HPMC viscosity

How to test the viscosity of hydroxypropyl methylcellulose

In the past, the determination method of hydroxypropyl methylcellulose was capillary viscometry, using an Ubbelohde viscometer. Usually the measurement solution is 2% aqueous solution, the formula is: V=Kdt. V represents the viscosity, the unit is mPa.s, K is the constant of the viscometer, d represents the density at constant temperature, t refers to the time from top to bottom through the viscometer, the unit is second s. This method is relatively cumbersome to operate, and if there are insoluble substances, it is easy to cause errors, and it is difficult to identify the quality of hydroxypropyl methylcellulose.

Rotational viscometer is generally used to measure its viscosity now, and the NDJ-1 type viscometer is generally used in China, and its formula is η=Kα. η represents the viscosity, and the unit is also mPa.s, K is the coefficient of the viscometer, and α is the reading of the viscometer pointer.

The detection method of 2% viscosity of hydroxypropyl methylcellulose:

1. This method is suitable for determining the dynamic viscosity of non-Newtonian fluids (solutions, suspensions, emulsion dispersion liquids or surfactant solutions, etc.) of high polymers.

2. Instruments and Utensils

1 Rotary viscometer (the Chinese Pharmacopoeia stipulates the use of NDJ-1 and NDJ-4 types)

2 constant temperature water bath constant temperature accuracy ± 0.10C

3 The thermometer scale is 0.20C, and it has been verified periodically.

4 Frequency meter Viscometer (such as NDJ-1 type, NDJ-4 type) using frequency stabilization measures must be used as a backup. Accuracy 1%a

3. Operation method Accurately weigh 8.0g sample, put it into a dry, tared 400mL tall beaker, add about 100mL of 80-90℃ hot water, stir for 10min to disperse evenly, add cold water under stirring To a total of 400mL. At the same time, keep stirring for about 30 minutes to make a 2% (w/w) solution, put it in the refrigerator and cool it in an ice bath until the surface is thinly iced, take it out and put it in a constant temperature tank to keep the central temperature at 20 ± 0.1 degrees for detection salary.

1 The installation and operation of the instrument shall be carried out according to the instruction manual of the instrument, and the appropriate rotor and speed shall be selected according to the viscosity range of the test product and the provisions of the Pharmacopoeia under the text of the product.

2 Adjust the constant temperature water temperature according to the determination under each drug item.

3 Take the test sample and place it in the container specified by the instrument, and after constant temperature for 30 minutes, measure the deflection angle (a) according to the law. Turn off the motor, and then turn it on again to make a measurement. The difference between each measured value and the average value shall not exceed ±3% of the average value, otherwise a third measurement should be performed.

4 Take the average value of 2 measurements and calculate according to the formula to obtain the dynamic viscosity of the test product.

4. Record and calculation

1. Record the type of rotary viscometer, the number and speed of the rotor used, the constant of the viscometer ((K’ value), the measured temperature, and the value measured each time.

2 calculation formula

Dynamic viscosity (MPa”s)=Ka where K is the viscometer constant a measured with a standard liquid of known viscosity is the deflection angle

If you have any questions about HPMC, you can always consult me

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