotary Viscometer (Chinese Pharmacopoeia requires the use of NDJ-1 and NDJ-4)
2.2 Constant temperature water bath constant temperature accuracy 0.10C
2.3 Thermometer division 0.20C, after periodic inspection.
2.4 Frequency meter Viscometers (such as NDJ-1 and NDJ-4) using frequency stabilization measures must be reserved. Accuracy 1%
3.Operation method: Weigh 8. Og sample accurately, put it into a dry, tared 400mL high-leg beaker, add about 100mL of 80-90 degree hot water, stir for 10min to make the dispersion uniform, add cold water while stirring At the same time, continuously stir for about 30min to make a 2% (w / w) solution. Put it in an ice bath in the refrigerator to cool the surface to a thin layer of ice. Salary.
3.1 The installation and operation of the instrument should be performed according to the instruction manual of the instrument, and the appropriate rotor and speed should be selected according to the viscosity range of the test product and the provisions of the pharmacopoeia under the text of the product.
3.2 Adjust the temperature of constant temperature water according to the measurement under each drug.
3.3 Take the test sample and place it in the container specified by the instrument. After constant temperature for 30 minutes, measure the deflection angle (a) according to law. Turn off the motor and restart the measurement again. The difference between the measured value and the average value must not exceed 3% of the average taxi. Otherwise, the third measurement should be performed.
3.4 Take the average value of two measurements and calculate it according to the formula to obtain the dynamic viscosity of the test product.
4. Record and calculation
4.1 Record the model of the rotary viscometer, the rotor number and speed used, the viscometer constant ((K ‘value), the measurement temperature, and the value measured each time.
4.2 Calculation formula
Dynamic viscosity (MPa “s) = Ka where K is a viscometer constant a measured with a standard solution of known viscosity a is the deflection angle.