Let’s talk about hydroxypropyl methyl cellulose HPMC and how to measure its viscosity. The viscosity here refers to the apparent viscosity, which is an important reference to hydroxypropyl methyl cellulose.
Standard. The usual measurement methods are rotational viscosity measurement, capillary viscosity measurement and fall viscosity measurement. The determination method of hydroxypropyl methyl cellulose was capillary adhesion.
The method of degree determination, using the Uchs viscometer. Usually the determination of the solution is 2% aqueous solution, the formula is: V=Kdt. V is the viscosity in mpa. s and K is the viscometer constant.
D is the density at constant temperature and T is the time from top to bottom through the viscometer in seconds. This way of operation is more cumbersome, if there is insoluble matter.
Words are easy to cause errors, it is difficult to identify the quality of hydroxypropyl methyl cellulose. Now it is commonly used to measure the viscosity of the rotary viscometer, the general use in China .
The formula of the NDJ-1 viscometer is η=Kα. η is the viscosity, also in mpa. s, K is the coefficient of the viscometer, and α is the reading of the viscometer pointer.
Hydroxypropyl methyl cellulose 2% viscosity test method:
1, this method is suitable for the determination of the dynamic viscosity of non-Newtonian fluids (a polymer solution, suspension, emulsion dispersion liquid or surfactant solution, etc.).
2. Instruments and appliances
2.1 Rotary viscometer (NdJ-1 and NDJ-4 are required by Chinese Pharmacopoeia)
2.2 Constant temperature water bath constant temperature accuracy 0.10C
2.3 The temperature scoring degree is 0.20C, which is periodically verified.
2.4 Frequency meter Viscometers using frequency stabilization measures (such as NDJ-1 and NDJ-4) shall be reserved. Accuracy of 1%. A
8. Og sample was accurately weighed and put into a dry, toned 400mL tall beaker. Add about 100mL of 80-90 degree hot water and stir for 10min to separate
Evenly disperse, stir and add cold water to 400mL in total. Meanwhile, stir continuously for 30min to make a 2% (W/W) solution, and put it into the refrigerator for ice bath to cool until it forms thin ice on the surface.
Take out and put into the constant temperature tank to keep the central temperature to 20 ℃ 0.1 ℃.
3.1 The installation and operation of the instrument shall be carried out in accordance with the operating instructions of the instrument, and the appropriate rotor and rotor shall be selected according to the viscosity range of the tested product and the provisions of pharmacopoeia under the text of the product
Rotational speed.
3.2 Adjust the constant temperature water temperature according to the determination under each drug item.
3.3 The test product was placed in the container specified by the instrument, and the deflection Angle (a) was measured according to law after 30 minutes of constant temperature. Turn off the motor and restart it for determination once more
The difference between the mean values should not exceed 3%, otherwise a third measurement should be made.
3.4 Calculate the mean value of the two tests according to the formula to obtain the dynamic viscosity of the tested product.
4. Record and calculate
4.1 Record the rotary viscometer model, rotor number and speed used, viscometer constant (K ‘value), measured temperature, and each measurement. Value.
The calculating formula of 4.2
Dynamic viscosity (MPa”s)=Ka where K is the viscometer constant measured with a standard liquid of known viscosity and A is the deflection Angle
Post time: Apr-25-2024