This document discusses rheology, which is the science of deformation and flow of matter under stress. It defines Newtonian and non-Newtonian systems, and their flow properties. Newtonian fluids obey Newton's law of viscosity, where viscosity is constant regardless of shear rate. Non-Newtonian fluids do not follow this law and can exhibit plastic, pseudoplastic or dilatant behaviors. Plastic fluids have a yield value and shear thinning fluids see decreasing viscosity with increasing shear rate. The document provides examples of pharmaceutical products that demonstrate different rheological behaviors and their structural causes. It emphasizes the importance of rheology in product development, manufacturing, and patient acceptability.
This document discusses complex fluids, which exhibit both liquid-like and solid-like properties. Complex fluids include polymeric solutions, gels, foams, and granular materials. They have heterogeneous structures with fluctuations across different length and time scales. When molecules in a polymeric solution or melt become sufficiently crosslinked, a gel transition occurs where a macroscopic cluster forms, localizing the molecules. The dynamics of particles in complex fluids are highly nonlinear and irregular, alternating between solid-like arrested states and fluid-like behavior depending on factors like density, temperature, and external forces inducing flow. While complex fluids are common in nature, their material properties are not fully understood and more research is still needed.
This document discusses rheology, which is the science of flow and deformation of materials. It defines rheology and explains its importance in pharmaceutical applications. It describes different types of flows including Newtonian, plastic, pseudoplastic and dilatant flows. It also discusses thixotropic behavior, instrumentation used to study rheology including viscometers, and applications of rheology in areas like creams, lotions and suspensions.
Rheology is the science that study flow of fluids. Viscosity is the main parameter of flow. Newtonian & non newtonian are the two types of flow behavior according to newtons law of flow. non-newtonian flow can be plastic, pseudoplastic, dilatant, thixotropic, antithixotropic or rheopexy. viscosity can be determined by using various viscometers such as capillary viscometer, cup & bob viscometer, cone & plate viscometer, falling sphere viscometer, brookfield viscometer, etc. factors affeting viscosity are intrinsic, extrinsic or temperature dependence.
The document discusses several factors that affect the viscosity of liquids. Viscosity refers to the stickiness or resistance to flow of a liquid. Key factors include flow conditions like laminar versus turbulent flow, shear rate, temperature, and pressure. Laminar flow results in lower viscosity than turbulent flow. Temperature and viscosity are inversely related, with higher temperatures resulting in lower viscosity. Pressure also affects viscosity, though not as significantly as temperature. The type of liquid, whether it is Newtonian or non-Newtonian, impacts how its viscosity responds to changes in factors like shear rate.
1. The document discusses different types of deformation that solids undergo when external forces are applied, including elastic deformation, plastic deformation, and breaking.
2. Elastic deformation is reversible and follows Hooke's Law, relating stress to strain linearly. Plastic deformation is irreversible and leads to a permanent change in shape.
3. The document also defines moduli that quantify a material's resistance to different types of deformation, including Young's modulus, shear modulus, and bulk modulus. These properties depend on the material and can be used to characterize its stiffness.
This theory is explain by Derjaguin , Landau , Verway , Overbeek So it is known as DLVO Theory.
According to this theory , The forces on colloidal particles in a dispersion medium are due to –
1. Electrostatic Repulsion
2. London type Vander Waals Attraction
This document discusses an introduction to rheology and its importance in pharmacy. It begins by outlining the topics to be covered, which include the importance of rheology in pharmacy applications, definitions and fundamentals, types of fluids, viscosity, measurements of viscosity, instrumentation, and viscoelasticity. The first section defines rheology and describes its importance in areas like manufacturing dosage forms, handling drugs for administration, topical applications, and more. The introduction provides definitions of key terms like shear stress and rate of shear. It also describes Newton's laws of viscous flow. The document goes on to classify fluids as Newtonian or non-Newtonian and describes different types of non-Newtonian fluids.
This document discusses complex fluids, which exhibit both liquid-like and solid-like properties. Complex fluids include polymeric solutions, gels, foams, and granular materials. They have heterogeneous structures with fluctuations across different length and time scales. When molecules in a polymeric solution or melt become sufficiently crosslinked, a gel transition occurs where a macroscopic cluster forms, localizing the molecules. The dynamics of particles in complex fluids are highly nonlinear and irregular, alternating between solid-like arrested states and fluid-like behavior depending on factors like density, temperature, and external forces inducing flow. While complex fluids are common in nature, their material properties are not fully understood and more research is still needed.
This document discusses rheology, which is the science of flow and deformation of materials. It defines rheology and explains its importance in pharmaceutical applications. It describes different types of flows including Newtonian, plastic, pseudoplastic and dilatant flows. It also discusses thixotropic behavior, instrumentation used to study rheology including viscometers, and applications of rheology in areas like creams, lotions and suspensions.
Rheology is the science that study flow of fluids. Viscosity is the main parameter of flow. Newtonian & non newtonian are the two types of flow behavior according to newtons law of flow. non-newtonian flow can be plastic, pseudoplastic, dilatant, thixotropic, antithixotropic or rheopexy. viscosity can be determined by using various viscometers such as capillary viscometer, cup & bob viscometer, cone & plate viscometer, falling sphere viscometer, brookfield viscometer, etc. factors affeting viscosity are intrinsic, extrinsic or temperature dependence.
The document discusses several factors that affect the viscosity of liquids. Viscosity refers to the stickiness or resistance to flow of a liquid. Key factors include flow conditions like laminar versus turbulent flow, shear rate, temperature, and pressure. Laminar flow results in lower viscosity than turbulent flow. Temperature and viscosity are inversely related, with higher temperatures resulting in lower viscosity. Pressure also affects viscosity, though not as significantly as temperature. The type of liquid, whether it is Newtonian or non-Newtonian, impacts how its viscosity responds to changes in factors like shear rate.
1. The document discusses different types of deformation that solids undergo when external forces are applied, including elastic deformation, plastic deformation, and breaking.
2. Elastic deformation is reversible and follows Hooke's Law, relating stress to strain linearly. Plastic deformation is irreversible and leads to a permanent change in shape.
3. The document also defines moduli that quantify a material's resistance to different types of deformation, including Young's modulus, shear modulus, and bulk modulus. These properties depend on the material and can be used to characterize its stiffness.
This theory is explain by Derjaguin , Landau , Verway , Overbeek So it is known as DLVO Theory.
According to this theory , The forces on colloidal particles in a dispersion medium are due to –
1. Electrostatic Repulsion
2. London type Vander Waals Attraction
This document discusses an introduction to rheology and its importance in pharmacy. It begins by outlining the topics to be covered, which include the importance of rheology in pharmacy applications, definitions and fundamentals, types of fluids, viscosity, measurements of viscosity, instrumentation, and viscoelasticity. The first section defines rheology and describes its importance in areas like manufacturing dosage forms, handling drugs for administration, topical applications, and more. The introduction provides definitions of key terms like shear stress and rate of shear. It also describes Newton's laws of viscous flow. The document goes on to classify fluids as Newtonian or non-Newtonian and describes different types of non-Newtonian fluids.
This document provides an overview of rheology and its importance in pharmaceutical applications. It begins with definitions of rheology as the study of flow and deformation of matter under stress. The importance of rheology in formulation of various dosage forms like creams, emulsions, and suspensions is discussed. The document then covers key concepts in rheology including Newton's laws of viscosity, different types of fluid flow (Newtonian, plastic, pseudoplastic, dilatant), and measurement of viscosity. Pharmaceutical examples are provided to illustrate different flow properties and their significance.
Rheology is the study of deformation and flow of matter. It governs the flow of fluids in the body like blood, lymph, and mucus. From a rheological perspective, materials are solids, liquids, or gases depending on whether their shape and volume remain constant under forces. The flow properties of materials determine how easily substances like emulsions and ointments can be processed and used. Materials can exhibit Newtonian or non-Newtonian flow based on whether their viscosity changes with applied stress. Key non-Newtonian flows include plastic, pseudoplastic, and dilatant. Factors like polymer structure, hydration, pH, and temperature affect the rheological properties of pharmaceutical products.
This document discusses rheology, which is the science describing the flow and deformation of matter under stress. It defines key terms like viscosity, shear stress, shear rate, and classifies fluids as Newtonian or non-Newtonian based on their relationship between shear stress and shear rate. Newtonian fluids have a constant viscosity regardless of shear rate, while non-Newtonian fluids have variable viscosity. Plastic, pseudoplastic, and dilatant behaviors are described for non-Newtonian fluids. Thixotropy, which is a time-dependent decrease and recovery of viscosity under shear, is also discussed. The document concludes by explaining the operation and calibration of common viscometers.
This document discusses Newtonian and non-Newtonian flow. It begins by introducing rheology and the importance of understanding flow properties for pharmaceutical dosage forms. It then defines Newtonian flow as obeying Newton's law of viscosity and provides examples. Non-Newtonian flow is defined as not following this law and described as existing in three types: plastic, pseudoplastic, and dilatant flow. Examples are given for each type of non-Newtonian flow. Rheograms illustrating different fluid behaviors are also included.
This document discusses surface and interfacial phenomena. It defines interfaces and divides them into solid and liquid interfaces. Liquid interfaces deal with liquid-gas or liquid-liquid phases and have applications in infiltration, biopharmaceuticals, and suspensions/emulsions. Surface tension exists between solid-gas and liquid-gas phases, while interfacial tension exists between immiscible liquids. Various methods are described to measure surface tension, interfacial tension, and surface free energy. Surfactants are also discussed, including how they lower tensions and are used in products. Adsorption at interfaces and isotherms are briefly covered.
This document discusses kinetics and drug stability. It defines zero, first, second, and pseudo-first order reactions and methods for determining reaction order experimentally. Factors affecting reaction rate and kinetics of solid state reactions are also covered. The document discusses predicting shelf-life using the Arrhenius equation from accelerated stability testing. It outlines appropriate storage methods for pharmaceutical products and concludes by distinguishing between kinetics, which involves reaction rates, and thermodynamics, which involves energy transformations.
Sensitization and protective colloidal actionVarshaBarethiya
Lyophobic dispersions are unstable in the presence of electrolytes due to the neutralization of particle charges. Sensitization can occur when a small amount of hydrophilic colloid is added, making the hydrophobic sol more sensitive to precipitation from electrolytes through adsorption of oppositely charged particles. Protective colloidal action results from the adsorption of a large amount of hydrophilic colloids carrying opposite charges onto hydrophobic particles, forming a protective layer that prevents coagulation by ions. Colloids that stabilize other colloids through this process are called protective colloids.
1. The document discusses different types of complexes that can form between molecules, including metal ion complexes, organic molecular complexes, and inclusion complexes.
2. Metal ion complexes involve donation of electron pairs from ligands to a central metal ion. Important types include inorganic complexes containing ligands like ammonia, and chelate complexes where a ligand donates multiple electron pairs.
3. Organic molecular complexes are weaker and involve polarization of molecules and charge transfer rather than covalent bonding. Examples discussed include complexes of drugs containing N-C=S moieties that can complex with iodine.
1. An insoluble monomolecular film forms when a slightly soluble material is spread on a liquid surface, such as water. The molecules stand vertically and pack closely, with thickness equaling molecular length.
2. Film pressure is measured as the difference between the surface tension of the clean liquid and the surface tension of the liquid covered by the film. The film resists contraction of the clean surface.
3. A π-A curve plots the relationship between film pressure and film area, showing phase changes as the film is compressed, from a gas-like to liquid-like to solid-like state.
Physics of tablet compression, mechanism of tablet
formation, bonding in tablets, the effect of compressional force on tablet properties, effect
of lubricants on tablet compression, binding, instrumented tablet machines and tooling,
problems associated with large scale manufacturing of tablets.
SURFACE TENSION, INTERFACIAL TENSION, SURFACE FREE ENERGY, Measurement of surface and interfacial tension-capillary rise method, drop number method, drop weight method, Du Nuoy tensiometer method, Spreading of liquids, spreading coefficient, surface active agents, hydrophilic-lipophilic balance, soluble monolayers, Adsorption on solid surface, Isotherms
When phases exist together, the boundary between two of them is known as interface.
When the phase is in contact with atmosphere it is termed as surface.
The document discusses solubility of liquids in liquids through phase diagrams. It provides examples of complete miscibility (ethanol and water), complete immiscibility (water and mercury), and partial miscibility (water and phenol). Systems can show increasing, decreasing, or unchanged miscibility with temperature. Phase diagrams graph temperature vs. composition to illustrate these relationships. The document also discusses solid-liquid systems and eutectic points, where three phases (liquid, solid A, solid B) coexist at the lowest temperature with a single liquid phase.
1. Interfacial phenomena are important in pharmacy for drug adsorption, penetration through membranes, emulsion formation and stability, and suspension of insoluble particles.
2. Surface tension is the inward force at the liquid interface, while interfacial tension exists between immiscible liquids. Temperature, additives, and molecular interactions influence surface/interfacial tensions.
3. Several methods measure these tensions, including the capillary rise, Du Nouy ring, and drop weight methods. Surface-active agents are amphiphilic molecules that adsorb at interfaces and are used as wetting, solubilizing, and emulsifying agents in pharmaceutical formulations.
Coarse dispersions are heterogeneous systems where the dispersed particles are larger than 1000 nm. They are characterized by relatively fast sedimentation. The dispersed phase may be easily separated from the continuous phase by filtration. A pharmaceutical suspension is a coarse dispersion where the internal phase is uniformly dispersed throughout the external phase. The internal phase typically has particle sizes between 0.5-5 microns. Suspensions demonstrate properties like pseudoplasticity and thixotropy which influence stability during manufacture and storage.
This document provides an introduction to rheology and its relationship to fluid mechanics. It defines rheology as the science describing the flow and deformation of matter under stress. Rheology is relevant to fluids as all fluids flow and deform under stress. The document discusses different material types including elastic solids, plastic materials, and fluids. It describes concepts such as viscosity, shear stress, and normal stress. It also covers non-Newtonian fluids and how their viscosity can vary with applied stress or time. Different types of non-Newtonian fluids like shear-thinning, shear-thickening, Bingham plastics, and thixotropic fluids are defined. The document concludes with sections on viscoelastic behavior, different
The document discusses interfaces and surface/interfacial phenomena. It defines an interface as the boundary between two phases and notes that interfacial molecules have different properties than bulk molecules. It discusses different types of interfaces that can exist depending on whether the adjacent phases are solid, liquid, or gas. It then discusses several important interfacial phenomena in pharmacy, including drug adsorption, membrane penetration, emulsion formation/stability, and particle dispersion in liquids to form suspensions.
Diffusion phenomena, Drug release and dissolution
The document discusses key concepts related to diffusion including:
1. Diffusion is the movement of molecules from an area of high concentration to low concentration.
2. Fick's laws of diffusion describe the flux and rate of change of concentration over time for diffusing substances.
3. Membrane permeability and factors like thickness influence diffusion rates in drug delivery applications like transdermal patches.
This document discusses rheology and the importance of understanding flow properties in pharmaceutical manufacturing and product administration. It defines rheology as the study of flow and deformation of matter under stress. The document covers various types of fluid flow including Newtonian, plastic, pseudoplastic and dilatant. It also discusses thixotropy and measurement of viscosity using single point viscometers like Ostwald and falling sphere, as well as multi-point viscometers like cup and bob and cone and plate. Understanding rheology is important for developing dosage forms and ensuring their proper handling and administration.
SY - PP II - Rheology and Newtons Law of Flow.pdfKeval80
This document discusses rheology, which is the science of deformation and flow of matter. It defines key terms like viscosity, shear stress, and rate of shear. It explains Newton's law of flow and describes Newtonian and non-Newtonian systems. It also discusses factors that affect viscosity like temperature, thixotropy, and different types of viscosity. Finally, it describes common methods to measure and determine viscosity, such as capillary, falling ball, rotational, and other viscometers.
Rheology is the study of deformation and flow of matter. There are several types of rheological properties including stress, viscosity, viscoelastic modulus, creep, and relaxation times. Rheology is important in manufacturing pharmaceutical dosage forms and applications like ointments, syrups, suspensions, and emulsions where rheological properties influence acceptability, bioavailability, and handling. Materials can exhibit Newtonian, plastic, pseudo-plastic, or dilatant flow depending on the relationship between shear stress and shear rate. Viscometers are used to determine viscosity and classify fluids as Newtonian or non-Newtonian.
This document provides an overview of rheology and its importance in pharmaceutical applications. It begins with definitions of rheology as the study of flow and deformation of matter under stress. The importance of rheology in formulation of various dosage forms like creams, emulsions, and suspensions is discussed. The document then covers key concepts in rheology including Newton's laws of viscosity, different types of fluid flow (Newtonian, plastic, pseudoplastic, dilatant), and measurement of viscosity. Pharmaceutical examples are provided to illustrate different flow properties and their significance.
Rheology is the study of deformation and flow of matter. It governs the flow of fluids in the body like blood, lymph, and mucus. From a rheological perspective, materials are solids, liquids, or gases depending on whether their shape and volume remain constant under forces. The flow properties of materials determine how easily substances like emulsions and ointments can be processed and used. Materials can exhibit Newtonian or non-Newtonian flow based on whether their viscosity changes with applied stress. Key non-Newtonian flows include plastic, pseudoplastic, and dilatant. Factors like polymer structure, hydration, pH, and temperature affect the rheological properties of pharmaceutical products.
This document discusses rheology, which is the science describing the flow and deformation of matter under stress. It defines key terms like viscosity, shear stress, shear rate, and classifies fluids as Newtonian or non-Newtonian based on their relationship between shear stress and shear rate. Newtonian fluids have a constant viscosity regardless of shear rate, while non-Newtonian fluids have variable viscosity. Plastic, pseudoplastic, and dilatant behaviors are described for non-Newtonian fluids. Thixotropy, which is a time-dependent decrease and recovery of viscosity under shear, is also discussed. The document concludes by explaining the operation and calibration of common viscometers.
This document discusses Newtonian and non-Newtonian flow. It begins by introducing rheology and the importance of understanding flow properties for pharmaceutical dosage forms. It then defines Newtonian flow as obeying Newton's law of viscosity and provides examples. Non-Newtonian flow is defined as not following this law and described as existing in three types: plastic, pseudoplastic, and dilatant flow. Examples are given for each type of non-Newtonian flow. Rheograms illustrating different fluid behaviors are also included.
This document discusses surface and interfacial phenomena. It defines interfaces and divides them into solid and liquid interfaces. Liquid interfaces deal with liquid-gas or liquid-liquid phases and have applications in infiltration, biopharmaceuticals, and suspensions/emulsions. Surface tension exists between solid-gas and liquid-gas phases, while interfacial tension exists between immiscible liquids. Various methods are described to measure surface tension, interfacial tension, and surface free energy. Surfactants are also discussed, including how they lower tensions and are used in products. Adsorption at interfaces and isotherms are briefly covered.
This document discusses kinetics and drug stability. It defines zero, first, second, and pseudo-first order reactions and methods for determining reaction order experimentally. Factors affecting reaction rate and kinetics of solid state reactions are also covered. The document discusses predicting shelf-life using the Arrhenius equation from accelerated stability testing. It outlines appropriate storage methods for pharmaceutical products and concludes by distinguishing between kinetics, which involves reaction rates, and thermodynamics, which involves energy transformations.
Sensitization and protective colloidal actionVarshaBarethiya
Lyophobic dispersions are unstable in the presence of electrolytes due to the neutralization of particle charges. Sensitization can occur when a small amount of hydrophilic colloid is added, making the hydrophobic sol more sensitive to precipitation from electrolytes through adsorption of oppositely charged particles. Protective colloidal action results from the adsorption of a large amount of hydrophilic colloids carrying opposite charges onto hydrophobic particles, forming a protective layer that prevents coagulation by ions. Colloids that stabilize other colloids through this process are called protective colloids.
1. The document discusses different types of complexes that can form between molecules, including metal ion complexes, organic molecular complexes, and inclusion complexes.
2. Metal ion complexes involve donation of electron pairs from ligands to a central metal ion. Important types include inorganic complexes containing ligands like ammonia, and chelate complexes where a ligand donates multiple electron pairs.
3. Organic molecular complexes are weaker and involve polarization of molecules and charge transfer rather than covalent bonding. Examples discussed include complexes of drugs containing N-C=S moieties that can complex with iodine.
1. An insoluble monomolecular film forms when a slightly soluble material is spread on a liquid surface, such as water. The molecules stand vertically and pack closely, with thickness equaling molecular length.
2. Film pressure is measured as the difference between the surface tension of the clean liquid and the surface tension of the liquid covered by the film. The film resists contraction of the clean surface.
3. A π-A curve plots the relationship between film pressure and film area, showing phase changes as the film is compressed, from a gas-like to liquid-like to solid-like state.
Physics of tablet compression, mechanism of tablet
formation, bonding in tablets, the effect of compressional force on tablet properties, effect
of lubricants on tablet compression, binding, instrumented tablet machines and tooling,
problems associated with large scale manufacturing of tablets.
SURFACE TENSION, INTERFACIAL TENSION, SURFACE FREE ENERGY, Measurement of surface and interfacial tension-capillary rise method, drop number method, drop weight method, Du Nuoy tensiometer method, Spreading of liquids, spreading coefficient, surface active agents, hydrophilic-lipophilic balance, soluble monolayers, Adsorption on solid surface, Isotherms
When phases exist together, the boundary between two of them is known as interface.
When the phase is in contact with atmosphere it is termed as surface.
The document discusses solubility of liquids in liquids through phase diagrams. It provides examples of complete miscibility (ethanol and water), complete immiscibility (water and mercury), and partial miscibility (water and phenol). Systems can show increasing, decreasing, or unchanged miscibility with temperature. Phase diagrams graph temperature vs. composition to illustrate these relationships. The document also discusses solid-liquid systems and eutectic points, where three phases (liquid, solid A, solid B) coexist at the lowest temperature with a single liquid phase.
1. Interfacial phenomena are important in pharmacy for drug adsorption, penetration through membranes, emulsion formation and stability, and suspension of insoluble particles.
2. Surface tension is the inward force at the liquid interface, while interfacial tension exists between immiscible liquids. Temperature, additives, and molecular interactions influence surface/interfacial tensions.
3. Several methods measure these tensions, including the capillary rise, Du Nouy ring, and drop weight methods. Surface-active agents are amphiphilic molecules that adsorb at interfaces and are used as wetting, solubilizing, and emulsifying agents in pharmaceutical formulations.
Coarse dispersions are heterogeneous systems where the dispersed particles are larger than 1000 nm. They are characterized by relatively fast sedimentation. The dispersed phase may be easily separated from the continuous phase by filtration. A pharmaceutical suspension is a coarse dispersion where the internal phase is uniformly dispersed throughout the external phase. The internal phase typically has particle sizes between 0.5-5 microns. Suspensions demonstrate properties like pseudoplasticity and thixotropy which influence stability during manufacture and storage.
This document provides an introduction to rheology and its relationship to fluid mechanics. It defines rheology as the science describing the flow and deformation of matter under stress. Rheology is relevant to fluids as all fluids flow and deform under stress. The document discusses different material types including elastic solids, plastic materials, and fluids. It describes concepts such as viscosity, shear stress, and normal stress. It also covers non-Newtonian fluids and how their viscosity can vary with applied stress or time. Different types of non-Newtonian fluids like shear-thinning, shear-thickening, Bingham plastics, and thixotropic fluids are defined. The document concludes with sections on viscoelastic behavior, different
The document discusses interfaces and surface/interfacial phenomena. It defines an interface as the boundary between two phases and notes that interfacial molecules have different properties than bulk molecules. It discusses different types of interfaces that can exist depending on whether the adjacent phases are solid, liquid, or gas. It then discusses several important interfacial phenomena in pharmacy, including drug adsorption, membrane penetration, emulsion formation/stability, and particle dispersion in liquids to form suspensions.
Diffusion phenomena, Drug release and dissolution
The document discusses key concepts related to diffusion including:
1. Diffusion is the movement of molecules from an area of high concentration to low concentration.
2. Fick's laws of diffusion describe the flux and rate of change of concentration over time for diffusing substances.
3. Membrane permeability and factors like thickness influence diffusion rates in drug delivery applications like transdermal patches.
This document discusses rheology and the importance of understanding flow properties in pharmaceutical manufacturing and product administration. It defines rheology as the study of flow and deformation of matter under stress. The document covers various types of fluid flow including Newtonian, plastic, pseudoplastic and dilatant. It also discusses thixotropy and measurement of viscosity using single point viscometers like Ostwald and falling sphere, as well as multi-point viscometers like cup and bob and cone and plate. Understanding rheology is important for developing dosage forms and ensuring their proper handling and administration.
SY - PP II - Rheology and Newtons Law of Flow.pdfKeval80
This document discusses rheology, which is the science of deformation and flow of matter. It defines key terms like viscosity, shear stress, and rate of shear. It explains Newton's law of flow and describes Newtonian and non-Newtonian systems. It also discusses factors that affect viscosity like temperature, thixotropy, and different types of viscosity. Finally, it describes common methods to measure and determine viscosity, such as capillary, falling ball, rotational, and other viscometers.
Rheology is the study of deformation and flow of matter. There are several types of rheological properties including stress, viscosity, viscoelastic modulus, creep, and relaxation times. Rheology is important in manufacturing pharmaceutical dosage forms and applications like ointments, syrups, suspensions, and emulsions where rheological properties influence acceptability, bioavailability, and handling. Materials can exhibit Newtonian, plastic, pseudo-plastic, or dilatant flow depending on the relationship between shear stress and shear rate. Viscometers are used to determine viscosity and classify fluids as Newtonian or non-Newtonian.
This document provides an overview of rheology concepts including:
1. It defines rheology as the science concerned with the deformation of matter under stress.
2. It describes Newtonian and non-Newtonian fluids, explaining that Newtonian fluids have a constant viscosity while non-Newtonian fluids have variable viscosity.
3. It discusses the different types of non-Newtonian flow - plastic, pseudoplastic, and dilatant - and provides examples of materials that exhibit each type of flow.
This document provides an overview of rheology and key rheological concepts. It begins by defining rheology as the study of flow and deformation of materials under stress. It then discusses the importance of rheology for liquid pharmaceutical dosage forms. The document outlines the differences between Newtonian and non-Newtonian fluids, describing Newtonian fluids as having a constant viscosity regardless of stress, while non-Newtonian fluids have a variable viscosity. It provides examples of different types of non-Newtonian fluid flow, including plastic, pseudo-plastic, and dilatant flow. The objectives are to understand these rheological concepts and their significance for pharmaceutical products.
Rheology is the science of flow and deformation of matter. The document discusses rheology, defining it and explaining key concepts like viscosity, shear stress, shear rate, and different types of fluids. It also covers rheological flow models including the Newtonian, Bingham plastic, and power law models. Measurement techniques and common rheological instruments are briefly outlined.
IRJET- To Study the Fluid-Structure Interaction (FSI) Phenomenon of Non-Newto...IRJET Journal
1) The document discusses fluid-structure interaction between a non-Newtonian viscoelastic fluid and a flexible sheet.
2) Unlike Newtonian fluids, viscoelastic fluids can become unstable at very low Reynolds numbers due to elastic flow instabilities. These instabilities can drive oscillations in a flexible structure placed in the flow.
3) The study uses a wormlike micelle solution and a flexible rubber sheet to experimentally observe this interaction. High-speed video and particle tracking are used to characterize the oscillations of the flexible sheet induced by elastic instabilities in the fluid flow.
This document provides information about a fluid mechanics course taught by Dr. Muhammad Uzair at NED University of Engineering & Technology. The course objectives are to impart theoretical knowledge of fluid statics and dynamics and enable students to analyze and solve engineering problems. The course learning outcomes include being able to define fluid mechanics concepts, apply equations to solve problems, and analyze dimensional analysis and experimental work problems. The course will cover topics such as fluid properties, fluid statics, fluid dynamics, and dimensional analysis over its contents. Student learning will be assessed through exams, assignments, reports, and quizzes.
This document discusses an experimental investigation of different types of notches used to measure flow rate. Triangular and rectangular notches were tested to determine which provides more accurate measurements of discharge coefficient at varying flow rates. The experimental results showed that notch geometry significantly affects the discharge coefficient. For smaller flows, multiple narrower triangular notches were found to be more precise than a single wide rectangular notch.
Rheology pharmaceutics ppt by muhammaad ahmadAhmadAslam39
The document defines rheology as the science concerned with the deformation and flow of matter under stress. It discusses key rheological concepts such as elastic deformation, plastic deformation, viscosity, and Newtonian and non-Newtonian fluids. Common types of non-Newtonian fluids include plastic, pseudoplastic, and dilatant fluids. The document also outlines several methods for measuring viscosity and the importance of rheology in pharmaceutical applications such as ensuring stability, improving solubility and bioavailability, and optimizing manufacturing processes.
1. The document describes an experiment conducted to determine the rheological properties of viscosity and yield point of a drilling fluid sample using a Fann viscometer.
2. Key aspects of the experiment included preparing the mud sample, measuring its viscosity at 300 and 600 RPM, and determining its plastic viscosity and apparent viscosity. Calibration of the Marsh funnel and factors affecting rheological properties are also discussed.
3. Sources of potential error in measuring viscosity are described, such as improper mud weight, excess or insufficient fluid, and improper reading of the measuring scale.
This document discusses Newtonian and non-Newtonian fluid behavior. It defines Newtonian fluids as those whose shear stress is directly proportional to shear rate, while non-Newtonian fluids do not follow this relationship. The document categorizes non-Newtonian fluids as time-independent or time-dependent, with time-independent fluids further divided into shear thinning, dilatant, and visco-plastic and time-dependent fluids exhibiting thixotropic or rheopectic behavior. Examples are given of materials that demonstrate different non-Newtonian behaviors along with diagrams of characteristic flow curves. Rheology is defined as the study of flow and deformation of materials.
This document discusses rheology and viscosity. It defines rheology as the science of flow of fluids and deformation of solids under stress. Viscosity is a measure of a fluid's resistance to flow and is important in formulation of products like creams, ointments, and suspensions. The document describes different types of fluid flow based on viscosity, such as Newtonian, plastic, and pseudoplastic flow. It also discusses instruments used to measure viscosity like capillary, falling sphere, cup and bob, and cone and plate viscometers. Thixotropy, where the viscosity of a fluid decreases under shear stress over time, is also covered.
Rheology is important for pharmacists in understanding the flow properties of emulsions, suspensions, and other dosage forms. It also affects the selection of processing equipment and containers. For suspensions and emulsions, rheology determines properties like sedimentation, redispersibility, and flow characteristics. The viscosity and rheological class (e.g. Newtonian, pseudoplastic) of a dosage form depends on factors like particle size, concentration, and choice of suspending agent. Container materials must be compatible with the dosage form and maintain seal integrity over time. Rheology is a key consideration in designing stable, easily administered pharmaceutical preparations.
Fluid Flow in Bioprocesses
A fluid is a substance that undergoes continuous deformation when subjected to a shearing force.
Fluids play a central role in bioprocesses since most of the required physical, chemical, and biological transformations take place in a fluid phase.
In bioreactors, fluid properties play a key role in determining the effectiveness of mixing, gas dispersion, mass transfer, and heat transfer.
The science of flow of fluid and its deformation under applied forces is termed as rheology.
Polymer Rheology(Properties study of polymer)Haseeb Ahmad
This document discusses fundamentals of polymer rheology. It defines rheology as the study of flow of matter, primarily liquids but also soft solids. Rheology is important for characterizing polymers and understanding how polymer structure affects processing behavior. The document describes different types of fluids and their viscosity properties. It also discusses various rheological measurement techniques like rotational rheometers, capillary rheometers and melt flow indexers.
Rheology is the study of flow and deformation of matter. It describes the relationship between force, deformation, and time for all materials from gases to solids. There are two categories of flow - Newtonian and non-Newtonian. Newtonian fluids have a linear stress-strain relationship while non-Newtonian fluids have nonlinear or time-dependent relationships. Examples of non-Newtonian flows include plastic, pseudoplastic, and dilatant flows. Rheology is important in many fields including pharmaceuticals, food, concrete, and physiology.
This document discusses rheology and viscosity measurement techniques. It covers key topics like:
1) Newtonian and non-Newtonian flow, including plastic, pseudoplastic and dilatant systems.
2) Measurement of viscosity using viscometers like capillary, falling sphere and rotational viscometers.
3) Phenomena like thixotropy, antithixotropy and their significance in formulations.
The document provides an overview of important rheological concepts and methods to characterize the flow behavior and viscosity of formulations.
Physical Pharmacy M02 discusses rheology and the measurement of viscosity. It covers Newtonian and non-Newtonian flow, including plastic, pseudoplastic, and dilatant behaviors. Key concepts are thixotropy and antithixotropy. Methods to measure viscosity include capillary, falling sphere, and rotational viscometers. Understanding viscosity is important for formulating drug delivery systems and ensuring patient acceptability.
Metal chelating agents are used to treat toxicity from heavy metals like arsenic, lead, and mercury. Common chelating agents include dimercaprol, DMPS, EDTA, DMSA, penicillamine, and DTPA. They work by forming stable complexes with metals, allowing the metals to be removed from the body through excretion. While chelating agents are effective at removing metals, they must also have a low affinity for essential metals like calcium and zinc to avoid depleting these nutrients. Arsenic is one of the most toxic heavy metals and exposure can occur through contaminated water, pesticides, or occupational sources. After absorption, arsenic accumulates in tissues and symptoms of toxicity can appear with ingest
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1. The document outlines the key steps in the mechanism of toxicity: delivery of the toxicant to its target, reaction with the target molecule, cellular dysfunction and toxicity, and repair or further damage.
2. Delivery is influenced by absorption, distribution, and metabolism/activation processes that determine the concentration of the "ultimate toxicant" at its site of action.
3. Distribution within the body and to specific target sites depends on properties like lipid solubility as well as specialized transport mechanisms. Binding to proteins can hinder distribution.
This document discusses toxicokinetics and provides details on absorption, distribution, and some of the mechanisms involved. It defines toxicokinetics as the process of uptake, biotransformation, distribution, and elimination of potentially toxic substances by the body. Absorption is described as the crossing of membrane barriers, with the major routes being skin, lungs, and gastrointestinal tract. Distribution is defined as the dispersion of substances among body compartments, determined by blood flow and diffusion. Volume of distribution is introduced as a useful concept for understanding distribution.
This document discusses the basic principles of toxicology. It covers topics like toxicity parameters, routes of exposure, dose-response relationships, and different types of toxicity. The key points are:
- Toxicity depends on factors like dose, duration, route of exposure, and individual susceptibility. Different toxic agents can cause different types of toxicity through various mechanisms.
- Common routes of exposure include ingestion, inhalation, skin contact, and injection. The route influences the toxicity level.
- There is usually a dose-response relationship where effects increase with dose. Individual and population responses must be considered.
- Toxicity can be acute, subchronic, or chronic depending on exposure duration and
This document provides an introduction to toxicology for 4th year medical laboratory students. It defines key terms like toxicology, toxin, toxicant, toxicity and discusses the historical aspects and development of toxicology as a field. It outlines the chapter which covers the introduction, historical aspects, definitions, classification, scope, nature of toxic response, routes of poisoning and potential causes of toxicity. The document discusses in detail the definitions, classification based on research methodology and specific issues, scope, nature of toxic responses including terms like LD50, routes of exposure and reversibility.
This document discusses pharmaceutical emulsions. It begins with definitions of emulsions and their types, including oil-in-water and water-in-oil emulsions. Theories of emulsification like the surface tension theory and oriented-wedge theory are explained. Methods for determining the emulsion type, such as dilution, conductivity, and dye tests, are outlined. The key steps in emulsion preparation include selecting emulsifying agents, preservatives, and other additives. Common emulsifying agents include synthetic surfactants, semi-synthetic and natural hydrophilic colloids, and finely divided solid particles.
This document discusses pharmaceutical suspensions. It defines a suspension as a dispersion where an insoluble solid drug is uniformly distributed throughout an external liquid phase. Suspensions are used when drugs are insoluble, to mask taste, or control drug release. Key factors in formulation include particle size control, wetting, sedimentation, Brownian motion, and electrokinetics. Approaches to formulation include structured vehicles, controlled flocculation, or a combination. Common ingredients and preparation methods are also reviewed.
This document is a chapter about colloidal systems from a book by Aliyi Gerina. It begins with an outline and learning objectives for the chapter. The introduction defines dispersed systems and classifies them as molecular dispersions, colloidal dispersions, or coarse dispersions based on particle size. Colloids can be further classified by the physical state of the dispersed and continuous phases. The chapter also describes the properties of lyophilic colloids, lyophobic colloids, and association colloids. It compares the solvation, preparation, viscosity, electrolyte effects, and other properties of these different types of colloidal systems.
The document discusses pharmaceutical solutions and their preparation. It begins with an introduction to different liquid dosage forms including solutions, suspensions, colloids, and emulsions. It then covers various topics related to solutions such as common solvents used, formulation considerations regarding solubility and stability, and classification of solutions based on route of administration or vehicle. Specific types of solutions are explained including those taken orally, used topically, and injected. Manufacturing considerations are also briefly mentioned.
This document discusses packaging and storage of pharmaceuticals. It covers various packaging materials like glass, plastics, and metals. It describes primary and secondary packaging as well as different types of containers, closures, and labeling requirements. The document also discusses stability studies, storage conditions, and establishing beyond-use dates to ensure pharmaceuticals maintain quality until the expiration date.
This document discusses solubility and distribution phenomena and was written by Aliyi Gerina from Bule Hora University. It defines key terms like solute, solvent, solution and solubility. It explains that solubility depends on interactions between solute and solvent molecules. Polar solutes dissolve best in polar solvents due to interactions like hydrogen bonding and dipole-dipole attractions. The document outlines factors that influence solubility such as temperature, pressure, and the ratio of polar to nonpolar groups in a molecule. It also discusses solubility of different forms of matter like gases in liquids, liquids in liquids, and solids in liquids.
This document summarizes key concepts about interfacial phenomena from a chapter in a pharmacy textbook. It discusses the different types of interfaces that can exist depending on whether two adjacent phases are in solid, liquid, or gaseous states. Important concepts covered include surface tension, interfacial tension, measurement methods, factors that affect surface tension like temperature and additives, and the spreading coefficient. Real-world examples of interfacial phenomena in various processes are provided.
This document discusses phase equilibrium and the phase rule. It begins with an introduction to intermolecular forces, including different types of intramolecular and intermolecular forces. It then discusses the phase rule, explaining that it relates the number of degrees of freedom in a system to the number of components and phases present. Various examples of how to apply the phase rule to different systems are provided. Finally, it briefly introduces the concept of a phase diagram for representing phase equilibrium conditions.
This document provides an introduction to pharmaceutical dosage forms and routes of drug administration. It defines key terms like pharmaceutics, dosage forms, active pharmaceutical ingredients and excipients. It also describes various solid dosage forms like tablets, capsules, lozenges and suppositories. Liquid dosage forms such as oral solutions, syrups, elixirs, emulsions and suspensions are also outlined. The document concludes by discussing solid and liquid dosage forms in detail.
Does Over-Masturbation Contribute to Chronic Prostatitis.pptxwalterHu5
In some case, your chronic prostatitis may be related to over-masturbation. Generally, natural medicine Diuretic and Anti-inflammatory Pill can help mee get a cure.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of the physiological basis of a normal electrocardiogram.
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1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar lead (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
6. Describe the flow of current around the heart during the cardiac cycle
7. Discuss the placement and polarity of the leads of electrocardiograph
8. Describe the normal electrocardiograms recorded from the limb leads and explain the physiological basis of the different records that are obtained
9. Define mean electrical vector (axis) of the heart and give the normal range
10. Define the mean QRS vector
11. Describe the axes of leads (hexagonal reference system)
12. Comprehend the vectorial analysis of the normal ECG
13. Determine the mean electrical axis of the ventricular QRS and appreciate the mean axis deviation
14. Explain the concepts of current of injury, J point, and their significance
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. Chapter 3, Cardiology Explained, https://www.ncbi.nlm.nih.gov/books/NBK2214/
7. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
- Video recording of this lecture in English language: https://youtu.be/kqbnxVAZs-0
- Video recording of this lecture in Arabic language: https://youtu.be/SINlygW1Mpc
- Link to download the book free: https://nephrotube.blogspot.com/p/nephrotube-nephrology-books.html
- Link to NephroTube website: www.NephroTube.com
- Link to NephroTube social media accounts: https://nephrotube.blogspot.com/p/join-nephrotube-on-social-media.html
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Basavarajeeyam is an important text for ayurvedic physician belonging to andhra pradehs. It is a popular compendium in various parts of our country as well as in andhra pradesh. The content of the text was presented in sanskrit and telugu language (Bilingual). One of the most famous book in ayurvedic pharmaceutics and therapeutics. This book contains 25 chapters called as prakaranas. Many rasaoushadis were explained, pioneer of dhatu druti, nadi pareeksha, mutra pareeksha etc. Belongs to the period of 15-16 century. New diseases like upadamsha, phiranga rogas are explained.
Histololgy of Female Reproductive System.pptxAyeshaZaid1
Dive into an in-depth exploration of the histological structure of female reproductive system with this comprehensive lecture. Presented by Dr. Ayesha Irfan, Assistant Professor of Anatomy, this presentation covers the Gross anatomy and functional histology of the female reproductive organs. Ideal for students, educators, and anyone interested in medical science, this lecture provides clear explanations, detailed diagrams, and valuable insights into female reproductive system. Enhance your knowledge and understanding of this essential aspect of human biology.
Muktapishti is a traditional Ayurvedic preparation made from Shoditha Mukta (Purified Pearl), is believed to help regulate thyroid function and reduce symptoms of hyperthyroidism due to its cooling and balancing properties. Clinical evidence on its efficacy remains limited, necessitating further research to validate its therapeutic benefits.
Osteoporosis - Definition , Evaluation and Management .pdfJim Jacob Roy
Osteoporosis is an increasing cause of morbidity among the elderly.
In this document , a brief outline of osteoporosis is given , including the risk factors of osteoporosis fractures , the indications for testing bone mineral density and the management of osteoporosis
Osteoporosis - Definition , Evaluation and Management .pdf
Ch7. Rheology
1. Bule Hora University
College of Health and Medical Sciences
CHAPTER 7
Department Of Pharmacy
INTEGRATED PHYSICAL PHARMACY AND PHARMACEUTICS I
RHEOLOGY
By: Aliyi Gerina [B.pharm]
4/5/2022
1
Rheology by Aliyi G. Bule Hora University
2. Outline
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2
Introduction
Newtonian and Non-Newtonian systems
Thixotropy
Determination of viscosity
Different factors affecting rheological
properties
Pharmaceutical applications of rheology
Rheology by Aliyi G. Bule Hora University
3. Objectives
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3
At the end of this lesson the students should be able to:
Define rheology
Define and understand Newton's law of flow and its application
Differentiate flow properties and corresponding rheogram between
Newtonian and Non-Newtonian materials
Appreciate the fundamentals of determination of rheological properties
Recognize different factors affecting rheological properties of materials
Provide examples of fluid pharmaceutical products exhibiting various
rheological behaviors
Rheology by Aliyi G. Bule Hora University
4. Introduction
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4
o The term “rheology” from the Greek rheo (“to flow”) and
logos (“science”).
o It is defined as the science concerned with deformation of
matter under the influence of stress.
• Definition:
• the flow of fluids (liquids and gases) and
• the deformation of solids under the influence of shearing stress.
Rheology by Aliyi G. Bule Hora University
5. Introduction…
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5
The deformation of any pharmaceutical system can be
arbitrarily divided into two types:
• Elastic Deformation:
• it is a spontaneous and reversible deformation
• Plastic Deformation:
• it is a permanent and irreversible deformation
The plastic deformation: flow and exhibited by viscous bodies.
Great importance in any liquid dosage forms like
suspensions, solutions, emulsions etc
Rheology by Aliyi G. Bule Hora University
6. Introduction…
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6
Ideal solids deform elastically
The energy required for the deformation
is fully recovered when the stresses are removed
Ideal fluids such as liquids and gases deform irreversibly they flow
The energy required for the deformation
is dissipated within the fluid in the form of heat and
cannot be recovered simply by removing the stresses.
Rheology by Aliyi G. Bule Hora University
7. The deformation is recoverable if
the material returns to its initial
shape when the stress is removed.
Deformation is permanent if
the material remains deformed
when the stress is removed.
While elastic deformation is recoverable, plastic deformations are not
Recoverable versus permanent
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7
8. Importance of Rheology
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o In liquid, and semisolid DF: In preparation,
development and evaluation of suspensions, emulsions,
pastes, suppositories, tablets coating.
o The manufacturer of medicinal and cosmetic creams ,
pastes, and lotions must be able to pour the products
with an acceptable
o consistency and
o smoothness for each batch.
Rheology by Aliyi G. Bule Hora University
9. Importance of Rheology …
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9
o Rheology involved in
Mixing and flow of materials
Packaging into containers
Removal prior to use.
Whether this is achieved by
pouring from a bottle
extrusion from a tube or
passage through a syringe needle.
The product rheology must be optimized:
by controlling the viscosity of the product.
Rheology by Aliyi G. Bule Hora University
10. Importance of Rheology …
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o In acceptability to the patient, physical stability, and
even
biological availability (i.e., viscosity affect the
absorption rate of drugs from GIT).
o Rheology properties of pharmaceutical systems can influence
the selection of equipment used in its manufacture
Inappropriate equipment from rheological perspective may
result in an undesirable product, at least in terms its flow
characteristics.
Rheology by Aliyi G. Bule Hora University
11. Classification of rheological systems
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o Materials are classified according to type of flow in to two
categories
Newtonian systems
Simple fluids which obey Newtonian law of flow
Non-Nowtonian systems
do not obey Newtonian law of flow
Rheology by Aliyi G. Bule Hora University
12. Newtonian systems : Viscosity
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12
Measure of the resistance of liquid
to deformation under shear stress
A fluid’s internal resistance to flow
and may be thought of as a measure
of fluid friction
The resistance offered when one part
of the liquid flows past another.
Viscosity
The flow of liquids or semisolids is described by
viscosity.
13. 4/5/2022
13
Newtonian law of flow
o The phenomenon of viscosity is best understood by a consideration
of a hypothetical cube of fluid made up of infinitely thin layers
o which are able to slide over one another like a pack of playing cards.
o When a tangential force is applied to the uppermost layer
each subsequent layer will move at progressively decreasing
velocity and the bottom layer will be stationary.
Rheology by Aliyi G. Bule Hora University
Newtonian fluids: Viscosity…
15. 4/5/2022
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15
The bottom layer is considered to be fixed in place
The adhesive force between the wall and the flowing layers
Inter-molecular cohesive forces
Inter-molecular force (viscous forces) : viscosity
Viscosity is the opposing force to flow,
it is characteristic of the medium.
In other words, viscosity describes the internal friction of a
moving fluid.
Newtonian fluids: Viscosity…
16. 4/5/2022
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o A velocity gradient will therefore exist, and
o this will be equal to the velocity (ms-1) of the upper layer in
divided by the height (m) of the cube.
o Fig. Representation of the shearing force required to produce a definite velocity
gradient between the parallel planes of a block of material.
Rheology by Aliyi G. Bule Hora University
Newtonian fluids: Viscosity…
17. 4/5/2022
Rheology by Aliyi G. Bule Hora University
17
The difference in velocity (dv) b/n two planes
of a liquid separated by an infinitesimal
distance (dx) is the velocity gradient or a rate of shear
(dv/dx or G).
o The resultant velocity gradient is the rate of shear,
G, will have units s-1.
Shear rate (G) = dv/ dx
Newtonian fluids: Viscosity…
18. 4/5/2022
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18
The force required for one layer of a liquid to slip
past another layer with a given velocity depends
Directly
on the viscosity of the liquid and
on the areas of layers exposed to each other and
Inversely on the distance separating the two
surfaces.
A fluid with high viscosity resists motion
because its molecular make up gives it a lot of
internal friction.
18
Newtonian fluids: Viscosity…
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o The applied stress,the shear stress,
o S , is derived by dividing the applied force, F’, by the
area of the upper layer.
o It have units of N m-2.
Shear stress (S) = F’/ A
Rheology by Aliyi G. Bule Hora University
Newtonian fluids: Viscosity…
20. Newtonian fluids: Viscosity…
4/5/2022
Rheology by Aliyi G. Bule Hora University
20
Newton recognized that: the higher the viscosity of a liquid, the
greater the force per unit area required to produce a certain rate of
shear
Thus, the rate of shear is to the shearing stress
Newtonian law
dx
dv
A
F
'
dx
dv
A
F
'
Shear
of
Rate
Stress
Shearing
G
S
dx
dv
A
F
'
Where is a constant known as coefficient of viscosity,
usually referred to simply as viscosity or absolute
viscosity.
Where
S is the shearing stress (dyne.cm-2)
G is the rate of shear (sec-1)
Units: dynes-sec/cm 2
Absolute viscosity or dynamic viscosity
21. Newtonian fluids: Kinematic
Viscosity
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21
It is the absolute viscosity divided by the density of liquid
at a specified temperature.
KV = η/p
The preferred unit when the shear stress and shear rate of the
fluid
are influenced by the density.
Units: Stock (s) or centistokes .
22. Newtonian fluids
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22
Liquids that obey Newton’s law of flow:
Newtonian liquids
Newton’s equation for the flow of a liquid is
S = η * G
Plot of shear stress Vs shear rate:
the slope gives the viscosity.
The curve always passes through the origin.
The reciprocal of viscosity is called fluidity: 1/η =
Slope
23. Characteristics of Newtonian flow
o The passage through the origin indicates
that
o even a mild force can induce flow in
these systems.
o The linear nature of the curve
shows that the viscosity (η) of a
Newtonian liquid
o is a constant unaffected by
the value of the rate of shear.
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Rheology by Aliyi G. Bule Hora University
24. Newtonian fluids…
4/5/2022
24
o Examples of Newtonian fluids include:
Water
Air
Glycerin and most mineral oil
True solutions
Very dilute suspension and emulsions
Liquid paraffin
Rheology by Aliyi G. Bule Hora University
25. 4/5/2022
25
o Most pharmaceutical fluids do not follow Newtonia
law
o because the viscosity of the fluid varies with the rate of
shear.
o These materials are non-Newtonian fluids.
o The viscosities of non-Newtonian fluids vary with
shear rate stating a single viscosity is misleading :
apparent viscosity
Rheology by Aliyi G. Bule Hora University
Non-Newtonian systems
26. Non-Newtonian system…
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26
o It can be seen in liquid and solid heterogeneous dispersions
o such as colloids, emulsions, liquid suspensions and ointments.
o there are three classes of non-Newtonian flow
plastic,
pseudoplastic
dilatant
Rheology by Aliyi G. Bule Hora University
27. Plastic flow (Bingham bodies)
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27
A plastic material does not flow
until a certain minimum shearing stress, the yield
value, is applied.
The substance initially behaves like an elastic body
and fails to flow when less amount of stress is
applied.
Further increase in the stress leads to a nonlinear
and increase in the shear rate which then turns to
linearity
28. Plastic flow,…
The slope of the rheogram is termed
mobility, analogous to fluidity in
Newtonian systems and its reciprocal
is known as the Plastic viscosity, U
Where u is the plastic viscosity
and f is the Bingham yield
stress or value
4/5/2022
28
Rheology by Aliyi G. Bule Hora University
29. Plastic flow,…
Extrapolations of the linear
plot gives ‘x’ intersect: yield
value.
This curve does not pass
through the origin
Intersects the shear stress
axis at a particular point, yield
value.
As the curve above yield value
tends to be straight,
the plastic flow is similar to the
Newtonian flow above yield
value. 4/5/2022
29
Rheology by Aliyi G. Bule Hora University
30. Plastic flow,…
4/5/2022
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30
Flocculated particles in a concentrated
suspensions usually show plastic flow.
The yield value represents the stress required to break the
inter-particular contacts so that particles behave
individually.
Thus it is indicative of the forces of flocculation
increased by the increased concentration of the
dispersed phase.
32. Plastic flow,…
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32
o Other examples of plastic flow:
Solid powder materials
Topical ointments
Pastes
Rheology by Aliyi G. Bule Hora University
33. 4/5/2022
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33
Pseudo plastic flow is exhibited by polymer
dispersions like:
Tragacanth in water
Sodium alginate in water
Methyl cellulose in water
Sodium carboxy methyl cellulose in water
Pseudo-plastic Flow (shear thinning)
34. Pseudo-plastic Flow…
The relationship between shear
stress and the shear rate
is not linear and the curve
starts from origin.
The viscosity of a pseudo-
plastic substance decreases
with increasing G (shear-
thinning systems).
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Rheology by Aliyi G. Bule Hora University
35. Pseudo-plastic flow behavior; Structural reasons
4/5/2022
Rheology by Aliyi G. Bule Hora University
35
At rest, the linear polymers dispersed at random in
the dispersion medium.
As shearing stress is applied, the macromolecules
become aligned with the long axis parallel to the
direction of flow.
With this ordered alignment the molecules pass one
another with less frictional resistance, and the
viscosity is decrease.
38. 4/5/2022
Rheology by Aliyi G. Bule Hora University
38
If the S is decreased, the orientation of the
macromolecules becomes more random.
Greater frictional resistance to the flow is reflected
in an increased viscosity.
Since only a molecular alignment is involved
Emulsions and dispersions of many types: shear-
thinning
Pseudo-plastic Flow…
39. Dilatant Flow(Shear
thickening)
4/5/2022
Rheology by Aliyi G. Bule Hora University
39
Resistance to flow (viscosity) increases with
increase in shear stress.
When S is applied their volume increases and
hence they are called Dilatant.
This property is also known as shear thickening
Dilatant flow is observed in suspensions
containing
more than 50%W/V of solids,
deflocculated particles .
41. Dilatant Flow,…
4/5/2022
Rheology by Aliyi G. Bule Hora University
41
At rest, the particles are closely packed with a
minimum interparticle volume, or voids.
The vehicle is sufficient to fill this volume.
As the shear stress is increased, the bulk of the
system expands or dilates.
Increase in the inter-particle void volume
Vehicle become insufficient to fill the increased voids.
• The resistance to flow increases:
This process is reversible
42. Dilatant Flow,…
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42
o The effect is reversible and removal of the shear stress
results in the re-establishment of the fluid nature.
Rheology by Aliyi G. Bule Hora University
43. Dilatant Flow,…
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43
o Dilatancy can be a problem during the processing
of dispersions and the granulation of tablet masses
when high-speed blenders and mills are employed.
If the material being processed becomes dilatant in nature
then the resultant solidification could overload and
damage the motor.
Rheology by Aliyi G. Bule Hora University
45. 4/5/2022
45
o Non-Newtonian,
Time dependent behavior.
o Definition
o Thixotropy: It is the decrease in viscosity as a function
of time upon shearing, then recovery of original viscosity
as a function of time without shearing.
o Thixotropic material is
o any material that exhibits a reversible time-dependent decrease
in apparent viscosity.
Rheology by Aliyi G. Bule Hora University
Thixotropy
46. Thixotropy,...
4/5/2022
Rheology by Aliyi G. Bule Hora University
46
Thixotropic substances on applying shear stress
convert to sol (fluid) and on standing they
slowly turn to gel (semisolid).
47. Reason for thixotropic property
Thixotropic systems contain
asymmetric particles which
set up a loose three
dimensional structure which
is
rigid and resembles a gel
which is broken down on
applying shear: Solution
On removing the applied
stress, the material reform its
original structure of state: Gel
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Rheology by Aliyi G. Bule Hora University
48. Thixotropy,...
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48
o Rheogram : show a hysteresis where, as the S
is increased an up-curve is obtained, on
reducing the S gradually a down curve shifted to
the left side is obtained.
o In the case of
o plastic and
o pseudoplastic materials the downcurve will be
the right of the upcurve.
49. Thixotropy,...
Rheogram of thixotropic materials depends on
Applied shear rate or shearing force
The length of the time a sample is subjected to
shearing or kinematic history.
The previous history of the sample has
significant effect on
the rheologic properties of a thixotropic system.
50
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Rheology by Aliyi G. Bule Hora University
50. Thixotropy,...
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Thixotropic substances are now a day’s more used in
suspensions to give stable suspensions.
On storage turn to gel: viscosity increases infinitely, do
not allow the dispersed particles to settle down:
stable suspension
When shear stress is applied they turn to solution and
thus are easy to pour and measure for dosing.
Solve the problems,
stability and
pourability.
51. Thixotropy,...
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Examples
Gels that show thixotropic flow
include aluminum hydroxide gel and bentonite magma
Paints are also another example of thixotropic fluids
When modern paints are applied the shear created by the
brush or roller will allow them to thin and wet out the
surface evenly
Once applied the paints regain their higher viscosity
which avoids drips and runs.
52. Irreversible Thixotropy
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Application of shear stress causes breakdown of
structure within the system but
The structure does not reform on removal of the
shear stress, or
The time lag is so long that from a practical point of
view the effect is irreversible.
Example: gels produced from higher M.Wt
polysaccharides
On application of high shear,
The 3D structure of the polysaccharides is reduced
to a 2D one and
The original gel-like structure is never
53. Negative thixotropic or Antithixotropy
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Antithixotropy is believed to result from an increased collision
frequency of the dispersed particles in suspensions which
results in an increased inter-particle bonding with time.
This changes the original state of the system from a network of a
large number of individual particles and small floccules to an
equilibrium state consisting of a small number of relatively large
floccules.
Which helps the dispersed particles to acquire a random orientation
and the network is established: Gel
54. Negative thixotropic…
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At rest the large floccules break up and gradually return to
the original state of small floccules and individual particles.
viscosity decreases: Solution
Negative thixotropic or Antithixotropy…
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Rheopexy is the conversion of solids to gel up on
application of shearing stress.
Substances with low melting point
shows rheopectic property.
Example: polymers with low melting point
Rheopectic fluids are rarely encountered
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o Different equipments called viscometers are used to
measure rheological properties
o such as viscosity of different fluids and semisolids.
o Successful determination and evaluation of rheologic
properties of any particular system depend on choosing the
correct instruments
For Newtonian system
Single point instruments can be used
Instruments that operate at a single rate of shear.
For no-Newtonian system,
multipoint instruments should be used
instruments that can operate at different rates of shear
Rheology by Aliyi G. Bule Hora University
Determination of the rheological
properties
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Ostwald Viscometer
It is a type of capillary viscometer
This is ‘U’ shape tube with two bulbs and two
marks .
It is used to determine the viscosity of
Newtonian liquids.
Rheology by Aliyi G. Bule Hora University
58. Determination of the rheological properties…
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Principle:
When a liquid flows by gravity, the time required for
the liquid to pass between two marks, upper mark
and lower mark,through a vertical capillary tube is
determined.
The time of flow of the liquid under test is compared
with the time required for a liquid of known viscosity
(usually water).
59. Determination of the rheological properties…
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The viscosity of unknown liquid η1 can be
determined using the equation
η1 = (ρ 1t1 ) η2
ρ 2t2
ρ1= Density of unknown liquid
ρ2= Density of known liquid
t1= Time of the unknown liquid
t2= Time of the known liquid
η 2= Viscosity of known liquid
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Falling-sphere viscometer
Consists of cylindrical transparent tube having
graduated section near the middle of its length and
generally a steel ball that is allowed to fall through
the tube.
Rheology by Aliyi G. Bule Hora University
61. Determination of the rheological properties…
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The tube is filled with the liquid whose viscosity is to be
determined and the ball is allowed to fall.
The velocity of the falling ball is measured and viscosity is
calculated using stoke’s law
V= d2 (ρ s- ρ o ) g
18
where d= Diameter of the falling ball; ρ s =Density of the
ρ l=Density of liquid; g= Gravitational acceleration; v =
settling velocity
As d2g/18 is constant, can be replaced by another
constant ‘K' Therefore, the equation will be
= K(ρ s- ρ 1 )
V
62. Factors affecting rheological properties
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Chemical factors
Extent of Polymer Hydration
In hydrophilic polymer solution the molecules are
regarded as completely surrounded by
immobilized water molecules forming a solvent
layer.
Such hydration of hydrophilic polymers gives rise
to an increased viscosity.
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Impurities, Trace Ions and Electrolytes
Chemical impurities are the major factors in
changing the viscosity of natural polymers.
At high conc. =>compete for adsorbed water
molecules surrounding the hydrated polymer =>
the polymer become dehydrated => the
viscosity of the dispersion decreased =>
precipitation occurs.
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Physical factors
Temperature
A temperature increase usually produces a rapid
viscosity decrease.
Prolonged heating may produce drastic decrease in
viscosity
due to decomposition of the polymer,
e.g., gelatin.
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Concentration
In concentrated suspensions:
a decrease in particle size or an increase in the
surface area of the solid phase produce an
increase in the viscosity of the system.
This due to immobilization of the vehicle with an
increase in
the fraction of the suspension volume occupied by the
solid.
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Rheology of emulsion
o All except dilute medicinal emulsions exhibit
o non-Newtonian behavior.
o The fluid emulsions
o are usually pseudoplastic.
o Those approaching a semisolid nature behave
o plastically.
o The semisolid creams
o are usually viscoelastic.
Rheology by Aliyi G. Bule Hora University
Significance of rheology
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Rheology of suspension
o Most exhibit plasticity and pseudoplasticity along
with thixotropy.
o The rheological properties of suspensions are
markedly affected by
the degree of flocculation
The types and quantities of suspending and
thickening agent.
o Preferred rheological properties
Pseudoplasticity along with thixotropy
Rheology by Aliyi G. Bule Hora University
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o Flocculated suspensions will exhibit
o plastic or
o pseudoplastic (more usually) behaviour.
o If the breakdown and reformation of the bonds between
floccules is time dependent then thixotropic behaviour
will also be observed.
o Concentrated deflocculated suspensions exhibit
o dilatancy.
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69. Significance of rheology …
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Rheology of semisolids
o Rheological characteristics of semisolids
affect
The stability and their extrudability from tubes
The capacity to take up solids or liquids
The spreadabilty on the skin and
Release of active from the base.
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o Most of the topical semi-solids
o show plastic flow behaviour.
o Hydrocarbon bases (e.g petrolatum) exhibit
o plastic flow with varying degree of thixotropy..
o Some paste exhibit
o dilatancy when subject to shear where as others demonstrate
typical
o pseudoplastic flow with thixotropy
Rheology by Aliyi G. Bule Hora University
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Rheology of powders
o Good flow property of powder are required to ensure
uninterrupted flow from hopper and into the die
cavities
in high speed tabletting machines
during encapsulation and
during the packaging
o Factors affecting the flow properties of particulate
solid are
the surface characteristics and
Stickiness.
Rheology by Aliyi G. Bule Hora University
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o Improvement in the flow characteristics can be
achieved by
reducing the surface roughness of particle
reduced by the presence of fines in powder
which fill the irregularities.
reducing the stickiness b/n particles
reduced by the addition of lubricant
such as talc, starch and magnesium strearate
Rheology by Aliyi G. Bule Hora University
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Rheology and processing
o The rheological considerations of the material are
important
o to ensure proper mixing.
o Large impellar operating at a low shear rate is required
o for shear thinning systems.
o Semisolid material exhibiting dilatant properties
o should be processed with low shear mixer.
Rheology by Aliyi G. Bule Hora University
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o Low shear mixing is sometimes required in certain
polmeric dispersion
o in order to prevent the breakdown of struture due to
depolymerisation at high shear rates.
o Rheological considerations are also important
o during fluid transfer including pumping from one vessel
to another and flow though pipes.
Rheology by Aliyi G. Bule Hora University
The viscosity of Newtonian system can be expressed as absolute viscosity.
gels produced from higher molecular weight polysaccharides which are stabilized by large number of secondary bonds. Yoghurt serves as a counter example, it becomes thinner when stirred, but does not returns to its original thickness. So it does not exhibit thixotropic flow behavior.
Antithixotropic systems have low solid content(1-10%) and are flocculated…the equilibrium state is solution. Deflocculated suspensions of a solid content of less than 10% shows increase in viscosity are termed as antithixotropy this are called magmas, magnesium magma and milk of magnesium.
Antithixotropy is essentially the opposite of thixotropy, in that the fluid’s viscosity ↑ with time as it is sheared at a constant rate . The gentle rolling or rocking motion provides a mild turbulence Which helps the dispersed particles to acquire a random orientation and the network is re-established