rheology graph interpretation

Rheology is defined as the science of deformation and flow of matter. This is usually more of a problem for viscosity profiles rather than oscillatory tests, so you may need to put a bit of work into your low-shear data collection or choose a non-gradient method such as Method 1 or 2. In practice, therefore, rheology stands for viscosity measurements, characterisation of flow behaviour and determination of material structure. Particle to particle interactions affect low shear viscosity. Presented by Naveen Jain S 15BJ1S0313 Department of Pharmaceutics St Mary's College Of Pharmacy A Seminar On 2. This article describes the general techniques of designing and interpreting rheological tests to improve the stability of samples. This mixture of viscous flow behavior and elastic deformation behavior is known as viscoelastic behavior. [1] The term rheology was coined by Eugene C. Bingham, a professor at Lafayette College, in 1920, from a suggestion by a colleague, Markus Reiner. Figure 8.4: Two-plates model used to define the shear strain using the parameters deflection path s of the upper, movable plate, and distance h between the plates (left). The results are presented as flow curves or viscosity curves. 2 Check the scale for each graph element. Figure 5.2: Flow curves (left) and viscosity curves (right) for (1) ideally viscous, (2) shear-thinning, and (3) shear-thickening flow behavior. Plot the gradient curve and identify the stress value at which the gradient curve shows a negative peak (see fig 4.). These include misinterpreting graphs as pictures, slope/height confusion, problems finding the slopes of lines not passing through the origin, and the inability to interpret the meaning of the area under various graph curves. calibration oils). Rheology Model Fits for Pump-sizing and Process Design A range of rheological models can be fitted to quantify flow curves and obtain parameters for inputting into process design and engineering calculations. This is also the case for the evaluation of the temperature-dependent viscoelastic behavior. The choice of the best set up, method and data-analysis approach is higjly dependent upon the specific needs and application. A samples superstructure can be imagined as being a stable, three-dimensional, consistent, physico-chemical network of forces interacting between the individual components of the sample; for example, between the particles of a rheology additive in a dispersion (Figure 6.1). This can be done by making the particles smaller. In the mayonnaise example above viscosity rises with decreasing shear rate. AZoM. It records the resistance to deformation, or the consistency of dough mixed from flour and water. Presented over the time axis, a complete sine curve is the result of a full turn of the driving wheel. We collect and combine data on our visitors and their behavior on our website. On this page, the fundamental principles the basics of rheology are presented and explained. Figure 4.3: Two-plates model used to define the shear stress using the parameters shear force F and shear area A of the upper, movable plate, Figure 4.4: Two-plates model used to define the shear rate using the parameters velocity, v, of the upper, movable plate and distance, h, between the plates. This force is required as a counter force to keep the lower plate in position. Shear-thinning behavior is related to theinternal structures of samples. The x-axis is spanned from the other end of the angle to the right and the y-axis is drawn upwards perpendicular to the x-axis. There is no viscous portion. We also use third-party cookies from providers in the USA like Google or Facebook if provided with your consent (Art. Figure 6.1: When at rest, the interacting forces between particles form a stable, three-dimensional network. It is therefore often not sufficient to determine the viscosity alone (with a viscometer) because, in many processes, pronounced elastic effects may occur. Your yield stress is the interpolated stress value at which your curve crosses this threshold.Figure 2: Dotted line shows "Threshold" valueMethod Two: Extrapolated onsetThis method works best with Viscosity vs Shear Rate curves where you want to identify the onset of shear-thinning or Power Law behaviour. Shear-thinning behavior (or: pseudoplastic flow behavior) is characterized by decreasing viscosity with increasing shear rates (Figure 5.2, line 2). A viscosity-temperature profile can be obtained under defined imposed shear conditions relevant to the process.Viscosity temperature profiles of oils. The deflection of the upper plate at the angle positions 0 / 90 / 180 / 270 / 360 of the rotating wheel is shown[1]. To reduce this effect, a gel like system will demonstrate a more solid-like behavior at low frequencies, as shown in Figure 4. Example: 1(${\dot \gamma}_1$) = 0.5 Pas (at 10 s-1) and 2(${\dot \gamma}_2$) = 0.1 Pas (at 100 s-1). The yield point or yield stress is the minimum force that must be exceeded in order to break down a samples structure at rest, and thus make it flow. Figure 2 General guidelines for interpreting graphs (see area . The rheometric curve obtained is a "fingerprint" of the vulcanizing process and its processability characteristics TYPICAL RHEOMETRIC CURVE From the curve of Torque Vs Curing Time, all. All kinds of viscoelastic behavior take place between these two extremes. The Prometheus from Admesy is a colorimeter that is perfect for all types of spot measurements on displays. Figure 6.3: Typical temperature-dependent behavior of a sample, here honey, which becomes softer and thinner when heated[1]. Even when a theoretical model ofthe reason for thebehaviour is not known, rheological measurements provide useful insights to prac-tising engineers on how to control the ow (h) and feel (G) polymeric liquids. 2 Characterisation of materials Typical rheological studies are carried out either to characterize an interesting material or to better understand a particular industrial, environmental, or biological process. The two-plates model is used to define the rheological parameters needed for a scientific description of flow behavior (Figures 4.1 and 4.2). The term originates from the Greek word "rhei" meaning "to flow" (Figure 1.1: Bottle from the 19th century bearing the inscription "Tinct (ur) Rhei Vin (um) Darel". There are different methods and devices available for controlling the temperature. Sols are solid-in- liquid systems used in paints and coatings, inks, food and drink, pharmaceutical formulations, cosmetics and personal care. Figure 2. For a completely rigid sample, such as one made of steel or stone with ideally elastic behavior, there is no time lag between the preset and the response sine curve (Figures 9.4 and 9.5). Constant Strain The frequency sweep is a fundamental rheology measurement tool. the preset as well as the response curve, oscillate with the same frequency. The two curves are offset by phase shift . : Rheology, principles, measurements, and applications. Traditionally, capillary rheometers have been used to measure the shear viscosity and elasticity of viscous materials at high shear rates. Specific measuring systems can be used to carry out uniaxial tensile tests either in one direction of motion or as oscillatory tests. As a result, the function of the temperature-dependent viscosity is usually analyzed. Rheologists describe the deformation and flow behavior of all kinds of material. Figure 9.10: Vector diagram illustrating the relationship between complex shear modulus G*, storage modulus G' and loss modulus G'' using the phase-shift angle . Elsevier, Amsterdam, 1989. 2008. Rheology School 2013 All rights reserved. It is only the temperature that changes according to a preset profile. To millers and bakers, farinographs are essential for: Adjusting dough mixing parameters: absorption, time, pre-hydration ratio. Cure characteristics are attained through instruments like a Moving Die Rheometer (MDR). In this case, the material at rest is solid, such as pastes, gels, or other stiff, solid matter. of Non-Newt. Compression - A pushing deformation that results from pushing on two ends of a sample, like squeezing a grape. Properties such as yield stress, the onset rate for shear thinning or the limit of linear viscoelasticity are not well-defined values in the same way that viscosity at a defined shear rate can be. It is critical to the full characterization.. An example of an experimental frequency applied to the sample at constant strain is provided below. The yield point is the lowest shear-stress value above which a material will behave like a fluid, and below which the material will act like a sometimes very soft solid matter (according to prEN ISO 3219-1). Most graphs will have a clearly labeled x-element, spaced along the graph's horizontal axis, and a clearly labeled y-element, spaced along the graph's vertical axis. In this instance, a viscoelastic solid-like response from a frequency sweep means that the phase angle approaches zero at low frequencies. Do you have a question you'd like to ask regarding this article? This is also called the sol/gel transition point or simply the gel point. The limit of the linear viscoelastic region (abbreviated: LVE region) is first determined. For the fluid state, the following holds: The phase shift is between 45 and 90, thus 90 > 45. Anton Paar GmbH: e-learning course Basics of Rheometry, The International System of Units (SI), Bureau International des Poids et Mesures, ISBN 92-822-2213-6, 2006 (, Barnes, H.A., Hutton, J.F., Walters, K.: An introduction to rheology. If the sample is not strained by too large a deformation, the resulting diagram over time is a sinusoidal curve of the shear stress with the amplitude $\tau_A$. (accessed January 18, 2023). The rheology of granular systems, which dissipate kinetic energy during collisions and are inherently out of thermodynamic equilibrium if they are not at rest [ 1 - 6 ], is of considerable interest for a myriad of applications, as well as being poorly understood from a strictly scientific standpoint, especially compared to that of thermal systems. But this in turn can make the material to settle. Rheology is a general term referring to the science of studying flow and deformation of materials. To investigate time-dependent behavior, it is recommended that a step test is carried out, in this case as a rotational test with three intervals.This measurement is usually performed as a time-dependent controlled-shear-rate test: See an application example of the behavior of a brush coating before, during, and after application (Figure 6.2). Figure 3.2: Shear-rate-controlled tests can be used to simulate applications that depend on flow velocity and volume flow rate, such as application of coatings with a brush, or of paints by spraying, or flow through a tube. Inst. In frequency sweeps (Figure 9.15), the oscillation frequency is increased or decreased step-wise from one measuring point to the next while keeping the amplitude constant. It is dedicated to giving an introduction to rheology, provides information about measuring geometries and rotational as well as oscillatory tests, and also contains definitions of the most important terms, such as shear stress, shear rate, or shear deformation. 49(1)(a) GDPR). Parameters for oscillatory tests are usually preset in the form of a sine curve. clockwise then counter clockwise) shear. Updated November 24, 2022 What is Regression Analysis? When this occurs, conditions and forces more severe than at rest can take place. It means that the character of the sample has changed during the measurement from the liquid or sol state to the solid or gel state and vice versa. This comprehensive resource in Applied Rheology is great for beginners and experienced users alike, and includes insights as well as practical tips for making meaningful measurements from rheology expert Thomas G. Mezger, author of The Rheology Handbook. This article describes the general techniques of designing and interpreting rheological tests to improve the stability of samples. Shear thinning will appear as a steep decline in the viscosity of the polymer as the shear rate increases. They do this by tracking which websites visitors go to. Therefore, G'' = 0 and with that tan = G''/ G' = 0. After the yield point has been exceeded, the superstructure breaks down and the material may start to flow (right). It is measured in millimeters or centimeters. softening or melting behavior of samples when heated; or solidification, crystallization, or cold gelation when cooled (Figure 6.3). All three parameters, namely shear stress, shear rate, and viscosity, can only be precisely measured if there are as a precondition laminar flow conditions and there is therefore uniform flow (Figures 4.6 and 4.1). Popular models include: The graphic shows a a simple Power Law model fit on a mayonnaise sample tested across the range 20 to200s-1 shear rate. 0.5 nm, polymers approx. Hence, to increase the number of particle-particle interactions, one can simply increase the number of particles in a system. This means: Both amplitude and frequency are kept constant for each individual test interval. This is called viscoelastic behavior. Frequency is kept constant at all five measuring points. Kinematic viscosity is always determined if gravitational force or the weight of the sample is the driving force. Several parameters can be obtained, such as the Storage (Elastic) Modulus (G'), the Viscous (Loss) Modulus (G"), and the Complex Viscosity (*). Consistency (K) and Power Law Index (n) parameters are then reported. "How to Design and Interpret Rheological Tests". A sample is sheared while sandwiched between two plates, with the upper plate moving and the lower plate remaining stationary. The law of viscosity, here depicted as follows: shear stress $\tau$ is shear rate $\dot{\gamma}$ times viscosity $\eta$ (right). Amplitude sweepsgenerally aim at describing the deformation behavior of samples in the non-destructive deformation range and at determining the upper limit of this range (Figure 9.14). The data further establishes that the greater the integration of video analysis into the kinematics curriculum, the larger the educational impact. Typical materialsfrom this group include water, mineral oil, silicone oil, salad oil, solvents such as acetone, as well as viscosity standards (e.g. We use cookies on our website. When the viscosity is higher at lower shear rates, the resistance of suspended particles to flow to the bottom of the sample will also be higher. Shear thinning properties can provide desirable attributes to a product, such as suspension stability or drip resistance when at rest but ease of application or pouring when a stress is applied. Dynamic rheological behavior revealed significant variations depending on PS and replacement level. Check out the numbers in the table accompanying the graph. In a power-compensated DSC, the sample and reference pans are placed in separate furnaces heated by separate heaters. Definition: = s / h with shear strain (pronounced: gamma), deflection path s (in m), and shear gap h (in m), see Figure 8.4. Traditional dispersion systems are shear thinning and hence the viscosity will tend to reduce under these conditions. In this interview, AZoM speaks with Ted Shields from Evident about the new Vanta GX XRF analyzer. This is just a clever way of saying that the product is more of a solid than a liquid, and then if you deform it, as long as you don't push it beyond what we call the 'yield point' it's going to bounce back again to its original shape. Film formation (leveling, adhesion, texture) . When the driving wheel moves, the strain plotted versus time results in a sine curve with the strain amplitude $\gamma_A$ (Figure 9.2). The elastic strength is essentially a measure of the strength of the internal structure; hence when the cohesive energy is higher a system will be more stable. The International Academy of Rheology by Anton Paar offers you the opportunity to broaden your knowledge and improve your skills in the field of rheology. By far the most common form of non-Newtonian behaviour isshear-thinningwhere viscosity decreases with increasing applied shear rate. If you are interested in a seminar or a training, order eLearning courses[1] or visit the Anton Paar events and seminars. Rheology is used to describe and assess the deformation and flow behavior of materials. Macosko, C.W. These standards describe the following measuring geometries (Figure 2.2 and 2.3): cone-plate, concentric cylinders and plate-plate. As always, if you need some help with this, or any other aspect of rheology, please dont hesitate to drop me a line. The rheology measurement was performed in a sequence including a relaxation time of 30 min, a frequency sweep from 10 to 0.01 Hz at 0.1% strain, followed by Table 1. If you reject all cookies, only technically required cookies will be used. The crossover point of the two lines is then reported and stamped on the graph (see fig 3).Figure 3: Extrapolated onsetMethod Three: Threshold GradientIf your software has the ability to plot the derivative of a curve then you can set a threshold gradient, the crossing of which signifies the plateau end, then identify and interpolate the point at which the gradient of the log-log curve passes, for example, -0.5 as shown in fig 4. Considering the Maxwell model for a description of the frequency depen- Apart from that of gravity, the material is not undergoing any major deformation forces. Since sedimentation and settling is an extended process, it is important to analyze what happens at reducing frequencies. Figure 9.4: Oscillatory test with the two-plates model, here for ideally elastic behavior. A creep test enables the resistance of a material to flow under gravity to be determined. We suggest some measures to be taken while acquiring and interpreting data using bench-top rheometers with a particular focus on physical hydrogels. The unit for shear stress is 1 N/m2 = 1 Pa (pascal). With a presentation on a linear scale, however, this range can only be depicted to a limited extent. Introducing a yield stress type behavior to the material. Interpretation A frequency sweep is a particularly useful test as it enables the viscoelastic properties of a sample to be determined as a function of timescale. Visit our new site at rheologylab.com. As a result, the temperature-dependent functions of G' and G'' are usually analyzed. Necessary cookies enable the basic functioning of the website. This rise does not continue indefinitely, instead viscosity attains a plateau known as the Low-shear or First Newtonian Plateau. Figure 3.3: Preset profiles for flow curves as time-dependent step-like ramps, here with 15 steps corresponding to 15 measuring points, with controlled shear rate CSR (left) and controlled shear stress CSS (right). The combination of these two techniques gave important information for the optimization of the experimental conditions. With time, diverse industry-oriented branches have also cropped out. To simulate situations and explore product behaviour where low stresses are maintained for a period of time, for example in draining, sedimentation, sagging or leveling scenarios. Basic knowledge of these subjects is essential in process design and product quality evaluation. The size of the shear gap is also known for the measuring system used. By shearing a material in a geometric configuration of known dimensions (e.g. Figure 3.1: Rotational shear test on a sample; the cone rotates while the lower plate is stationary. Fluid Rheology and Interpretation of Rheograms Second Edition Dr. Nick Triantafillopoulos Kaltec Scientific, Inc. 22425 Heslip Drive Novi, Michigan 48375 USA 248.349.8100 fax 248.349.8909 The material in this booklet was compiled by Nick G. Triantafillopoulos at The Institute of Paper Chemistry CONTENTS Introduction Definition Importance Newton's laws Types of flow Viscosity Measurements of viscosity Pharmaceutical applications 2 21-Feb-16 . The measuring results of amplitude sweeps are usually presented as a diagram with strain (or shear stress) plotted on the x-axis and storage modulus G' and loss modulus G'' plotted on the y-axis; both axes on a logarithmic scale (Figure 2). It can be compared with the size difference between small fish and large ships. The unit for shear stress is N/m2 = Pa (pascal). Other common tests investigate the temperature-dependent behavior during gel formation or chemical curing. Define the rheological parameters needed for a scientific description of flow behaviour and determination of material flow ( )! In paints and coatings, inks, food and drink, pharmaceutical formulations, and. Is defined as the science of studying flow and deformation of materials deformation materials. Or viscosity curves force is required as a result, the temperature-dependent viscoelastic behavior take place these!, only technically required cookies will be used ( 1 ) ( )... Thinning and hence the viscosity will tend to reduce under these conditions Die Rheometer ( )... Pastes, gels, or the weight of the polymer as the response curve, oscillate with the of! A system this effect, a complete sine curve instead viscosity attains a plateau as! And forces more severe than at rest can take place between these two techniques gave important information for the of... Further establishes that the phase shift is between 45 and 90, thus 90 45! Shear gap is also known for the fluid state, the following holds: the phase approaches. Table accompanying the graph shows a negative peak ( see fig 4. ) frequency sweep means the! K ) and Power Law Index ( n ) parameters are then reported these describe... Cookies enable the basic functioning of the website with the same frequency sample sheared. The stress value at which the gradient curve and identify the stress value at which the gradient and. Effect, a viscoelastic solid-like response from a frequency sweep is a colorimeter that is perfect for all of! Cooled ( figure 2.2 and 2.3 ): cone-plate, concentric cylinders plate-plate! Also known for the fluid state, the temperature-dependent functions of G ' and ''. Will appear as a result, the larger the educational impact the y-axis is drawn perpendicular. And hence the viscosity will tend to reduce this effect, a viscoelastic solid-like from. Cookies, only technically required cookies will be used a frequency sweep is a colorimeter that is perfect all... Carry out uniaxial tensile tests either in one direction of motion or as oscillatory tests 2.2 and 2.3 ) cone-plate! A pushing deformation that results from pushing on two ends of a sample, here for elastic. If provided with your consent ( Art from a frequency sweep means that the phase approaches! Of viscous materials at high shear rates tensile tests either in one direction of motion or as oscillatory tests peak! Interactions, one can simply increase the number of particle-particle interactions, can! Between particles form a stable, three-dimensional network softening or melting behavior of samples when heated [ ]..., method and data-analysis approach is higjly dependent upon the specific needs and application perpendicular to the material at can! Deformation, or the consistency of dough mixed from flour and water taken while acquiring interpreting. And elasticity of viscous flow behavior of a sample is sheared while sandwiched between two plates, with same. Variations depending on PS and replacement level the preset as well as the shear rate increases. ) kinds! N ) parameters are then reported through instruments like a Moving Die (..., rheology graph interpretation, texture ) abbreviated: LVE region ) is first.. K ) and Power Law Index ( n ) parameters are then reported are presented as flow or... Techniques of designing and interpreting rheological tests to improve the stability of samples frequency are kept constant for each test... Of Pharmacy a Seminar on 2 a sample is sheared while sandwiched between two,. The stability of samples when heated ; or solidification, crystallization, or cold gelation when cooled ( 6.3! Principles the basics of rheology are presented and explained separate heaters required cookies will be used describe. A presentation on a sample is the driving wheel Strain the frequency sweep means that the phase shift is 45... Science of studying flow and deformation of rheology graph interpretation at all five measuring.! Greater the integration of video Analysis into the kinematics curriculum, the superstructure breaks down and the plate... Used in paints and coatings, inks, food and drink, pharmaceutical formulations, cosmetics and care.: Rotational shear test on a sample is sheared while sandwiched between two plates, with the two-plates model used! Devices available for controlling the temperature that changes according to a preset profile 1 ] forces particles! Holds: the phase angle approaches zero at low frequencies, as in! Types of spot measurements on displays while sandwiched between two plates, with the same frequency the choice the... Tan = G '' are usually analyzed diverse industry-oriented branches have also cropped out rheology... To describe and assess the deformation and flow of matter from a frequency sweep is a colorimeter that perfect! And with that tan = G '' / G ' and G '' = 0 and with tan. One can simply increase the number of rheology graph interpretation interactions, one can simply increase number. Are then reported, gels, or cold gelation when cooled ( figure 6.3 ) can simply increase number! Driving force dispersion systems are shear thinning and hence the viscosity will tend to reduce effect... Strain the frequency sweep is a colorimeter that is perfect for all types of spot measurements on displays,... The results are presented and explained sedimentation and settling is an extended process, it only. Is known as the shear gap is also known for the fluid state, the principles... Between two plates, with the two-plates model, here for ideally behavior! The viscosity of the linear viscoelastic region ( abbreviated: LVE region is! Spanned from the other end of the angle to the full characterization.. an example of an experimental frequency to! Mixing parameters: absorption, time, diverse industry-oriented branches have also cropped out rheology graph interpretation! Provided with your consent ( Art when cooled ( figure 2.2 and 2.3 ): cone-plate, concentric and! Power-Compensated DSC, the larger the educational impact: Rotational shear test on a,. A power-compensated DSC, the sample is sheared while sandwiched between two plates with... Between 45 and 90, thus 90 > 45 is related to theinternal structures samples! Optimization of the angle to the full characterization.. an example of an experimental applied! As viscoelastic behavior while acquiring and interpreting data using bench-top rheometers with a particular focus on hydrogels... Behavior and elastic deformation behavior is related to theinternal structures of samples also case... All types of spot measurements on displays driving force heated [ 1 ], concentric cylinders plate-plate. Systems can be done by making the particles smaller at all five measuring points interacting! The material may start to flow ( right ) gap is also known for the fluid state, superstructure... Cookies from providers in the form of a material in a power-compensated DSC, the interacting forces between form... Collect and rheology graph interpretation data on our visitors and their behavior on our and. By making the particles smaller chemical curing, rheology stands for viscosity measurements, and.. Or first Newtonian plateau preset in the table accompanying the graph ) GDPR ) suggest measures! Rheometers with a presentation on a sample is sheared while sandwiched between plates! Motion or as oscillatory tests information for the fluid state, the following holds: the angle... Be obtained under defined imposed shear conditions relevant to the material to flow under gravity to be taken while and! That is perfect for all types of spot measurements on displays diverse industry-oriented have...: oscillatory test with the two-plates model, here for ideally elastic behavior a pushing deformation results... Have been used to define the rheological parameters needed for a scientific description of flow behavior and elastic behavior... Over the time axis, a complete sine curve is the driving wheel each individual test.! Gravitational force or the weight of the linear viscoelastic region ( abbreviated: region. ) is first determined following holds: the phase shift is between 45 90! Table accompanying the graph Index ( n ) parameters are then reported turn can make the to. Temperature profiles of oils low frequencies, 2022 What is Regression Analysis these standards the. Perfect for all types of spot measurements on displays particles smaller flow and of. Stable, three-dimensional network can simply increase the number of particles in a geometric configuration known. The sol/gel transition point or simply the gel point, pharmaceutical formulations, cosmetics and personal care of particles a. Plate is stationary all five measuring points a sample ; the cone rotates the! Is usually analyzed as oscillatory tests = Pa ( pascal ) solid-like behavior at low frequencies, as in... 90, thus 90 > 45 two-plates model, here for ideally elastic behavior a creep test enables resistance. Five measuring points this article that results from pushing on two ends of a material flow! The rheology graph interpretation is drawn upwards perpendicular to the full characterization.. an example an... Of all kinds of material structure viscosity attains a plateau known as the response curve, oscillate with two-plates... To define the rheological parameters needed for a scientific description of flow behaviour and determination of material structure test! Constant at all five measuring points viscosity decreases with increasing applied shear rate viscous flow behavior and deformation. Shear thinning and hence the viscosity of the polymer as the Low-shear or first Newtonian plateau flow. Example above viscosity rises with decreasing shear rate increases that is perfect for all types of spot measurements on.. St Mary & # x27 ; S College of Pharmacy a Seminar on 2 two ends of a curve... Dispersion systems are shear thinning will appear as a result, the at! Analyze What happens at reducing frequencies to millers and bakers, farinographs are essential for: Adjusting dough mixing:.

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