Praktikum Farmasi Fisika:Viskositas dan Rheologi Sediaan Farmasi

Summary

In this practical video, Ibu Neneng introduces a session on viscosity and rheology in physical pharmacy. The focus is on testing the viscosity of two types of liquids: paraffin (a Newtonian fluid) and an emulsified pharmaceutical solution (a non-Newtonian fluid). Using a Brookfield viscometer, the experiment demonstrates how viscosity changes with varying shear rates for the non-Newtonian fluid while remaining stable for the Newtonian fluid. Key learning points include the importance of selecting the correct spindle, understanding the flow behavior of liquids, and the impact of temperature, shear rate, and time on non-Newtonian fluids in pharmaceutical formulations.

Takeaways

• 😀 Viscosity refers to the resistance or opposition of a fluid to flow, while rheology is the study of the flow properties of fluids.
• 😀 The experiment involves testing two types of liquids: paraffin (a Newtonian fluid) and a pharmaceutical emulsion (a non-Newtonian fluid).
• 😀 The Brookfield viscometer is used to measure the viscosity of both liquids and analyze their rheological properties.
• 😀 It is important to select the correct spindle for each liquid when using the viscometer to ensure accurate measurements.
• 😀 For paraffin, the viscosity remains stable (20-21 centipoise) despite changes in the rotational speed (RPM), which is characteristic of Newtonian fluids.
• 😀 The viscosity of the pharmaceutical emulsion changes with varying RPM, indicating that it is a non-Newtonian fluid with shear rate-dependent viscosity.
• 😀 Non-Newtonian fluids, like the emulsion, are significantly affected by temperature, shear rate, and time.
• 😀 Most pharmaceutical formulations are non-Newtonian, with a preference for thixotropic flow behavior, which means the viscosity decreases under shear and returns to normal when rested.
• 😀 The experiment demonstrates that for non-Newtonian fluids, the flow behavior is not linear with respect to shear rate.
• 😀 Understanding viscosity and rheology is essential for pharmaceutical sciences, as most medicines are non-Newtonian and must be designed to have stable and predictable flow properties.
• 😀 In pharmaceutical formulations, maintaining thixotropic behavior ensures that the consistency of the product remains stable over time and upon usage.

Q & A

What is viscosity, and why is it important in this experiment?

Viscosity is the resistance or obstruction of a fluid to flow. It is important in this experiment because it helps in understanding how different fluids behave when subjected to stress or force, which is crucial in various pharmaceutical formulations.

What is rheology, and how does it relate to viscosity?

Rheology is the study of the flow and deformation of materials, particularly liquids. It is closely related to viscosity because rheology analyzes how fluids flow under different conditions, including the viscosity changes in response to stress or shear rates.

What types of fluids are being tested in this experiment?

Two types of fluids are being tested: paraffin, which is considered a Newtonian fluid, and a pharmaceutical emulsion, which is a non-Newtonian fluid.

What equipment is used to measure the viscosity in this experiment?

A Brookfield viscometer is used to measure the viscosity of both fluids. This device allows precise measurement of viscosity by determining the resistance to flow as the fluid is rotated.

How do you determine the appropriate spindle to use with the Brookfield viscometer?

The appropriate spindle is determined by checking the compatibility of the spindle with the fluid being tested. For paraffin, spindle 61 is used, and for the pharmaceutical emulsion, spindle 63 is appropriate.

Why is the selection of the correct spindle crucial for accurate viscosity testing?

The correct spindle ensures that the viscosity measurements are accurate and reliable. Using the wrong spindle can lead to incorrect results, as each spindle is designed to interact with the fluid in specific ways based on its viscosity.

What happens to the viscosity of paraffin when the speed of the viscometer is changed?

The viscosity of paraffin remains constant, around 20-21 centipoise, regardless of the change in the speed (RPM). This behavior is characteristic of Newtonian fluids, where viscosity does not change with shear rate.

What happens to the viscosity of the pharmaceutical emulsion when the speed is changed?

The viscosity of the pharmaceutical emulsion changes when the speed (RPM) is altered. This indicates that the fluid is non-Newtonian, meaning its viscosity is dependent on the shear rate.

What is the significance of understanding whether a fluid is Newtonian or non-Newtonian in pharmaceutical formulations?

Understanding whether a fluid is Newtonian or non-Newtonian is crucial in pharmaceutical formulations because it helps predict how the substance will behave under different conditions, such as during storage or application. Non-Newtonian fluids, like emulsions, often have more complex behaviors, which must be considered in formulation stability and effectiveness.

What is a thixotropic fluid, and why is it relevant to pharmaceutical formulations?

A thixotropic fluid is a type of non-Newtonian fluid whose viscosity decreases over time when subjected to shear stress (such as shaking) and returns to its original viscosity once the stress is removed. This is important for pharmaceutical formulations as it ensures that the product remains stable and easy to apply after being disturbed, such as in emulsions or suspensions.