Rheology and Dynamic Viscosity Quiz

The science that studies how materials deform and flow under stress and strain.

A test that measures a fluid's resistance to flow.

Rheological measurements help classify and characterize materials, providing insights into viscosity (thickness), elasticity (stretchability), and viscoelasticity (combination of both).

Rheology is essential for understanding how materials behave during processing and how they perform in their final applications.

Rheological measurements help ensure the quality and consistency of finished products, reducing manufacturing variations and improving product performance.

Rheology can indicate the presence of contaminants, poor mixing, or other issues that can affect product quality.

Rheology plays a crucial role in designing optimal processing conditions for various materials, ensuring efficiency and quality.

By understanding the rheological behavior of materials, engineers and scientists can choose the most suitable processing methods for desired product characteristics.

The force applied parallel to a surface divided by the area of the surface. It measures the force per unit area that causes deformation.

The ratio of the displacement of a layer to its distance from the fixed layer. It measures the amount of deformation caused by shear stress.

The rate of change of shear strain. It measures how quickly the deformation is happening.

The ratio of shear stress to shear strain rate. It measures the fluid's resistance to flow.

A type of viscometry that measures viscosity by applying a known force to a rotating object and measuring the resulting angular velocity.

A type of viscometry that measures viscosity by measuring the flow rate of a fluid through a capillary tube.

A type of viscometry that measures viscosity by measuring the time it takes for a known volume of fluid to fall through a narrow tube.

A measure of a fluid's resistance to flow. Higher viscosity means the fluid flows slower. It's measured in Pascal-seconds (Pa·s) or Poise (P).

A fluid's resistance to flow is directly proportional to the shear rate. Doubling the shear rate doubles the resistance.

A type of viscometer where a fluid flows through a tube under the influence of gravity. The flow time is measured to determine viscosity.

A measure of a material's resistance to deformation under stress. It reflects how stiff or flexible the material is.

Describes a material's ability to deform when subjected to a constant stress. It reflects how well the material can flow or creep.

A property of materials that exhibit both viscous and elastic behavior. It combines the characteristics of solids and liquids.

A rule that relates the complex viscosity of a material to its frequency-dependent storage and loss moduli.

A mathematical model that describes the behavior of viscoelastic materials under stress. It involves complex moduli that represent both elastic and viscous components.

The tendency of a fluid to decrease in viscosity over time under constant shear stress.

Fluids that have a constant viscosity regardless of the applied shear stress.

The rate at which a fluid is deformed under shear stress.

The relationship between shear stress and shear rate.

The temperature at which a substance transitions from a solid to a liquid.

Viscosity increases with increasing pressure.

Materials that exhibit both elastic and viscous behavior. They can deform under stress and return to their original shape but also flow over time.

The point at which a material starts to flow when subjected to increasing shear stress. This is the threshold beyond which the material behaves like a liquid.

The angle between the stress and strain in a material under applied force. For purely elastic materials, this angle is 0 degrees.

A material's response to stress and strain can change depending on how quickly the stress is applied. This is a key factor in understanding material behavior in various applications.

A process where two or more dry powder components are mixed to achieve uniform distribution of each component throughout the mixture. This ensures every particle of one component is as close as possible to a particle of every other component.

A type of powder mixing where no liquid is added during the process. The powders are mixed in their dry state.

A type of powder mixing where a liquid binder is added to the powder mixture. This leads to the formation of granules, improving flowability and handling properties.

A type of powder mixing used for mixtures where the active ingredient (drug) is present at low concentrations (less than 5% by weight). The mixing process is often followed by deagglomeration using a sieve to ensure fine and homogeneous distribution.

This mixing occurs after the main powder mixture is prepared and involves adding additional components like lubricants or glidants to improve processing properties. It usually involves short mixing times (3-5 minutes).

A type of powder mixer where particles tumble over each other due to rotation, promoting good mixing.

A type of powder mixer with a fixed vessel and an internal impeller that moves powder groups, reducing fine particle segregation.

A powder mixer with a rotating impeller that creates centrifugal forces, increasing energy input and breaking aggregates. Used after convective or tumbling mixing.

A type of powder mixer where powder is subjected to a flowing gas stream, allowing particles to float and enhancing mobility.

A disadvantage of Y-cone mixers. Larger particles tend to settle at the bottom, leading to uneven mixing.

A potential problem with convective mixers. Areas in the mixer where powder movement is minimal, resulting in uneven mixing.

A risk with impaction & high shear mixers. Excessive force can break powder particles, impacting their size and properties.

A benefit of using fluidised bed mixers. The flowing gas stream reduces the risk of powder sticking to mixer surfaces.

The process where individual particles in a powder mix move randomly, contributing to a more homogeneous blend.

The movement of groups of particles in a powder mixture, creating larger-scale mixing.

Layers of particles in a powder mixture slide over each other, causing mixing due to this relative motion.

The tendency for particles of different sizes, shapes, or densities to separate during mixing.

The ratio of the volume of powder to the volume of the mixing vessel. This affects how well the powder can move and mix.

A type of mixer where powder tumbles and mixes due to gravity and the movement of the vessel.

The movement of individual particles due to random motion, usually in gases or liquids.

The movement of groups of particles, often driven by temperature differences. Think of hot air rising.

The movement of particles by sliding over each other along specific planes within a material.

A mixture where each particle of one component is surrounded by particles of the other component, essentially the ideal mix.

A mixture with a random distribution of particles, where the chance of finding a specific component is equal throughout the mixture.

The tendency for components in a powder mixture to separate based on differences in properties like size, density, or shape.

A powder formulation method where small particles are bonded together to form larger particles, improving flow properties and reducing segregation.

Mixers that use high shear forces to break down cohesive particles and distribute them evenly, suitable for very cohesive powders.

Large particles of the drug lead to uneven distribution throughout the powder mixture, resulting in inconsistent dosing.

Reducing the size of drug particles improves their distribution in the mixture, ensuring greater homogeneity in the final product.

Agglomeration of particles (clumps) creates uneven distribution, making it difficult to achieve a uniform mix.

Electrostatic charging can make powders cling together and become difficult to mix. Using materials that minimize surface contact can help reduce this effect.

Powder handling during mixing should be efficient, minimizing transfers and vibrations. This helps maintain uniformity and prevent segregation.