| Popis: |
Rheology is the study of how materials deform and flow as a result of an external force, and is one tool that is used by formulators to help characterize semisolid dosage forms. The two extremes of rheological behavior are elastic and viscous (or plastic) behavior. Between elastic and viscous behavior lies the real world of most substances, which are viscoelastic materials. In the case of viscoelastic materials, timescales are important to rheological behavior—when deformation is fast, materials exhibit solid-like behavior; when deformation is slow, materials exhibit fluid-like behavior. The rheology of semisolid formulations provides critical information for product and process performance, including product stability. Rheology-based measurements can help predict which formulations might exhibit flocculation, coagulation, or coalescence, resulting in undesired effects such as settling, creaming, or separation. Viscosity is a measure of the resistance of a material to flow, and is just one aspect of the rheological profile of a formulation. |
