1、MORE SOLUTIONS TO STICKY PROBLEMS Page i Brookfield Engineering Labs., Inc. MORE SOLUTIONS TO STICKY PROBLEMS: TABLE OF CONTENTS INTRODUCTION 1 CHAPTER 1: Brookfield School of Thought 2 1.1 Why Make Rheological Measurements? .2 1.2 Thinking Rheo-Logically .2 1.3 Three Schools of Thought on Viscosity
2、 Measurement .21.3.1 The Pragmatic School 21.3.2 The Theoretical School 21.3.3 The Academic School 3 CHAPTER 2: Equipment Systems for Applications 3 2.1 Equipment for Specific Situations 3 2.2 Viscometers .3 2.3 Rheometers .4 2.4 Spindle Geometries .42.4.1 Disc Spindles 42.4.2 Cylindrical Spindles 4
3、2.4.3 Coaxial Cylinders 42.4.4 Cone/Plate Geometry .42.4.5 T-Bar Spindles 52.4.6 Vane Spindles .5 2.5 Temperature Control 52.5.1 Temperature Baths .52.5.2 Thermosel System 52.5.3 Peltier (Thermo-electric Systems) 5 2.6 Small Sample Volume .52.6.1 Small Sample Adapter 52.6.2 UL Adapter 52.6.3 DIN Ada
4、pter 52.6.4 Thermosel System 52.6.5 Cone/Plate Systems .6 2.7 Low Viscosity .62.7.1 UL Adapter 62.7.2 Small Sample Adapter 62.7.3 Thermosel System 62.7.4 Wells-Brookfield Cone/Plate Viscometer 6 2.8 High Temperature.62.8.1 Thermosel System 62.8.2 Temperature Baths .62.8.3 Cone/Plate with Embedded He
5、ating 6 2.9 Defined Shear Rate .6 2.10 High Shear Rate .72.10.1 Wells-Brookfield Cone/Plate Viscometer/Rheometer 72.10.2 CAP Viscometer/Rheometer 72.10.3 RST Rheometer 72.10.4 PVS Rheometer 7 2.11 Defined Shear Stress .7 2.12 Non-Flowing Sample Materials 82.12.1 Helipath Stand 82.12.2 Spiral Adapter
6、 .82.12.3 Vane Spindles .8 2.13 Special Accessory Items 82.13.1 Quick Connect 82.13.2 Spindle Extensions .8 2.14 Fumes and Hazardous Locations 82.14.1 Purge Fittings .82.14.2 Explosion-Proof Construction 9 2.15 Software .9 2.16 Process Control .9CHAPTER 3: Making Measurements 9 3.1 Why You Should Re
7、ad This Chapter .9 3.2 How the Brookfield Viscometer Works .9 3.3 Spring Torque .10 3.4 Viscosity Measurement Techniques .103.4.1 Record Keeping 103.4.2 The Spindle and the Guardleg 103.4.3 Selecting a Spindle Speed .103.4.4 Sample Container Size .113.4.5 Sample Conditions .113.4.6 Spindle Immersion
8、 113.4.7 Sensitivity and Accuracy .113.4.8 Obtaining a Viscometer Reading 123.4.9 A Calibration Check .123.4.10 Recalibrating the Brookfield Viscometer 13 3.5 Viscometer Maintenance14 3.6 Viscometer Troubleshooting .14 3.7 Other Viscosity Measurement Methods .15 CHAPTER 4: Rheology Basics 15 4.1 Com
9、ing to Grips with Rheology .15 4.2 Viscosity .15 4.3 Newtonian Fluids 15 4.4 Non-Newtonian Fluids .16 4.5 Thixotropy and Rheopexy 17 4.6 Laminar and Turbulent Flow 17 4.7 Yield Behavior 18 4.8 What Affects the Rheological Property? 184.8.1 Temperature .194.8.2 Shear Rate .194.8.3 Measuring Condition
10、s .194.8.4 Time 204.8.5 Pressure .204.8.6 Previous History .204.8.7 Composition and Additives .204.8.8 Special Characteristics of Dispersions and Emulsions 20MORE SOLUTIONS TO STICKY PROBLEMS Page ii Brookfield Engineering Labs., Inc. CHAPTER 5: Data Analysis .21 5.1 Advanced Methods for Rheological
11、 Analysis 21 5.2 Defining Operating Parameters of Various Spindle Geometries .215.2.1 Cylindrical Spindles 215.2.2 Coaxial Cylinders 225.2.3 Cone and Plate .225.2.4 Disc and T-Bar Spindles .225.2.5 Spiral Adapter Spindle 235.2.6 “Paddle” / “Paste” Spindles .235.2.7 Vane Spindles .235.2.8 Other Speci
12、al Spindles .23 5.3 Analyzing Time-Independent Non-Newtonian Fluids .235.3.1 Ratio Methods 235.3.2 Graphic Methods 235.3.3 Template Method 245.3.4 Dynamic Yield Value Determination .24 5.4 Static Yield Value Determination 25 5.5 Analyzing Time-Dependent, Non-Newtonian Fluids .25 5.6 Temperature Depe
13、ndence of Viscosity 25 5.7 Math Models 26 5.8 Brookfield Application Software .26 5.9 Miscellaneous Methods .27 CHAPTER 6: Test Methods 27 6.1 Single Point Viscosity Test .27 6.2 Controlled Rate Ramp .27 6.3 Up-Down Rate Ramp .27 6.4 Time Sensitivity Test.27 6.5 Temperature Sensitivity Test 28 6.6 T
14、emperature Profiling with Up-Down Rate .28 6.7 Static Yield Test 28 6.8 Dynamic Yield Test .28 6.9 Recovery 28 6.10 Tests Unique to RST Rheometer .29 APPENDIX A: Specifications, Ranges, and Operating Parameters .30 A.1 Dial-Reading Viscometer Spindles and Speeds .31 A.2 Digital Viscometers/Rheometer
15、s Spindles and Speeds .32 A.3 Disc Spindle Information for Standard Viscometers/Rheometers 32 A.4 Cylindrical Spindles for Dial-Reading Viscometer and Digital Viscometers/ Rheometers .33 A.5 Wells-Brookfield Cone/Plate Viscometers/Rheometers 35 A.6 Small Sample Adapter .36 A.7 UL Adapter .38 A.8 The
16、rmosel System 39 A.9 DIN Adapter 40 A.10 Helipath Stand with T-Bar Spindles .41 A.11 Spiral Adapter 42 A.12 Vane Spindles 43 A.13 KU-2 (Krebs) Viscometer .44 A.14 YR-1 Yield Stress Rheometer 45 A.15 CAP 1000+ and CAP 2000+ Viscometers 46 A.16 Falling Ball Viscometer 47 A.17 RST Rheometer S by sugges
17、ting ways in which specific pieces of hardware may be used to solve viscosity mea- surement problems;S by explaining the basic principles of rheology and their relation to measurements made with Brook- field equipment;S by discussing factors that affect rheological be- havior and how these may be co
18、ntrolled;S by outlining advanced mathematical procedures for detailed analysis of viscosity data;S by consolidating a variety of useful range tables, formulas, and specifications for many Brookfield Viscometers and accessories.We hope that you will find this book useful and refer to it often. It is
19、our attempt to answer all at once many of the questions we have been asked over the years. If you have any questions that are not answered here, or if you want to suggest improvements or changes for future editions, please feel free to contact us. It was, after all, the input of people like yourself
20、 that made this book possible in the first place.For additional information, applications, etc., please visit our website at . INTRODUCTIONMORE SOLUTIONS TO STICKY PROBLEMS Page 2 Brookfield Engineering Labs., Inc. 1.1 Why Make Rheological Measurements?Anyone beginning the process of learning to thi
21、nk Rheo-Logically must first ask the question, “Why should I make a viscosity measurement?”. The answer lies in the experiences of thousands of people who have made such measurements, showing that much useful behavioral and predictive information for various products can be obtained, as well as know
22、ledge of the effects of processing, formulation changes, aging phenomena, etc.A frequent reason for the measurement of rheological properties can be found in the area of quality control, where raw materials must be consistent from batch to batch. For this purpose, flow behavior is an indirect measur
23、e of product consistency and quality.Another reason for making flow behavior studies is that a direct assessment of processability can be obtained. For example, a high viscosity liquid requires more power to pump than a low viscosity one. Knowing rheological behavior, therefore, is useful when desig
24、n- ing pumping and piping systems.It has been suggested that rheology is the most sensitive method for material characterization because flow behavior is responsive to properties such as mo- lecular weight and molecular weight distribution. This relationship is useful in polymer synthesis, for examp
25、le, because it allows relative differences to be seen without making molecular weight measurements. Rheological measurements are also useful in following the course of a chemical reaction. Such measurements can be employed as a quality check during production or to monitor and/or control a process.
26、Rheological mea- surements allow the study of chemical, mechanical, and thermal treatments, the effects of additives, or the course of a curing reaction. They are also a way to predict and control a host of product properties, end use performance and material behavior. 1.2 Thinking Rheo-LogicallyTo
27、begin, consider the question, “Can some rheo- logical parameter be employed to correlate with an aspect of the product or process?” To determine this, an instinct must be developed for the kinds of chemical and physical phenomena which affect the rheological response. For the moment, assume this inf
28、ormation is known and several possibilities have been identified. The next step is to gather preliminary rheological data to determine what type of flow behavior is characteristic of the system under consideration. At the most basic level, this involves making measurements with which- ever Brookfiel
29、d Viscometer is available and drawing some conclusions based on the descriptions of flow behavior types in Chapter 4.Once the type of flow behavior has been identified, more can be understood about the way components of the system interact (more information on what affects the rheological property c
30、an be found in Section 4.8). The data thus obtained may then be fitted to one of the mathematical models which have been success- fully used with Brookfield instruments. Many of these models may be found in Chapter 5.Such mathematical models range from the very simple to the very complex. Some of th
31、em merely involve the plotting of data on graph paper; others re- quire calculating the ratio of two numbers. Some are quite sophisticated and require use of programmable calculators or computers. This kind of analysis is the best way for getting the most from our data and often results in one of tw
32、o “constants” which summarize the data and can be related to product or process perfor- mance.Once a correlation has been developed between rheological data and product behavior, the procedure can then be reversed and rheological data may be used to predict performance and behavior. 1.3 Three School
33、s of Thought on Viscosity Mea- surementIn our experience there are basically three schools of thought on the use of viscometers in applications rheology. We present them here and invite you to decide which you fall into, remembering that there is no “right” one and that each has its merits.1.3.1 The
34、 Pragmatic SchoolThe first school of thought is the most pragmatic. The person who adheres to this school cares only that the Brookfield Viscometer generates numbers that tell something useful about a product or process. This person has little or no concern about rheologi- cal theory and measurement
35、 parameters expressed in absolute terms. Quality control and plant produc- tion applications are typical of this category.1.3.2 The “Theoretical” School The second school of thought involves a more theoretical approach. Those adhering to this school know that some types of Brookfield Viscometers wil
36、l not directly yield defined shear rates and absolute viscosities for non-Newtonian fluids. However, these people often find that they can develop cor- relations of “dial viscosity” with important product or process parameters. Many people follow this school of thought. The applications rheology lit
37、erature is replete with statements along the line of “I know the data isnt academically defined, but I keep this fact in mind and treat the multi-point rheology information as if it were.” In many cases, this produces eminently satisfying results and eliminates the necessity of buying a highly sophi
38、sticated and very expensive piece of rheological equipment. CHAPTER 1: Brookfield School of ThoughtMORE SOLUTIONS TO STICKY PROBLEMS Page 3 Brookfield Engineering Labs., Inc.1.3.3 The Academic School The third school of thought is quite academic in nature. People adhering to this school require that
39、 all measurement parameters, particularly shear rate and shear stress, be defined and known. They need equipment with defined geometries such as cone/plate or coaxial cylinders. Examples from the Brookfield line would be the Wells-Brookfield Cone/ Plate, CAP Viscometers, BF35 Viscometers, RST and PV
40、S Rheometers and Standard Viscometers and Rheometers with the following geometries: the UL adapter, Small Sample Adapter, Thermosel, Din Adapter and Spiral Adapter accessories, as well as the RST and PVS Rheometers. With this equipment the shear rate is defined and accurate absolute vis- cosities ar
41、e obtained directly from the measurement.That, then, is our view of the three schools of thought on viscosity measurement. You may need to think in terms of any or all of these depending on your background, approach, goals, and type of equip- ment available. Brookfield Viscometer users fall into all
42、 three; the following chapters present information of use to each. 2.1 Equipment for Specific SituationsThe purpose of this chapter is to provide an overview of Brookfields entire line of Viscometers, Rheometers and related accessories, and to suggest ways in which these products may be helpful in s
43、olving specific vis- cosity measurement problems. This information will be useful to people adhering to all three schools of thought on viscosity measurement.The equipment has been organized into functional groups to help you quickly find the items of most inter- est to you:ViscometersRheometersSpin
44、dle GeometriesTemperature ControlSmall Sample Volume Low ViscosityHigh TemperatureDefined Shear RateHigh Shear RateDefined Shear StressNon-Flowing Sample MaterialsSpecial Accessory ItemsFumes and Hazardous LocationsProcess Control 2.2 ViscometersBrookfield laboratory Viscometers are available in thr
45、ee basic types: dial-reading (analog), digital, and programmable. The most significant difference be- tween them is the manner in which the viscosity reading is displayed. The dial-reading type is read by noting the position of a pointer in relation to a rotating dial; the Digital type is read by me
46、ans of an LCD or graphical display. In addition, the Digital Viscometer includes a serial or USB output that can be used in conjunction with Brookfield Software for data storage, data analysis and instrument control. Programmable viscometers utilize a touch screen interface and provide enhanced func
47、tionality.In most respects dial-reading and Digital Viscometers are functionally similar. The operating procedures for both are essentially the same, they are available in the same model variations, they accept the same Brookfield accessories, and are generally interchange- able (model for model) in
48、 most viscosity specifications requiring Brookfield Viscometers.The dial-reading type is the least expensive Brook- field Viscometer and is suitable for most applications where samples are to be tested over a short period of time and a permanent detailed record of rheological behavior is not require
49、d. This is due to the fact that while the Viscometer rotates continuously, readings may be made only intermittently, when the pointer passes under the vision glass, or when the reading is held and the Viscometer stopped. Long term viscosity tests necessitate frequent operator attention, and some fast-acting processes dictate continuous monitoring.The Digital Viscometer, with its continuous sensing and display, is more suited to such situations. It may be left unattended for long periods, and the data output may be adjusted to provide a detailed re
