Rheology in Pharmacy

Rheology

• Rheology is the science that deals with the flow and deformation of materials under the influence of stress, derived from the Greek words "rheo" (flow) and "logos" (science).

Importance of Rheology in Pharmacy

• Rheology is important in pharmacy, particularly in the development and production of liquid dosage forms.

Viscosity

• Viscosity is the property of a fluid that offers resistance to the movement of one layer of fluid over an adjacent layer, denoted by Tau (τ).
• Viscosity is a measure of a fluid's thickness or resistance to flow.

Newtonian Laws

• Newton's law of viscous flow states that the shear rate of a fluid is directly proportional to the shear stress.
• Newtonian systems are fluids that obey the Newtonian law of viscous flow, exhibiting a linear stress-rate of shear curve that passes through the origin.

Thixotropy

• Thixotropy is a type of time-dependent non-Newtonian behavior where the viscosity of a fluid decreases over time when subjected to a constant shear rate, and returns to its original viscosity when the shear rate is removed.

Determination of Viscosity

• Viscosity can be determined by plotting the shear rate against the shear stress, resulting in a rheogram.

Factors Affecting Rheological Properties

• Factors such as temperature, concentration, and particle size can affect the rheological properties of materials.

Pharmaceutical Applications of Rheology

• Rheology is important in the development and production of various fluid pharmaceutical products, such as syrups, suspensions, and emulsions, which exhibit different rheological behaviors.
• Examples of fluid pharmaceutical products exhibiting various rheological behaviors include water, chloroform, castor oil, and syrup.

This quiz covers the definition and importance of rheology in pharmacy, including its application, viscosity, Newtonian laws, thixotropy, and pharmaceutical applications. Students will be able to define rheology and understand Newton's law of flow.