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RHEOLOGY-1

RHEOLOGY-1

PHARMAROCKS
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RHEOLOGY-1

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  1. RHEOLOGY PART-1 • RHEOLOGY DEFINATION • FUNDAMENTALS OF RHEOLOGY • IMPORTANCE OF RHEOLOGY • VISCOSITY • KINEMATIC VISCOSITY • FLUIDITY

  2. RHEOLOGY Rheology is the science which deals with flow of liquid and deformation of solid.

  3. RHEOLOGY Rheology is a Greek word Rheo Means “Flow” & Logia, “study of” THUS RHEOLOGY MEANS STUDY OF FLOW Rheology is the science/physics that concerns with the flow of liquids and the deformation of solids.

  4. RHEOLOGY Study of flow properties of liquids is important for pharmacist working in the manufacture of several dosage forms, simple liquids, gels, ointments, creams, and pastes. These systems change their flow behavior when exposed to different stress conditions.

  5. Fundamentals of Rheology 1. Manufacturing of dosage forms: Materials undergo process such as mixing, flowing through pipes, filling into the containers etc. Flow related changes influence the selection of mixing equipment.

  6. Fundamentals of Rheology 2. Handling of drugs for administration: The syringibility of the medicines, the pouring of the liquids from containers, extrusion of ointment from tubes, all depend on the changes in flow behavior of dosage forms.

  7. IMPORTANCE OF RHEOLOGY Formulation of medicinal and cosmetic creams, pastes and lotions. Formulation of emulsions, suspensions, suppositories, and tablet coating. Fluidity of solutions for injection. Extrusion of a paste from a tube

  8. IMPORTANCE OF RHEOLOGY In mixing and flow of materials, their packaging into the containers, their removal prior to use, the pouring from the bottle. Passage of the liquid to a syringe needle. Influence the choice of processing equipments in the pharmaceutical system.

  9. IMPORTANCE OF RHEOLOGY RHEOLOGY can affect the Patient’s acceptability of the product Physical stability Biologic availability Absorption rate of drugs in the gastrointestinal tract.

  10. VISCOSITY It is defined as resistance to the flow ηis the coefficient of viscosity and is calculated as η = F/ G Where F= Shearing stress G= Rate of shear Unit of viscosity Poise or dyne.sec/cm2.

  11. VISCOSITY The most common unit of viscosity is the dyne second per square centimeter [dyne s/cm2], which is given the name poise [P] after the French physiologist Jean Poiseuille (1799–1869). Ten poise equal one pascal second [Pa s] making the centipoise [cP] millipascal second [mPas] identical. Jean Poiseuille

  12. VISCOSITY According to Arrhenius equation the viscosity of solution decreases with increase in temperature EXCEPTMethyl cellulose because here viscosity increase with the increase in temperature Viscosity is measured using Viscometer OSWALD VISCOMETER

  13. VISCOSITY OSWALD VISCOMETER

  14. KINEMATIC VISCOSITY Kinematic viscosity is a measure of a fluid's internal resistance to flow under gravitational forces. Viscosity can be measured and reported as dynamic (absolute) viscosity or as kinematic viscosity. Dynamic viscosity is measure of fluid's resistance to shear flow when some external force is applied

  15. KINEMATIC VISCOSITY Kinematic viscosity is ratio of dynamic viscosity to density of that fluid. It is measure of fluid's resistance to shear flow under the weight of gravity V = μ / ρ Units: m2/s [Stock (s) or centistock (cs)] V= Kinetic viscosity μ = dynamic viscosity ρ = density of fluid V for Water = 1.14x10-6 m2/s & Air = 1.46x10-5 m2/s;

  16. EFFECT OF TEMPERATURE In general, viscosity of liquids decrease with increase in temperature whereas viscosity of gasesincrease with in increase temperature.

  17. IMPORTANT TERMS Shear: is the movement of material relative to parallel layer. Shear stress (F’): is the force per unit area required to bring about flow (F/A) Shear rate (S) difference in velocity dv, between two planes of liquids separated by distance dr (i.e. dv/dr) F/A αdv/dr

  18. Fluidity Fluidity; it is the reciprocal of viscosity Ø = 1/ η The ability of a substance to flow is called fluidity. The substances which show fluidity are called fluids. Liquid and gas are examples of fluids. The particles of liquid and gas are able to move freely because there is a large space between them

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