This document provides an outline for a course on rheology theory and applications. The course covers basics of rheology including definitions, types of rheometers, instrumentation, geometries, calibration, flow and oscillation tests, and applications. Specific topics include viscosity, linear viscoelasticity, transient testing, polymers, structured fluids, and advanced accessories. Rheology is introduced as the study of stress-deformation relationships in materials. Common geometries like parallel plates, cone and plate, and concentric cylinders are described along with considerations for choosing geometry size.
Vesicles are colloidal particles in which a concentric bilayer made-up of amphiphilic molecules surrounds an aqueous compartment Useful vehicle for drug delivery of both hydrophobic drugs and hydrophilic drugs, which are encapsulated in the interior aqueous compartment.
Biowaiver Based on BCS Classification System: Criteria and Requirements Accor...Tareq ✅
Bioavailability (BA)/bioequivalence (BE) parameters are generally required for approval of new and generic drugs. Bioequivalence based on plasma drug concentration has become the most frequently used and successful biomarker of safety and efficacy of a drug. According to the FDA’s regulations BA is defined as the rate and extent to which the active ingredient is absorbed from a drug product and becomes available at the site of action and BE can be defined as the absence of a significant difference in the rate and extent to which the active ingredient in pharmaceutical equivalents or pharmaceutical alternatives becomes available at the site of drug action when administrated at the same molar dose under similar conditions in a properly designed study. Two oral dosage forms are considered to be bioequivalent if both rate and extent of absorption are the same.
A Biowaiver means that in vivo bioavailability and/or bioequivalence studies may be waived (not considered necessary for product approval). Instead of conducting expensive and time consuming in vivo studies, a dissolution test could be adopted as the surrogate basis for the decision as to whether the two pharmaceutical products are equivalent.
Vesicles are colloidal particles in which a concentric bilayer made-up of amphiphilic molecules surrounds an aqueous compartment Useful vehicle for drug delivery of both hydrophobic drugs and hydrophilic drugs, which are encapsulated in the interior aqueous compartment.
Biowaiver Based on BCS Classification System: Criteria and Requirements Accor...Tareq ✅
Bioavailability (BA)/bioequivalence (BE) parameters are generally required for approval of new and generic drugs. Bioequivalence based on plasma drug concentration has become the most frequently used and successful biomarker of safety and efficacy of a drug. According to the FDA’s regulations BA is defined as the rate and extent to which the active ingredient is absorbed from a drug product and becomes available at the site of action and BE can be defined as the absence of a significant difference in the rate and extent to which the active ingredient in pharmaceutical equivalents or pharmaceutical alternatives becomes available at the site of drug action when administrated at the same molar dose under similar conditions in a properly designed study. Two oral dosage forms are considered to be bioequivalent if both rate and extent of absorption are the same.
A Biowaiver means that in vivo bioavailability and/or bioequivalence studies may be waived (not considered necessary for product approval). Instead of conducting expensive and time consuming in vivo studies, a dissolution test could be adopted as the surrogate basis for the decision as to whether the two pharmaceutical products are equivalent.
To recommend acceptable amounts for residual solvents in pharmaceuticals for the safety of the patient. The guideline recommends use of less toxic solvents and describes levels considered to be toxicologically acceptable for some residual solvents.
The guideline applies to all dosage forms and routes of administration.
This guidelines does not address all possible solvents, only those identified in drugs at that time, neither address solvents intentionally used as excipients nor solvates.
The maximum acceptable intake per day of residual solvent in pharmaceutical products is defined as “permitted daily exposure” (PDE)
Previously, another terms were used like “Tolerable daily intake” (TDI) & “Acceptable daily intake” (ADI) by different organization & authorities, but now usually this new term “PDE” is used
A pharmaceutical suspension is a heterogeneous system in which finely divided solid particles are dispersed in a liquid medium. Unlike solutions, where solutes are completely dissolved, suspensions involve particles that are only partially soluble or insoluble in the liquid. These suspensions are commonly used in the pharmaceutical industry to deliver medications that may be poorly soluble or unstable in their pure form. The solid particles, often in the form of powders or crystals, are dispersed throughout the liquid phase, creating a stable mixture through the use of suspending agents or stabilizers. These agents prevent the settling of particles, ensuring uniform distribution and ease of redispersion upon shaking before administration. Pharmaceutical suspensions offer advantages in terms of flexibility in dosing and formulation, enabling the delivery of therapeutic agents in various forms such as oral liquids, injectables, or topical preparations, enhancing patient compliance and therapeutic efficacy. The formulation and stability of pharmaceutical suspensions require careful consideration of factors such as particle size, density, and the choice of stabilizers to maintain a consistent and reliable product.
WaReS is a code developed by Marine Analytica to calculate loads and responses of floating structures. This memo presents an extract of the verification report.
To recommend acceptable amounts for residual solvents in pharmaceuticals for the safety of the patient. The guideline recommends use of less toxic solvents and describes levels considered to be toxicologically acceptable for some residual solvents.
The guideline applies to all dosage forms and routes of administration.
This guidelines does not address all possible solvents, only those identified in drugs at that time, neither address solvents intentionally used as excipients nor solvates.
The maximum acceptable intake per day of residual solvent in pharmaceutical products is defined as “permitted daily exposure” (PDE)
Previously, another terms were used like “Tolerable daily intake” (TDI) & “Acceptable daily intake” (ADI) by different organization & authorities, but now usually this new term “PDE” is used
A pharmaceutical suspension is a heterogeneous system in which finely divided solid particles are dispersed in a liquid medium. Unlike solutions, where solutes are completely dissolved, suspensions involve particles that are only partially soluble or insoluble in the liquid. These suspensions are commonly used in the pharmaceutical industry to deliver medications that may be poorly soluble or unstable in their pure form. The solid particles, often in the form of powders or crystals, are dispersed throughout the liquid phase, creating a stable mixture through the use of suspending agents or stabilizers. These agents prevent the settling of particles, ensuring uniform distribution and ease of redispersion upon shaking before administration. Pharmaceutical suspensions offer advantages in terms of flexibility in dosing and formulation, enabling the delivery of therapeutic agents in various forms such as oral liquids, injectables, or topical preparations, enhancing patient compliance and therapeutic efficacy. The formulation and stability of pharmaceutical suspensions require careful consideration of factors such as particle size, density, and the choice of stabilizers to maintain a consistent and reliable product.
WaReS is a code developed by Marine Analytica to calculate loads and responses of floating structures. This memo presents an extract of the verification report.
The International Journal of Engineering & Science is aimed at providing a platform for researchers, engineers, scientists, or educators to publish their original research results, to exchange new ideas, to disseminate information in innovative designs, engineering experiences and technological skills. It is also the Journal's objective to promote engineering and technology education. All papers submitted to the Journal will be blind peer-reviewed. Only original articles will be published.
Ijmet 08 02_029NUMERICAL SOLUTIONS FOR PERFORMANCE PREDICTION OF CENTRIFUGAL ...IAEME Publication
An attempt is made in the present study to investigate the superior turbulence model for
simulating three dimensional flows in centrifugal compressor. The strong channelled curvature and
intensive rotations prevalent in centrifugal compressor resulting high swirling and secondary flow
nictitates choosing appropriate turbulence model for accurate performance predictions. The
various turbulence models offered in FLUENT viz Spalart Allmaras (curvature correction),
Transition SST (curvature correction), Scaled Adaptive Simulations (Curvature correction with
compressibility effect), Reynolds stress model (compressibility effect) were investigated presently
for Eckardt Impeller. Reynolds stress model though involves higher computational time was found
to be the superior model. It is essential to investigate the onset of surge and choke for completely
understanding the performance of a centrifugal compressor. Choking phenomena was observed
when the speed reached 16000 rpm with relative Mach number reaching unity in the impeller
region. The maximum flow rate at 16000 rpm was 0.4 kg/s per blade and remained constant then
16500 rpm. Surging was founded to initiate when the back pressure has to reach 1.8 bar resulting
in zero discharge
NUMERICAL SOLUTIONS FOR PERFORMANCE PREDICTION OF CENTRIFUGAL COMPRESSORIAEME Publication
An attempt is made in the present study to investigate the superior turbulence model forsimulating three dimensional flows in centrifugal compressor. The strong channelled curvature andintensive rotations prevalent in centrifugal compressor resulting high swirling and secondary flownictitates choosing appropriate turbulence model for accurate performance predictions. Thevarious turbulence models offered in FLUENT viz Spalart Allmaras (curvature correction),Transition SST (curvature correction), Scaled Adaptive Simulations (Curvature correction withcompressibility effect), Reynolds stress model (compressibility effect) were investigated presentlyfor Eckardt Impeller. Reynolds stress model though involveshigher computational time was found
to be the superior model. It is essential to investigate the onset of surge and choke for completelyunderstanding the performance of a centrifugal compressor. Choking phenomena was observedwhen the speed reached 16000 rpm with relative Mach number reaching unity in the impellerregion. The maximum flow rate at 16000 rpm was 0.4 kg/s per blade and remained constant then16500 rpm. Surging was founded to initiate when the back pressure has to reach 1.8 bar resultingin zero discharge
In this paper, the unsteady motion of a spherical particle rolling down an inclined tube in a
Newtonian fluid for a range of Reynolds numbers was solved using a simulation method called
the Differential Transformation Method (DTM). The concept of differential transformation is
briefly introduced, and then we employed it to derive solution of nonlinear equation. The
obtained results for displacement, velocity and acceleration of the motion from DTM are
compared with those from numerical solution to verify the accuracy of the proposed method.
The effects of particle diameter (size), continues phase viscosity and inclination angles was
studied. As an important result it was found that the inclination angle does not affect the
acceleration duration. The results reveal that the Differential Transformation Method can achieve suitable results in predicting the solution of such problems.
Aerodynamic and Acoustic Parameters of a Coandã Flow – a Numerical Investigationdrboon
Coandã flows have been the study of aircraft designers primarily for the prospect of achieving higher lift coefficient wings. Recently the environmental problem of noise pollution attracted further interest on the matter. The approach used is numerical; the computations were made using a large eddy simulation (LES) technique coupled with a Ffowcs-Williams-Hawkings (FWH) acoustic analysis. The spectrum of the flow was measured at three locations in the vicinity of the ramp showing that the low frequency region is dominant. The findings may be used as reference for the development of quiet aircraft that use super-circulation, as it is the case with the Upper Surface Blown (USB) configurations.
Methods to determine pressure drop in an evaporator or a condenserTony Yen
This articles aims to explain how one can relatively easily calculate the pressure drop within a condenser or an evaporator, where two-phase flow occurs and the Navier-Stokes equation becomes very tedious.
Pwm Control Strategy for Controlling Of Parallel Rectifiers In Single Phase T...IJERA Editor
This paper explains that how to develop and design, control of single phase to three phase drive system. The
proposed topology of drive system consisting of two parallel connected rectifiers, inverter and induction motor,
connected through inductor and capacitor, where used to produce balanced output to the motor drive. The main
objective of this proposed method is to reduce the circulating currents and harmonic distortions at the converter
input side, here the control strategy of drive system is PWM (pulse width modulations techniques) control
strategy, the proposed topology also provides fault compensation in the case of short circuit faults and failure of
switches for uninterrupted Power supplies. We also develop and simulate the MATLAB models for proposed
drive system, by using MATLAB/ Simulink the output results simulate and observed.
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
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 leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
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. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
263778731218 Abortion Clinic /Pills In Harare ,sisternakatoto
263778731218 Abortion Clinic /Pills In Harare ,ABORTION WOMEN’S CLINIC +27730423979 IN women clinic we believe that every woman should be able to make choices in her pregnancy. Our job is to provide compassionate care, safety,affordable and confidential services. That’s why we have won the trust from all generations of women all over the world. we use non surgical method(Abortion pills) to terminate…Dr.LISA +27730423979women Clinic is committed to providing the highest quality of obstetrical and gynecological care to women of all ages. Our dedicated staff aim to treat each patient and her health concerns with compassion and respect.Our dedicated group ABORTION WOMEN’S CLINIC +27730423979 IN women clinic we believe that every woman should be able to make choices in her pregnancy. Our job is to provide compassionate care, safety,affordable and confidential services. That’s why we have won the trust from all generations of women all over the world. we use non surgical method(Abortion pills) to terminate…Dr.LISA +27730423979women Clinic is committed to providing the highest quality of obstetrical and gynecological care to women of all ages. Our dedicated staff aim to treat each patient and her health concerns with compassion and respect.Our dedicated group of receptionists, nurses, and physicians have worked together as a teamof receptionists, nurses, and physicians have worked together as a team wwww.lisywomensclinic.co.za/
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
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Minimum Torque (nN.m) Oscillation 0.5 2 10
Minimum Torque (nN.m) Steady
Shear
5 10 20
Maximum Torque (mN.m) 200 200 150
Torque Resolution (nN.m) 0.05 0.1 0.1
Minimum Frequency (Hz) 1.0E-07 1.0E-07 1.0E-07
Maximum Frequency (Hz) 100 100 100
Minimum Angular Velocity (rad/s) 0 0 0
Maximum Angular Velocity (rad/s) 300 300 300
Displacement Transducer Optical
encoder
Optical
encoder
Optical
encoder
Optical Encoder Dual Reader Standard N/A N/A
Displacement Resolution (nrad) 2 10 10
Step Time, Strain (ms) 15 15 15
Step Time, Rate (ms) 5 5 5
Normal/Axial Force Transducer FRT FRT FRT
Maximum Normal Force (N) 50 50 50
Normal Force Sensitivity (N) 0.005 0.005 0.01
Normal Force Resolution (mN) 0.5 0.5 1
,ZͲϭ
,ZͲϯ
,ZͲϮ
DHR - DMA mode (optional)
Motor Control FRT
Minimum Force (N) Oscillation 0.1
Maximum Axial Force (N) 50
Minimum Displacement (μm)
Oscillation
1.0
Maximum Displacement (μm)
Oscillation
100
Displacement Resolution (nm) 10
Axial Frequency Range (Hz) 1 x 10-5 to 16
19. TAINSTRUMENTS.COM
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Force/Torque Rebalance Transducer (Sample Stress)
Transducer Type Force/Torque
Rebalance
Transducer Torque Motor Brushless DC
Transducer Normal/Axial Motor Brushless DC
Minimum Torque (μN.m) Oscillation 0.05
Minimum Torque (μN.m) Steady Shear 0.1
Maximum Torque (mN.m) 200
Torque Resolution (nN.m) 1
Transducer Normal/Axial Force Range (N) 0.001 to 20
Transducer Bearing Groove Compensated
Air
Driver Motor (Sample Deformation)
Maximum Motor Torque (mN.m) 800
Motor Design Brushless DC
Motor Bearing Jeweled Air, Sapphire
Displacement Control/ Sensing Optical Encoder
Strain Resolution (μrad) 0.04
Minimum Angular Displacement (μrad)
Oscillation
1
Maximum Angular Displacement (μrad)
Steady Shear
Unlimited
Angular Velocity Range (rad/s) 1x 10-6 to 300
Angular Frequency Range (rad/s) 1x 10-7 to 628
Step Change, Velocity (ms) 5
Step Change, Strain (ms) 10
Orthogonal Superposition (OSP) and
DMA modes
Motor Control FRT
Minimum Transducer Force (N)
Oscillation
0.001
Maximum Transducer Force
(N)
20
Minimum Displacement (μm)
Oscillation
0.5
Maximum Displacement (μm)
Oscillation
50
Displacement Resolution (nm) 10
Axial Frequency Range (Hz) 1 x 10-5 to 16
21. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
KRRVLQJD*HRPHWU6L]H
ƒ Assess the ‘viscosity’ of your sample
ƒ When a variety of cones and plates are available, select diameter
appropriate for viscosity of sample
ƒ Low viscosity (milk) - 60mm geometry
ƒ Medium viscosity (honey) - 40mm geometry
ƒ High viscosity (caramel) – 20 or 25mm geometry
ƒ Examine data in terms of absolute instrument variables
torque/displacement/speed and modify geometry choice to move
into optimum working range
ƒ You may need to reconsider your selection after the first run!
22. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
3DUDOOHO3ODWH
Strain Constant:
Stress Constant:
(to convert angular velocity, rad/sec, to shear rate,
1/sec, at the edge or angular displacement, radians,
to shear strain (unitless) at the edge. The radius, r,
and the gap, h, are expressed in meters)
(to convert torque, N⋅m, to shear stress at the
edge, Pa, for Newtonian fluids. The radius, r, is
expressed in meters)
ŝĂŵĞƚĞƌ;Ϯ⋅
⋅
⋅
⋅ƌͿ
'ĂƉ;ŚͿ
ܭఙ ൌ ଶ
గయ
ܭఊ ൌ
28. TAINSTRUMENTS.COM
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Strain Constant:
Stress Constant:
(to convert angular velocity, rad/sec, to shear rate.
1/sec, or angular displacement, radians, to shear strain,
which is unit less. The angle, β, is expressed in radians)
(to convert torque, N⋅m, to shear stress, Pa.
The radius, r, is expressed in meters)
Truncation (gap)
ܭఊ ൌ ଵ
ఉ
ܭఙ ൌ ଷ
ଶగయ
Diameter (2⋅
⋅
⋅
⋅r)
33. TAINSTRUMENTS.COM
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× Under Filled sample:
Lower torque contribution
× Under Filled sample:
Lower torque contribution
9 Correct Filling
9 Correct Filling
× Over Filled sample:
Additional stress from
drag along the edges
× Over Filled sample:
Additional stress from
drag along the edges
× Under Filled sample:
Lower torque contribution
9 Correct Filling
× Over Filled sample:
Additional stress from
drag along the edges
34. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
RQFHQWULFOLQGHU
Strain Constant:
(to convert angular velocity, rad/sec, to shear rate,
1/sec, or angular displacement, radians, to shear
strain (unit less). The radii, r1 (inner) and r2 (outer),
are expressed in meters)
(to convert torque, N⋅m, to shear stress, Pa. The bob
length, l, and the radius, r, are expressed in meters)
Stress Constant: ܭఙ ൌ ଵ
ସగ
ݎͳ
ଶ
ݎʹ
ଶ
ݎʹ
ଶݎͳ
ଶ
ܭఊ ൌ
ݎͳ
ଶ ݎʹ
ଶ
ݎʹ
ଶݎͳ
ଶ
*Note including end correction factor. See TRIOS Help
*
35. TAINSTRUMENTS.COM
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Strain Constant:
Stress Constant:
ƒ Use for very low viscosity systems (1 mPas)
r1
r2
r3
r4
ARES Gap Settings: standard operating gap DW = 3.4 mm
narrow operating gap DW = 2.0 mm
Use equation Gap 3 × (R2 –R1)
ܭఊ ൌ
ݎͳ
ଶ ݎʹ
ଶ
ݎʹ
ଶ െݎͳ
ଶ
ܭఙ ൌ
ଵ
మାଶ
మ
ସగήଶ
మ ଵ
మାଷ
మ
h
38. TAINSTRUMENTS.COM
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7RUVLRQ5HFWDQJXODU
w = Width
l = Length
t = Thickness
Advantages:
ƒ High modulus samples
ƒ Small temperature
gradient
ƒ Simple to prepare
Disadvantages:
ƒ No pure Torsion mode for
high strains
ܭఊ ൌ
ݐ
݈ ͳ െ ͲǤ͵ͺ ௧
௪
ଶ
ܭఛ ൌ
͵ ଵǤ଼
௪
ݓ ή ݐଶ
Torsion cylindrical also available
39. TAINSTRUMENTS.COM
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ƒ Torsion and DMA geometries allow solid samples to be
characterized in a temperature controlled environment
ƒ Torsion measures G’, G”, and Tan δ
ƒ DMA measures E’, E”, and Tan δ
ƒ ARES G2 DMA is standard function (50 μm amplitude)
ƒ DMA is an optional DHR function (100 μm amplitude)
Rectangular and
cylindrical torsion
DMA 3-point bending and tension
(cantilever not shown)
40. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
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Geometry Application Advantage Disadvantage
Cone/plate fluids, melts
viscosity 10mPas
true viscosities temperature ramp difficult
Parallel Plate fluids, melts
viscosity 10mPas
easy handling,
temperature ramp
shear gradient across
sample
Couette low viscosity samples
10 mPas
high shear rate large sample volume
Double Wall Couette very low viscosity
samples 1mPas
high shear rate cleaning difficult
Torsion Rectangular solid polymers,
composites
glassy to rubbery
state
Limited by sample stiffness
DMA
Solid polymers, films,
Composites
Glassy to rubbery
state
Limited by sample stiffness
(Oscillation and
stress/strain)
43. TAINSTRUMENTS.COM
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ƒ Instrument Calibrations
ƒ Transducer
ƒ Temperature Offsets
ƒ Phase Angle (Service)
ƒ Measure Gap Temperature
Compensation
ƒ Geometry Calibrations:
ƒ Compliance and Inertia (from table)
ƒ Gap Temperature Compensation
ƒ Details in Appendix #4
44. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
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ƒ Rheometers are calibrated from the factory and again at
installation.
ƒ TA recommends routine validation or confidence checks
using standard oils or Polydimethylsiloxane (PDMS).
ƒ PDMS is verified using a 25 mm parallel plate.
ƒ Oscillation - Frequency Sweep: 1 to 100 rad/s with 5% strain at 30°C
ƒ Verify modulus and frequency values at crossover
ƒ Standard silicone oils can be verified using cone, plate or
concentric cylinder configurations.
ƒ Flow – Ramp: 0 to 88 Pa at 25°C using a 60 mm 2° cone
ƒ Service performs this test at installation
46. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
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ƒ Set Peltier temperature to 25°C and
equilibrate.
ƒ Zero the geometry gap
ƒ Load sample
ƒ Be careful not to introduce air bubbles!
ƒ Set the gap to the trim gap
ƒ Lock the head and trim with non-absorbent
tool
ƒ Important to allow time for temperature equilibration.
ƒ Go to geometry gap and initiate the
experiment.
49. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
ƒ Viscosity is…
ƒ “lack of slipperiness”
ƒ synonymous with internal friction
ƒ resistance to flow
9LVFRVLW'HILQLWLRQ
ƒ The Units of Viscosity are …
ƒ SI unit is the Pascal.second (Pa.s)
ƒ cgs unit is the Poise
ƒ 10 Poise = 1 Pa.s
ƒ 1 cP (centipoise) = 1 mPa.s (millipascal second)
56. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
time
Viscosity
Thixotropic
Rheopectic
Shear Rate = Constant
1RQ1HZWRQLDQ7LPH'HSHQGHQW)OXLGV
ƒ Rheopectic materials
become more viscous
with increasing time of
applied force
ƒ Higher concentration
latex dispersions and
plastisol paste materials
exhibit rheopectic
behavior
ƒ Thixotropic materials
become more fluid with
increasing time of applied
force
ƒ Coatings and inks can
display thixotropy when
sheared due to structure
breakdown
60. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
ƒ Stress is applied to
material at a constant
rate. Resultant strain
is monitored with time.
time (min)
m =Stress rate
(Pa/min)
Deformation
USES
ƒ Yield stress
ƒ Scouting Viscosity Run
RQWLQXRXV5DPS
63. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
0.5000
0 0.1000 0.2000 0.3000 0.4000
shear rate (1/s)
500.0
0
100.0
200.0
300.0
400.0
shear
stress
(Pa)
TA Instruments
FORDB3.04F-Up step
FORDB3.04F-Down step
FORDB3.05F-Up step
FORDB3.05F-Down step
Run in Stress Control
ZĞĚ͗ŝƌƐƚĐLJĐůĞ
ůƵĞ͗^ĞĐŽŶĚĐLJĐůĞ
8S 'RZQ)ORZXUYHV 5HSHDWV
64. TAINSTRUMENTS.COM
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Deformation
time
Delay time
Steady State Flow
γ or σ = Constant
time
ƒ Stress is applied to sample.
Viscosity measurement is taken
when material has reached steady
state flow. The stress is
increased(logarithmically) and the
process is repeated yielding a
viscosity flow curve.
USES
ƒ Viscosity Flow Curves
ƒ Yield Stress Measurements
σ
Žƌ
ߛሶ
σ
Žƌ
ߛሶ
6WHSSHGRU6WHDG6WDWH)ORZ
Data point saved
65. TAINSTRUMENTS.COM
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ƒ A series of logarithmic stress steps allowed to reach steady state, each
one giving a single viscosity data point:
Shear
Thinning
Region
Shear Rate, 1/s
Viscosity
Time
η = σ / γ/
(d dt)
6WHSSHGRU6WHDG6WDWH)ORZ
Data at each
Shear Rate
68. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
1000
0.1000 1.000 10.00 100.0
shear rate (1/s)
0.8000
0
0.1000
0.2000
0.3000
0.4000
0.5000
0.6000
0.7000
viscosity
(Pa.s)
^ĂŵƉůĞϭͲůŽǁƐƚĞƉ
^ĂŵƉůĞϮͲůŽǁƐƚĞƉ
Which material would do a better job
coating your throat?
RPSDULVRQRIRXJK6UXSV
69. TAINSTRUMENTS.COM
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1000
1.000E-4 1.000E-3 0.01000 0.1000 1.000 10.00 100.0
shear rate (1/s)
10000
0.1000
1.000
10.00
100.0
1000
viscosity
(Pa.s)
A.01F-Flow step
B.01F-Flow step
High shear rates BA
Low shear rates BA
Medium shear rates AB
RPSDULVRQRI7ZR/DWH[3DLQWV
70. TAINSTRUMENTS.COM
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ƒ Hold the rate or stress
constant whilst
ramping the
temperature.
time (min)
USES
ƒ Measure the viscosity change vs. temperature
y y y y
)ORZ7HPSHUDWXUH5DPS
71. TAINSTRUMENTS.COM
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Notice a nearly 2 decade decrease in viscosity. This displays the importance of
thermal equilibration of the sample prior to testing.
i.e. Conditioning Step or equilibration time for 3 to 5 min
9LVFRVLW7HPSHUDWXUH'HSHQGHQFH
72. TAINSTRUMENTS.COM
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ƒ Small gaps give high shear rates
ƒ Be careful with small gaps:
ƒ Gap errors (gap temperature compensation) and shear
heating can cause large errors in data.
ƒ Recommended gap is between 0.5 to 2.0 mm.
ƒ Secondary flows can cause increase in viscosity curve
ƒ Be careful with data interpretation at low shear rates
ƒ Surface tension can affect measured viscosity, especially
with aqueous materials
74. TAINSTRUMENTS.COM
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ƒ Wall slip can manifest as “apparent double yielding”
ƒ Can be tested by running the same test at different gaps
ƒ For samples that don’t slip, the results will be independent of the gap
76. TAINSTRUMENTS.COM
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ƒ Edge Failure – Sample leaves gap because of normal
forces
ƒ Look at stress vs. shear rate curve – stress should not
decrease with increasing shear rate – this indicates sample
is leaving gap
ƒ Possible Solutions:
ƒ use a smaller gap or smaller angle so that you get the same
shear rate at a lower angular velocity
ƒ if appropriate (i.e. Polymer melts) make use of Cox Merz
Rule
( ) ( )
ω
η
γ
η *
≡
83. TAINSTRUMENTS.COM
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9LVFRHODVWLFLW'HILQHG
Range of Material Behavior
Liquid Like---------- Solid Like
Ideal Fluid ----- Most Materials -----Ideal Solid
Purely Viscous ----- Viscoelastic ----- Purely Elastic
Viscoelasticity: Having both viscous
and elastic properties
ƒ Materials behave in the linear manner, as described by Hooke and
Newton, only on a small scale in stress or deformation.
84. TAINSTRUMENTS.COM
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ƒ Long deformation time: pitch behaves
like a highly viscous liquid
ƒ 9th drop fell July 2013
ƒ Short deformation time: pitch behaves
like a solid
ŚƚƚƉ͗ͬͬǁǁǁ͘ƚŚĞĂƚůĂŶƚŝĐ͘ĐŽŵͬƚĞĐŚŶŽůŽŐLJͬĂƌĐŚŝǀĞͬϮϬϭϯͬϬϳͬƚŚĞͲϯͲŵŽƐƚͲĞdžĐŝƚŝŶŐͲǁŽƌĚƐͲŝŶͲƐĐŝĞŶĐĞͲƌŝŐŚƚͲŶŽǁͲƚŚĞͲƉŝƚĐŚͲĚƌŽƉƉĞĚͬϮϳϳϵϭϵͬ
Started in 1927 by Thomas Parnell in Queensland, Australia
86. TAINSTRUMENTS.COM
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ƒ Silly Putties have different characteristic relaxation times
ƒ Dynamic (oscillatory) testing can measure time-dependent
viscoelastic properties more efficiently by varying frequency
(deformation time)
7LPH'HSHQGHQW9LVFRHODVWLF%HKDYLRU
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ƒ Old Testament Prophetess who said (Judges 5:5):
The Mountains ‘Flowed’ before the Lord
ƒ Everything Flows if you wait long enough!
ƒ Deborah Number, De - The ratio of a characteristic
relaxation time of a material (τ) to a characteristic time of
the relevant deformation process (T).
Ğсτͬd
88. TAINSTRUMENTS.COM
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ƒ Hookean elastic solid - IJ is infinite
ƒ Newtonian Viscous Liquid - IJ is zero
ƒ Polymer melts processing - IJ may be a few seconds
High De Solid-like behavior
Low De Liquid-like behavior
IMPLICATION: Material can appear solid-like because
1) it has a very long characteristic relaxation time or
2) the relevant deformation process is very fast
90. TAINSTRUMENTS.COM
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If the deformation is small, or applied sufficiently slowly,
the molecular arrangements are never far from
equilibrium.
The mechanical response is then just a reflection of
dynamic processes at the molecular level which go on
constantly, even for a system at equilibrium.
This is the domain of LINEAR VISCOELASTICITY.
The magnitudes of stress and strain are related
linearly, and the behavior for any liquid is completely
described by a single function of time.
Mark, J., et. al., Physical Properties of Polymers, American Chemical Society, 1984, p. 102.
95. TAINSTRUMENTS.COM
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ƒ Time to complete one oscillation
ƒ Frequency is the inverse of time
ƒ Units
ƒ Angular Frequency = radians/second
ƒ Frequency = cycles/second (Hz)
ƒ Rheologist must think in terms of rad/s.
ƒ 1 Hz = 6.28 rad/s
101. TAINSTRUMENTS.COM
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ƒ The stress in a dynamic experiment is referred to as the
complex stress σ*
Phase angle δ
δ
δ
δ
Complex Stress, σ
σ
σ
σ*
Strain, ε
ε
ε
ε
σ
σ
σ
σ* = σ
σ
σ
σ' + iσ
σ
σ
σ
ƒ The complex stress can be separated into two components:
1) An elastic stress in phase with the strain. σ
σ
σ
σ' = σ
σ
σ
σ*cosδ
δ
δ
δ
σ' is the degree to which material behaves like an elastic solid.
2) A viscous stress in phase with the strain rate. σ
σ
σ
σ = σ
σ
σ
σ*sinδ
δ
δ
δ
σ is the degree to which material behaves like an ideal liquid.
The material functions can be described in
terms of complex variables having both real and
imaginary parts. Thus, using the relationship:
Complex number: ݔ ݅ݕ ൌ ݔଶ ݕଶ
102. TAINSTRUMENTS.COM
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9LVFRHODVWLF3DUDPHWHUV
The Elastic (Storage) Modulus:
Measure of elasticity of material.
The ability of the material to store
energy.
The Viscous (loss) Modulus:
The ability of the material to
dissipate energy. Energy lost as
heat.
The Modulus: Measure of
materials overall resistance to
deformation.
Tan Delta:
Measure of material damping -
such as vibration or sound
damping.
ᇱ
ൌ ୗ୲୰ୣୱୱכ
ୗ୲୰ୟ୧୬
‘• Ɂ
̶
ൌ ୗ୲୰ୣୱୱכ
ୗ୲୰ୟ୧୬
•‹ Ɂ
כ
ൌ ୗ୲୰ୣୱୱכ
ୗ୲୰ୟ୧୬
–ƒ Ɂ ൌ ୋ̶
ୋᇱ
104. TAINSTRUMENTS.COM
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ƒ The viscosity measured in an oscillatory experiment is a Complex
Viscosity much the way the modulus can be expressed as the
complex modulus. The complex viscosity contains an elastic
component and a term similar to the steady state viscosity.
ƒ The Complex viscosity is defined as:
Ș* = Ș’ + i Ș”
or
Ș* = G*/Ȧ
Note: frequency must be in rad/sec!
105. TAINSTRUMENTS.COM
TAINSTRUMENTS.COM
Parameter Shear Elongation Units
Strain ɶ сɶϬƐŝŶ;ʘƚͿ ɸ сɸϬ ƐŝŶ;ʘƚͿ ---
Stress σ сσϬƐŝŶ;ʘƚнɷͿ τ сτϬƐŝŶ;ʘƚнɷͿ Pa
Storage Modulus
(Elasticity)
'͛с;σϬͬɶϬͿĐŽƐɷ ͛с;τϬͬɸϬͿĐŽƐɷ Pa
Loss Modulus
(Viscous Nature)
'͟с;σϬͬɶϬͿƐŝŶɷ ͟с;τϬͬɸϬͿƐŝŶɷ Pa
Tan į 'ͬ͟'͛ ͬ͛͟ ---
Complex Modulus 'Ύ с;'͛Ϯн'͟ϮͿϬ͘ϱ Ύ с;͛Ϯн͟ϮͿϬ͘ϱ
Pa
Complex Viscosity ηΎ с'Ύͬʘ η
Ύ сΎͬʘ Pa·sec
Cox-Merz Rule for Linear Polymers: η*(Ȧ) = η(ߛሶ) @ ߛሶ = Ȧ
'QDPLF5KHRORJLFDO3DUDPHWHUV
107. TAINSTRUMENTS.COM
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ƒ The material response to
increasing deformation
amplitude (strain or
stress) is monitored at a
constant frequency and
temperature.
Time
Stress
or
strain
ƒ Main use is to determine LVR
ƒ All subsequent tests require an amplitude found in the LVR
ƒ Tests assumes sample is stable
ƒ If not stable use Time Sweep to determine stability
111. TAINSTRUMENTS.COM
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Linear response to a sinusoidal excitation
is sinusoidal and represented by the
fundamental in the frequency domain
Nonlinear response to a sinusoidal
excitation is not sinusoidal and
represented in the frequency domain by
the fundamental and the harmonics
113. TAINSTRUMENTS.COM
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ƒ The material response
is monitored at a
constant frequency,
amplitude and
temperature.
USES
ƒ Time dependent Thixotropy
ƒ Cure Studies
ƒ Stability against thermal degradation
ƒ Solvent evaporation/drying
Time
Stress
or
strain
114. TAINSTRUMENTS.COM
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ƒ Important, but often overlooked
ƒVisually observe the sample
ƒ Determines if properties are changing over the time of
testing
ƒ Complex Fluids or Dispersions
ƒ Preshear or effects of loading
ƒ Drying or volatilization (use solvent trap)
ƒ Thixotropic or Rheopectic
ƒ Polymers
ƒ Degradation (inert purge)
ƒ Crosslinking
117. TAINSTRUMENTS.COM
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175.0
0 25.00 50.00 75.00 100.0 125.0 150.0
time (s)
100.0
10.00
G'
(Pa)
Sample “A” time sweep
100.0
0.1000 1.000 10.00
osc. stress (Pa)
100.0
10.00
Delay after pre-shear = 0 sec
Delay after pre-shear = 150 sec
Pre-shear conditions:
100 1/s for 30 seconds
ƒ End of LVR is indicative of “Yield” or “Strength of Structure”
ƒ Useful for Stability predictions (stability as defined by yield)
,PSRUWDQFHRI:DLWLQJIRU6WUXFWXUH5HEXLOG
120. TAINSTRUMENTS.COM
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ƒ The material response to
increasing frequency (rate of
deformation) is monitored at
a constant amplitude (strain
or stress) and temperature.
ŵƉůŝƚƵĚĞ
dŝŵĞ
ƒ Strain should be in LVR
ƒ Sample should be stable
ƒ Remember – Frequency is 1/time so low frequencies
will take a long time to collect data – i.e. 0.001Hz is
1000 sec (over 16 min)
125. TAINSTRUMENTS.COM
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ƒ DHR has a combined motor and transducer design.
ƒ In an DHR rheometer, the applied motor torque and
the measured amplitude are coupled.
ƒ The moment of inertia required to move the motor and
geometry (system inertia) is coupled with the angular
displacement measurements.
ƒ This means that BOTH the system inertia and the
sample contributes to the measured signal.
127. TAINSTRUMENTS.COM
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ƒ Inertia consideration
ƒ Viscosity limitations with frequency
ƒ Minimize inertia by using low mass geometries
ƒ Monitor inertia using Raw Phase in degree
ƒ When Raw Phase is greater than:
ƒ 150°
°
°
° degrees for AR series
ƒ 175°
°
°
° degrees for DHR series
ƒ This indicates that the system inertia is dominating the
measurement signal. Data may not be valid
Raw Phase × Inertia Correction = delta
128. TAINSTRUMENTS.COM
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Waveforms at high frequencies
Access to raw phase angle
only available with TA
Instruments Rheometers!
Access to raw phase angle
only available with TA
Instruments Rheometers!
Negligible correction at low frequencies
Inertial effects at
high frequencies
129. TAINSTRUMENTS.COM
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ƒ ARES-G2 has a separate motor and transducer
design.
ƒ In an ARES-G2, the motor applies the deformation
independent of the torque measurement on the transducer.
ƒ The moment of inertia required to move the motor is
decoupled from the torque measurements.
ƒ This means the motor inertia does not contribute to the test
results.
ƒ Benefits of ARES-G2:
ƒ System inertia free
ƒ Capable of running low viscosity samples up to high
frequency
131. TAINSTRUMENTS.COM
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ƒ A linear heating rate is
applied. The material
response is monitored at a
constant frequency and
constant amplitude of
deformation. Data is taken
at user defined time
intervals.
Temperature
(°
C)
time (min)
Denotes Oscillatory
Measurement
time between
data points
m = ramp rate
(°
C/min)
132. TAINSTRUMENTS.COM
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ƒ A step and hold temperature
profile is applied. The
material response is
monitored at one, or over a
range of frequencies, at
constant amplitude of
deformation.
– No thermal lag Time
Soak
Time
Step Size
Oscillatory
Measurement
Time
Step Size
Oscillatory
Measurement
Soak
Time
134. TAINSTRUMENTS.COM
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ƒ Solid in torsion rectangular
ƒ Look at Tg, secondary transitions and study structure-
property relationships of finished product.
ƒ Themosetting polymers
ƒ Follow curing reactions
ƒ Polymer melts and other liquids
ƒ Measure temperature dependence of viscoelastic
properties
136. TAINSTRUMENTS.COM
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ƒ It is important to setup normal force control during any temperature
change testing or curing testing
ƒ Some general suggestions for normal force control
ƒ For torsion testing, set normal force in tension: 1-2N ± 0.5-1.0N
ƒ For curing or any parallel plate testing, set normal force in
compression: 0 ± 0.5N
139. TAINSTRUMENTS.COM
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ƒ Cures are perhaps the most challenging experiments to conduct on
rheometers as they challenge all instrument specifications both high
and low.
ƒ The change in modulus as a sample cures can be as large as 7-8
decades and change can occur very rapidly.
ƒ AR, DHR, and ARES instruments have ways of trying to cope with
such large swings in modulus
ƒ AR: Non-iterative sampling (w/ Axial force control)
ƒ DHR: Non-iterative sampling (w/ Axial force control) and
Auto-strain (w/ Axial force active) in TRIOS v3.2 or higher
ƒ ARES: Auto-strain (w/ Axial force or auto-tension active)
XUHRU7KHUPRVHW0DWHULDOV
140. TAINSTRUMENTS.COM
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7KHUPRVHWWLQJ3ROPHUV
η
Žƌ
'͛
Time
dĞŵƉ
At start of test have a material that starts as
liquid, paste, pressed power Pellet, or prepreg
As the temp increases
the viscosity of resin
decreases
Crosslinking
reaction causes
h and G’ to increase
Material hits minimum viscosity which depends on
Max temperature, frequency, ramp rate and may depend
on strain or stress amplitude
Material fully cured
Maximum h or G’ reached
141. TAINSTRUMENTS.COM
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ƒNon-Iterative Sampling – motor
torque is adjusted based on
previous stress value and predicts
new value required to obtain the
target strain (good for rapid
measurements)
ƒPrecision Sampling – motor torque
is adjusted at the end of an
oscillation cycle in order to reach
commanded strain
ƒContinuous Oscillation (direct
strain)* – motor torque is adjusted
during the oscillation cycle to apply
the commanded strain
*Continuous oscillation only available with DHR-2 and DHR-3
148. TAINSTRUMENTS.COM
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ƒ Strain
ƒ Depends on sample
ƒ Verify the LVR in the cured state ( e.g. 0.05%)
ƒ Normal force control or auto-tension
ƒ Requires active to adjust for sample shrinkage and/or thermal
expansion in parallel plates
ƒ Temperature
ƒ Isothermal
ƒ Fast ramp + isotherm: the fastest ramp rate
ƒ Continuous ramp rate: 3 – 5 °
C/min.
ƒ Frequency
ƒ Typically 1Hz (6.28 rad/s), 10 rad/s or higher
152. TAINSTRUMENTS.COM
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Response of ViscoElastic Material
ƒ For small deformations (strains within the linear region)
the ratio of stress to strain is a function of time only.
ƒ This function is a material property known as the
STRESS RELAXATION MODULUS, G(t)
G(t) = σ
σ
σ
σ(t)/γ
γ
γ
γ
Stress decreases with time
starting at some high value
and decreasing to zero.
time
Ϭ
155. TAINSTRUMENTS.COM
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ƒ Research Approach, such as generation of a family of
curves for TTS, then the strain should be in the linear
viscoelastic region. The stress relaxation modulus will be
independent of applied strain (or will superimpose) in the
linear region.
ƒ Application Approach, mimic real application. Then the
question is what is the range of strain that I can apply on
the sample? This is found by knowing the Strain range
the geometry can apply.
ƒ The software will calculated this for you.
γ сγ п θ ;йγ с γ п ϭϬϬͿ
157. TAINSTRUMENTS.COM
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ƒ Stress is applied to sample instantaneously, t1, and held
constant for a specific period of time. The strain is
monitored as a function of time (γ(t) or ε(t))
ƒ The stress is reduced to zero, t2, and the strain is
monitored as a function of time (γ(t) or ε(t))
ƒ Native mode on AR (1 msec)
Stress
time
t1 t2
163. TAINSTRUMENTS.COM
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UHHS5HFRYHUUHHSDQG5HFRYHUDEOHRPSOLDQFH
Mark, J., et. al., Physical Properties of Polymers, American Chemical Society, 1984, p. 102.
:;ƚͿ
ϭͬη
time
Creep Zone
:
ƌ
;ƚͿ
time
Recovery Zone
Creep Compliance Recoverable Compliance
୰ – ൌ
ɀ୳ െ ɀ –
ɐ
Where γu = Strain at unloading
γ(t) = time dependent
recoverable strain
– ൌ
ஓሺ୲ሻ
Je = Equilibrium recoverable compliance
more elastic
:Ğ
The material property obtained from
Creep experiments:
Compliance = 1/Modulus (in a sense)
164. TAINSTRUMENTS.COM
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• The ringing oscillations can be rather short-lived and may not be apparent unless using log time scale.
• The sudden acceleration, together with the measurement system’s inertia, causes a strain overshoot. For
viscoelastic materials, this can result in viscoelastic ringing, where the material undergoes a damped
oscillation just like a bowl of Jell-o when bumped.
Creep ringing in rheometry or how to deal with oft-discarded data in step stress tests!
RH Ewoldt, GH McKinley - Rheol. Bull, 2007
165. TAINSTRUMENTS.COM
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ƒ Stress is controlled by closing the loop around the sample Æ
requires optimization of control PID parameters
ƒ Pretest to determine material’s response and PID Constants
DĂƚĞƌŝĂůƌĞƐƉŽŶƐĞ
W/ ŵŽƚŽƌ
Zd ƐĂŵƉůĞ
σĐŵĚ;ƚͿ
ŝŶƚĞŐƌĂƚŽƌ
/ŶŶĞƌ
DŽƚŽƌWŽƐŝƚŝŽŶŽŽƉ
θ;ƚͿ
ŝŶĞĂƌƌĞƐƉŽŶƐĞ
σ;ƚͿ
Δσ;ƚͿ θ;ƚͿ
169. TAINSTRUMENTS.COM
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ƒ Application Approach - If you are doing creep on a solid,
you want to know the dimension change with time under a
specified stress and temperature, then the questions is
what is the max/min stress that I can apply to the
sample?. This is found by knowing the Stress range the
geometry can apply.
ƒ The software will calculated this for you.
ƒ Research Approach - If you are doing creep on a polymer
melt, and are interested in viscoelastic information (creep
and recoverable compliance), then you need to conduct the
test at a stress within the linear viscoelastic region of the
material.
σ = Kσ x Μ
'HWHUPLQLQJ6WUHVV)RUUHHS([SHULPHQW
171. TAINSTRUMENTS.COM
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Three main reasons for rheological testing:
ƒ Characterization
MW, MWD, formulation, state of flocculation, etc.
ƒ Process performance
Extrusion, blow molding, pumping, leveling, etc.
ƒ Product performance
Strength, use temperature, dimensional stability, settling
stability, etc.
3XUSRVHRID5KHRORJLFDO0HDVXUHPHQW
172. TAINSTRUMENTS.COM
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3ROPHU7HVWLQJDQG5KHRORJ
Molecular Structure
ƒ MW and MWD
ƒ Chain Branching and Cross-linking
ƒ Interaction of Fillers with Matrix Polymer
ƒ Single or Multi-Phase Structure
Viscoelastic Properties
As a function of:
ƒ Strain Rate(frequency)
ƒ Strain Amplitude
ƒ Temperature
Processability Product Performance
173. TAINSTRUMENTS.COM
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Material Property
Composites, Thermosets Viscosity, Gelation, Rate of Cure, Effect of
Fillers and Additives
Cured Laminates Glass Transition, Modulus Damping, impact
resistance, Creep, Stress Relaxation, Fiber
orientation, Thermal Stability
Thermoplastics Blends, Processing effects, stability of
molded parts, chemical effects
Elastomers Curing Characteristics, effect of fillers,
recovery after deformation
Coating, Adhesives Damping, correlations, rate of degree of
cure, glass transition temperature, modulus
174. TAINSTRUMENTS.COM
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0RVWRPPRQ([SHULPHQWVRQ3ROPHUV
ƒ Oscillation/Dynamic
ƒ Time Sweep
ƒ Degradation studies, stability for subsequent testing
ƒ Strain Sweep – Find LVER
ƒ Frequency Sweep – G’, G”, η*
ƒ Sensitive to MW/MWD differences melt flow can not see
ƒ Temperature Ramp/Temperature Step
ƒ Transitions, viscosity changes
ƒ TTS Studies
ƒ Flow/Steady Shear
ƒ Viscosity vs. Shear Rate Plots
ƒ Find Zero Shear Viscosity
ƒ Low shear information is sensitive to MW/MWD differences melt flow
can not see
ƒ Creep and Recovery
ƒ Creep Compliance/Recoverable Compliance
ƒ Very sensitive to long chain tails
175. TAINSTRUMENTS.COM
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Determines if properties
are changing over the
time of testing
ƒ Degradation
ƒ Molecular weight
building
ƒ Crosslinking
-2 0 2 4 6 8 10 12 14 16 18
10
4
10
5
-2 0 2 4 6 8 10 12 14 16 18
175
200
225
250
275
Temperature stability
good
poor
Modulus
G'
[Pa]
Time t [min]
Polyester Temperature stability
Temperature
T
[°
C]
Important, but often overlooked!
3ROPHU0HOW7KHUPDO6WDELOLW
176. TAINSTRUMENTS.COM
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,GHDOL]HG)ORZXUYH² 3ROPHU0HOWV
1.00
1.00E-5 1.00E-4 1.00E-3 0.0100 0.100
shear rate (1/s)
10.00 100.00 1000.00 1.00E4 1.00E5
log
η
Molecular Structure Compression Molding Extrusion Blow and Injection Molding
η0 = Zero Shear Viscosity
η0 = K x MW 3.4
Measure in Flow Mode
Extend Range
with Oscillation
Cox-Merz
Extend Range
with Time-
Temperature
Superposition (TTS)
Cox-Merz
First Newtonian Plateau
Second Newtonian
Plateau
Power Law Region
1.00
1.00E-5 1.00E-4 1.00E-3 0.0100 0.100
shear rate (1/s)
10.00 100.00 1000.00 1.00E4 1.00E5
log
η
Molecular Structure Compression Molding Extrusion Blow and Injection Molding
η0 = Zero Shear Viscosity
η0 = K x MW 3.4
Measure in Flow Mode
Extend Range
with Oscillation
Cox-Merz
Extend Range
with Time-
Temperature
Superposition (TTS)
Cox-Merz
First Newtonian Plateau
Second Newtonian
Plateau
Power Law Region
184. TAINSTRUMENTS.COM
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Blue-labled sample shows a rough surface after extrusion
ƒ Surface roughness
correlates with G‘ or
elasticity → broader
MWD or tiny
amounts of a high
MW component
0.1 1 10 100
10
3
10
4
10
5
10
3
10
4
10
5
T = 220
o
C
Complex
viscosity
η
*
[Pa
s]
G' rough surface
G' smooth surface
η* rough surface
η* smooth surface
HDPE pipe surface defects
Modulus
G'
[Pa]
Frequency ω [rad/s]
185. TAINSTRUMENTS.COM
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7DFNDQG3HHORI$GKHVLYHV
0.1 1 10
10
3
10
4
Tack and Peel performance of a PSA
peel
tack
good tack and peel
Bad tack and peel
Storage
Modulus
G'
[Pa]
Frequency ω [rad/s]
ƒ Bond strength is
obained from peel
(fast) and tack
(slow) tests
ƒ It can be related to
the viscoelastic
properties at
different
frequencies
Tack and peel have to be balanced for an ideal adhesive
187. TAINSTRUMENTS.COM
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ƒ Non linear effects
can be detected in
recovery before
they are seen in the
creep (viscosity
dominates)
0.1 1 10 100 1000
10
-5
10
-4
10
-3
10
-2
10
-1
10
-5
10
-4
10
-3
10
-2
10
-1
slope 1
increasing
stress
LDPE Melt
T=140
o
C
Recoverable
Compliance
Jr(t)
[1/Pa]
10 Pa
50 Pa
100 Pa
500 Pa
1000 Pa
5000 Pa
LDPE Melt creep recovery
Compliance
J(t)
[1/Pa]
Time t [s]
UHHS DQG5HFRYHUZLWK,QFUHDVLQJ6WUHVV
188. TAINSTRUMENTS.COM
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(IIHFWRI)LOOHURQ0HOW9LVFRVLW
1E-5 1E-4 1E-3 0.01 0.1 1 10 100 1000 10000
10
2
10
3
10
4
10
5
10
6
10
7
.
.
Temperature 180
o
C
LDPE filled
LDPE neat
Neat and Filled LDPE
Viscosity
η
(
γ
)
[Pa
s]
Shear rate γ [1/s]
ƒ ŝůůĞƌƐŝŶĐƌĞĂƐĞƚŚĞ
ŵĞůƚǀŝƐĐŽƐŝƚLJ
ƒ ƵĞƚŽŝŶƚĞƌͲƉĂƌƚŝĐůĞ
ŝŶƚĞƌĂĐƚŝŽŶƐ͕ƚŚĞ
ŶŽŶͲEĞǁƚŽŶŝĂŶ
ƌĂŶŐĞŝƐĞdžƚĞŶĚĞĚƚŽ
ůŽǁƐŚĞĂƌƌĂƚĞƐĂŶĚ
ƚŚĞnjĞƌŽƐŚĞĂƌ
ǀŝƐĐŽƐŝƚLJŝŶĐƌĞĂƐĞƐ
ĚƌĂŵĂƚŝĐĂůůLJ
The material has a yield, when rate and viscosity are
inverse proportional at low rate.
190. TAINSTRUMENTS.COM
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ƒ Application to processing: many processing flows are
elongation flows - testing as close as possible to
processing conditions (spinning, coating, spraying)
ƒ Relation to material structure: non linear elongation
flow is more sensitive for some structure elements
than shear flows (branching, polymer architecture)
ƒ Testing of constitutive equations: elongation results in
addition to shear data provide a more general picture
for developing material equations
194. TAINSTRUMENTS.COM
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7KHUPRVHWV$QDOVLV
ƒ Monitor the curing process
ƒViscosity change as function of time or temperature
ƒ Gel time or temperature
ƒ Test methods for monitoring curing
ƒTemperature ramp
ƒIsothermal time sweep
ƒCombination profile to mimic process
ƒ Analyze cured material’s mechanical properties (G’,
G”, tan δ , Tg etc.)
196. TAINSTRUMENTS.COM
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ƒ Molecular weight Mw goes to infinity
ƒ System loses solubility
ƒ Zero shear viscosity goes to infinity
ƒ Equilibrium Modulus is zero and starts to rise
to a finite number beyond the gel point
Note: For most applications, gel point can be
considered as when G’ = G” and tan δ = 1
199. TAINSTRUMENTS.COM
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$WWKH*HO3RLQWRQWLQXHG«
• The process of viscosity increasing takes place in two
stages: the gelation process (frequency independent) and
vitrification (related to the network Tg relative to cure
temperature and is frequency dependent).
• When you look at an isothermal cure at a constant
frequency the modulus crossover point has both the
information of gelation and vitrification.
ƒ To avoid this, run multiple isothermal runs at different
frequencies and plot the cross over in tan delta. This is the
frequency independent gel point.
‹ Alternatively, use a single mutliwave test
204. TAINSTRUMENTS.COM
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ƒ Glass transition
ƒ Secondary transitions
ƒ Crystallinity
ƒ Molecular weight/cross-linking
ƒ Phase separation (polymer blends, copolymers,...)
ƒ Composites
ƒ Aging (physical and chemical)
ƒ Curing of networks
ƒ Orientation
ƒ Effect of additives
Reference: Turi, Edith, A, Thermal Characterization of Polymeric Materials, Second Edition, Volume I., Academic Press, Brooklyn, New
York, P. 489.
3ROPHU6WUXFWXUH3URSHUWKDUDFWHUL]DWLRQ
205. TAINSTRUMENTS.COM
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G' Onset: Occurs at lowest temperature - Relates to
mechanical failure
+RZWR0HDVXUH*ODVV7UDQVLWLRQ
Reference: Turi, Edith, A, Thermal Characterization of Polymeric Materials, Second Edition, Volume I., Academic Press, Brooklyn, New York, P. 980.
tan δ
δ
δ
δ Peak: Occurs at highest temperature - used
historically in literature - a good measure of the leatherlike
midpoint between the glassy and rubbery states - height
and shape change systematically with amorphous content.
G Peak: Occurs at middle temperature - more closely
related to the physical property changes attributed to the
glass transition in plastics. It reflects molecular processes -
agrees with the idea of Tg as the temperature at the onset
of segmental motion.
206. TAINSTRUMENTS.COM
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3DVWDRRNHGLQ7RUVLRQ,PPHUVLRQ
0 10.0 20.0 30.0 40.0 50.0 60.0
time global (min)
1.000E5
1.000E6
1.000E7
1.000E8
1.000E9
1.000E10
G'
(Pa)
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
temperature
(°
C)
Addition of Water
Isotherm with
water at 22 °
C
Temperature
ramp to 95 °
C
Isotherm
with water
at 95 °
C
time (min)
G’
(Pa)
ƒ Allows samples to be
characterized while fully
immersed in a temperature
controlled fluid using Peltier
Concentric Cylinder Jacket
ƒ Track changes in mechanical
properties such as swelling or
plasticizing
207. TAINSTRUMENTS.COM
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7HVWLQJ6ROLGVRQD5KHRPHWHU
ƒ Torsion and DMA geometries allow solid samples to be
characterized in a temperature controlled environment
– DMA functionality is standard with ARES G2 and optional DHR
Rectangular and
cylindrical torsion
DMA 3-point bending and tension
(Cantilever not shown)
Modulus: G’, G”, G* Modulus: E’, E”, E*
сϮ';ϭнʆͿ ʆ ͗WŽŝƐƐŽŶ͛ƐƌĂƚŝŽ
209. TAINSTRUMENTS.COM
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Glass Transition - Cooperative motion among a large number of
chain segments, including those from neighboring polymer chains
Secondary Transitions
ƒ Local main-chain motion - intramolecular rotational motion of
main chain segments four to six atoms in length
ƒ Side group motion with some cooperative motion from the main
chain
ƒ Internal motion within a side group without interference from
side group
ƒ Motion of or within a small molecule or diluent dissolved in the
polymer (e.g. plasticizer)
7KH*ODVV 6HFRQGDU7UDQVLWLRQV
Reference: Turi, Edith, A, Thermal Characterization of Polymeric Materials, Second Edition, Volume I.,
Academic Press, Brooklyn, New York, P. 487.
215. TAINSTRUMENTS.COM
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Reference:Barnes, H.A., Hutton, J.F., and Walters, K., An Introduction to Rheology,
Elsevier Science B.V., 1989. ISBN 0-444-87469-0
log η
log ߛሶ
First
Newtonian
Plateau
Power-Law
Shear Thinning
Second
Newtonian
Plateau
Possible
Increase in
Viscosity
*HQHUDO9LVFRVLWXUYHIRU6XVSHQVLRQV
σ ∝ ߛሶm or, equivalently, η ∝ ߛሶm-1
m is usually 0.15 to 0.6
This viscosity is often called
the Zero Shear Viscosity, η0,
or the Newtonian Viscosity
218. TAINSTRUMENTS.COM
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Ϭ ϮϬϬ ϰϬϬ ϲϬϬ ϴϬϬ ϭϬϬϬ
Ϭ
ϱϬ
ϭϬϬ
ϭϱϬ
ϮϬϬ
ϮϱϬ
Time (s)
G'
(Pa)
Fast Linear Close
Exponential Close
RPSDULVRQRI/LQHDUDQG([SRQHQWLDOORVLQJ
Lowering the gap can introduce shear, breaking down weakly structured samples
Reducing the gap closure speed can minimize this effect
219. TAINSTRUMENTS.COM
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8VLQJ3UH6KHDULQJ
ƒ Monitor the viscosity signal during the pre-shear to
determine if the rate and duration are appropriate
ƒ If the viscosity is increasing during the pre-shear, the sample is
rebuilding. The pre-shear should be higher than the shear
introduced during loading to erase sample loading history
ƒ The viscosity should decrease and then level off
ƒ Typical Pre-Shear: 1- 100 sec-1, 30-60 seconds
ƒ Use an amplitude sweep to determine what strain to use
for time sweep
ƒ A high strain will break down the sample, and not allow rebuilding
ƒ A low strain will give a weak signal
ƒ Based on the Time Sweep, determine an appropriate
equilibration time for that sample
220. TAINSTRUMENTS.COM
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ƒ The goal for pre-shear is to remove the sample history at loading
ƒ For high viscosity sample, use low rate (10 1/s) and long time (2 min.)
ƒ For low viscosity sample, use high rate (100 1/s) and short time (1 min.)
223. TAINSTRUMENTS.COM
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Why modify the yield behavior?
ƒ to avoid sedimentation and increase the shelf live
ƒ to reduce flow under gravity
ƒ to stabilize a fluid against vibration
LHOG6WUHVV
ƒStructured fluids exhibit yield-like behavior, changing from ‘solid-like’ to
readily flowing fluid when a critical stress is exceeded. Rheological
modifiers are often used to control the yield behavior of fluids.
ƒThere are multiple methods to measure Yield stress. The apparent
yield stress measured is not a single value, as it will vary depending
on experimental conditions.
224. TAINSTRUMENTS.COM
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ƒ Stress is ramped linearly from 0 to a value above Yield Stress and the stress at
viscosity maximum can be recorded as Yield Stress
ƒ The measured yield value will depend on the rate at which the stress is increased.
The faster the rate of stress increase, the higher the measured yield value
226. TAINSTRUMENTS.COM
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ƒ Eliminates start-up effects for
more accurate measurements
ƒ Initial high shear rate acts as a
pre-shear, erasing loading effects
ƒ Steady State sensing allows the
sample time to rebuild
ƒ The plateau in shear stress is a
measure of the yield stress.
ƒ At the plateau, Viscosity vs.
Shear Rate will have a slope of -1
slope: -0.995
When the Yield Stress is small, a flow rate sweep from high
to low shear rate is preferred
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0.01000 0.1000 1.000 10.00
osc. stress (Pa)
100.0
1000
G'
(Pa)
Onset point
osc. stress: 1.477 Pa
G': 346.6 Pa
End condition: Finished normally
Sun Block Lotion
Yield stress of a sun block lotion
ƒ Perform strain or stress
sweep in oscillation
ƒ Yield stress is the on set of
G’ curve. It is the critical
stress at which irreversible
plastic deformation occurs.
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ƒ Low shear viscosity 10-3 to 1 s-1
ƒ leveling, sagging, sedimentation
ƒ Medium shear viscosity10-103 s-1
ƒ mixing, pumping and pouring
ƒ High shear viscosity 103 - 106 s-1
ƒ brushing, rolling spraying
9LVFRVLW5DQJHVRI3DLQWVRDWLQJV
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The two coatings show the same consistency after formulation,
but they exhibit very different application performance
0.1 1 10 100 1000 10000 100000
10
-3
10
-2
10
-1
10
0
10
1
10
2
10
3
10
4
HSV
MSV
LSV
Roling
Brushing
Spraying
Mixing
Pumping
Consistency
Appearence
Leveling
Sagging
Sedimentation
At Rest Processing Performance
Viscosity
h
[Pas]
shear rate g [1/s]
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The thixotropy characterizes the time dependence of
reversible structure changes in complex fluids. The
control of thixotropy is important to control:
ƒ process conditions for example to avoid structure build up in pipes
at low pumping rates i.e. rest periods, etc....
ƒ sagging and leveling and the related gloss of paints and coatings,
etc..
Sag Leveling
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In a thixotropic material, there will be a hysterisis between the two curves
The further the up ramp and down ramp curves differ, the larger the area
between the curves, the higher the thixotropy of the material.
See also AAN 016 – Structured Fluids
Stress is ramped up linearly,
and then back down, over the
same duration
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0 20 40 60 80 100 120
10
2
G'o
G'oo
after preshear
Frequency 1Hz
strain 2%
preshear 10s at 60 s
-1
η*
G'
G''
Modulus
G',
G''
[Pa];
Viscosity
η
*
[Pas]
time t min]
Structure build up
Pre-shear the sample
to break down
structure. Then
monitor the increase
of the modulus or
complex viscosity as
function of time.
ܩᇱ ݐ ൌ ܩԢ ሺܩԢஶ െ ܩԢሻሺͳ െ ݁௧Ȁఛ) τ = characteristic recovery time
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ƒThe non-sagging formula (with additive) has both a shorter recovery
time and a higher final recovered viscosity (or storage modulus), and
the recovery parameter takes both of these into account to predict
significantly better sag resistance.
ƒThe ratio η(∞) /t, is the recovery parameter (a true thixotropic index),
and has been found to correlate well to thixotropy-related properties
such as sag resistance and air entrainment.
Rheology in coatings, principles and methods
RR Eley - Encyclopedia of Analytical Chemistry, 2000 - Wiley Online Library
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x
x
x x x x x x
x
x
x
x
Ϭ ϭϬ ϮϬ ϯϬ ϰϬ ϱϬ ϲϬ ϳϬ
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ƒ use small particles to reduce sedimentation speed
ƒ add rheological modifier like clay to stabilize the suspension
and keep the particles in suspension
The temperature
dependence of the
modulus governs the
behavior during the
application to the skin
Sticks: Rheology and process performance
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0.1 1 10 100
10
1
10
2
10
3
0.1 1 10 100
-1.0
-0.5
0.0
0.5
1.0
1.5
2.0
complex viscosity
G'
G''
Modulus
G',
G''
[Pa];
Viscosity
η
*
[Pa
s]
frequency ω [rad/s]
tan δ
tan
δ
ƒ Many dispersion exhibit
solid like behavior at rest
ƒ The frequency
dependence and the
absolute value of tan δ
correlate with long time
stability
Cosmetic lotion
ƒ Note: strain amplitude has to be in the linear region
246. TAINSTRUMENTS.COM
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ƒ Check the online manuals and error help.
ƒ Contact the TA Instruments Hotline
ƒ Phone: 302-427-4070 M-F 8-4:30 EST
ƒ Select Thermal , Rheology or Microcalorimetry Support
ƒ Email: thermalsupport@tainstruments.com or
rheologysupport@tainstruments.com or
microcalorimetersupport@tainstruments.com
ƒ Call your local Technical or Service Representative
ƒ Call TA Instruments
ƒ Phone: 302-427-4000 M-F 8-4:30 EST
ƒ Check out our Website: www.tainstruments.com
ƒ For instructional videos go to: www.youtube.com/user/TATechTips
249. TAINSTRUMENTS.COM
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(E or G)
(E' or G')
(E or G)
(E' or G')
log Frequency Temperature
ƒ Linear viscoelastic properties are both time-dependent and
temperature-dependent
ƒ Some materials show a time dependence that is proportional to the
temperature dependence
ƒ Decreasing temperature has the same effect on viscoelastic
properties as increasing the frequency
ƒ For such materials, changes in temperature can be used to “re-scale”
time, and predict behavior over time scales not easily measured
250. TAINSTRUMENTS.COM
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ƒ TTS can be used to extend the frequency beyond the
instrument’s range
ƒ Creep TTS or Stress Relaxation TTS can predict
behavior over longer times than can be practically
measured
ƒ Can be applied to amorphous, non modified polymers
ƒ Material must be thermo-rheological simple
ƒ One in which all relaxations times shift with the same shift factor aT
251. TAINSTRUMENTS.COM
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ƒ If crystallinity is present, especially if any melting
occurs in the temperature range of interest
ƒ The structure changes with temperature
ƒ Cross linking, decomposition, etc.
ƒ Material is a block copolymer (TTS may work within a limited
temperature range)
ƒ Material is a composite of different polymers
ƒ Viscoelastic mechanisms other than configuration changes of the
polymer backbone
ƒ e.g. side-group motions, especially near the Tg
ƒ Dilute polymer solutions
ƒ Dispersions (wide frequency range)
ƒ Sol-gel transition
252. TAINSTRUMENTS.COM
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ƒ Decide first on the Reference Temperature: T0. What is the
use temperature?
ƒ If you want to obtain information at higher frequencies or
shorter times, you will need to conduct frequency (stress
relaxation or creep) scans at temperatures lower than T0.
ƒ If you want to obtain information at lower frequencies or
longer times, you will need to test at temperatures higher
than T0.
ƒ Good idea to scan material over temperature range at
single frequency to get an idea of modulus-temperature
and transition behavior.
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ƒ Master Curves can be generated using shift factors
derived from the Williams, Landel, Ferry (WLF)
equation
log aT= -c1(T-T0)/c2+(T-T0)
ƒ aT = temperature shift factor
ƒ T0 = reference temperature
ƒ c1 and c2 = constants from curve fitting
ƒ Generally, c1=17.44 c2=51.6 when T0 = Tg
262. TAINSTRUMENTS.COM
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ƒ Sometimes you shouldn’t use the WLF equation (even if it
appears to work)
ƒ If T Tg+100°
C
ƒ If T Tg and polymer is not elastomeric
ƒ If temperature range is small, then c1 c2 cannot be calculated
precisely
ƒ In these cases, the Arrhenius form is usually better
ln aT = (Ea/R)(1/T-1/T0)
ƒ aT = temperature shift factor
ƒ Ea = Apparent activation energy
ƒ T0 = reference temperature
ƒ T = absolute temperature
ƒ R = gas constant
ƒ Ea = activation energy
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ƒ Strain control mode ƒ Stress control mode
ƒ Fast data acquisition is used for monitoring fast changing
reactions such as UV initiated curing
ƒ The sampling rate for this mode is twice the functional oscillation
frequency up to 25Hz.
ƒ The fastest sampling rate is 50 points /sec.
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Control variables:
ƒ Osc torque
ƒ Osc stress
ƒ Displacement
ƒ % strain
ƒ Strain
ƒ Common frequency range: 0.1 – 100 rad/s.
ƒ Low frequency takes long time
ƒ As long as in the LVR, the test frequency can be set either from
high to low, or low to high
ƒ The benefit doing the test from high to low
ƒ Being able to see the initial data points earlier
284. TAINSTRUMENTS.COM
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ƒ It is important to setup normal force control during any temperature
change testing or curing testing
ƒ Some general suggestions for normal force control
ƒ For torsion testing, set normal force in tension: 1-2N ± 0.5-1.0N
ƒ For curing or any parallel plate testing, set normal force in
compression: 0 ± 0.5N