Rheological behaviour of pharmaceutical fluids

Characteristics for the rheological behaviour of pharmaceutical fluids

The first experiment showed an increase in viscosity and therefore a decrease in shear rate,as a result of increasing the concentration of the tested sample.

The second experiment showed a decrease in viscosity and therefore an increase in shear rate, by increasing the temperature of the tested sample .

From the third experiment showed that the shear rate of the tested sample increases as the applied stress caused by the rotation speed of the Brookfield viscometer is increased thus effectively decreasing its viscosity.(pharmacy,D,2010)

Keywords in this experiment :

Hydrocolloids ,Hysteresis loop , Shear rate, Non - Newtonian Fluids, Pseudoplasticity , Thixotropy and Shear rate.

Hydrocolloids in this experiment are used mainly as suspending agents ,so understanding their rheological properties will allow appropriate adjustments to be made to ensure that the products are easily administered (e.g. either to be poured from a bottle or squeezed through a syringe), sedimentation is either prevented or retarded and for the product to be suitably presented(Marriott,2007)

The materials were used and the experiment has done as described in the practical booklet without any major changes from the method.

Experiment 1 results :

* Solutions were tested:1%, 2% and 4% Methylcellulose

* Equipments: Rhometer (ASTM Spindle No.2), laboratory jack, beaker

Concentration (%)

1%

2%

4%

Viscosity (cP)

6.9

16.5

76.5

According to the results, as the concentration of solution increase, viscosity increase. so concentration had major effect on flow behaviour of solution. At 4% the viscosity was more than four times of that at the 2% solution.wherease at 2% the viscosity was more than double that of the 1% solution. This shows rapid increase in viscosity as the concentration is doubled. Also as the number of intermolecular forces increases, therefore the flow rate decreases, as the spindle needs more energy to rotate.

The parameters which affect the accuracy of the data: Present of bubbles in the solution, , the calibration viscometer and the spindle wasn't washed, dried and cleaned (e.g. making them higher than expected)

Experiment 2 results :

Solution were tested: 1% PVP

Equipments: Ostwald viscometer

Water bath temp.

Flow time 1 (sec)

Flow time 2 (sec)

Mean flow time (sec)

25ºC (room temp.)

242

246

244

40ºC

170

167

168.5

According to results,at low temperature,time depence and consistency was higher. Experience was more vibrated as increasing the temperature indicates,decreasing in viscosity, the atoms in the liquid accumulate more energy. Which means that the intermolecular forces within the sample become more flexible(decrease), therefore increasing its flow rate caused decreasing its viscosity. Air bubbles, Suck the solution below the viscometer line

and Temperature fluctuations cause any contradiction showed during this practical.

Experiment 3 results :

Solution: Tragacanth 0.8%

Equipment: beaker, Rhometer (ASTM Spindle No.2), beaker

Rotation speed (rpm)

Up ramp

2

5

10

20

50

Revolutions/ sec (rpm/60)

Up ramp

0.033

0.083

0.167

0.333

0.833

Viscosity (mPa.sec/ cP)

359.9

293.9

186.0

201.0

156.0

Rotation speed (rpm)

Down ramp

2

5

10

20

50

Revolutions/ sec (rpm/60)

Down ramp

0.033

0.083

0.167

0.333

0.833

Viscosity (mPa.sec/ cP)

151.8

186.0

210.0

245.9

284.9

The sample tested shows non-Newtonian behaviour, in both the up-ramp and the down ramp viscosities, by increasing the shear rate, viscosity decreases. The graph revealed that the down ramp values displace the up ramp values showing a hysteresis loop. A time dependant decrease in viscosity is seen, as the thixotropic (macromolecules) do not mutate quiqly to the decreasing shear rates. Because of the fact that as shear stress is applied ,the macromolecules in tragacanth can use intermolecular bonds to form a three dimensional , which is crushed as shear stress is appeared (Marriott, 2007).

An error was shown at 10 rpm due topossible following :accuracyand adjusting the rheometer, incorrect handling of the equipment or various inconsistencies in the calibration of the machine.

Rheogram

Viscosity vs. rotation speed

According to the above experiments, the temperature, concentration and shear rate has significant effect on rheological properties of solution. By increasing the shear stress on non-Newtonians solutions, the shear rate increased. Also, by increasing the concentration, the shear rate decreased. In addition, by increasing the temperature, the shear rate increased.

Bibliography

Marriott, C. (2007). Non-Newtonian Fluids. In M. E. Aulton, & M. E. Aulton (Ed.), Pharmaceutics: The design and manufacture of medicies (3rd Edition ed., pp. 49-57). Churchill Livingstone.

Pharmacy, D. o. (2010). Experimental Booklet: Pharmaceutics. PY1070B & PY2390B Pharmaceutics practical guide .

Please be aware that the free essay that you were just reading was not written by us. This essay, and all of the others available to view on the website, were provided to us by students in exchange for services that we offer. This relationship helps our students to get an even better deal while also contributing to the biggest free essay resource in the UK!