An Introduction to Rheology : Phenomenon, Concept, Measuring, and Case Study

1. TA 成大講稿 4/16/2013 An Introduction to Rheology: Phenomenon, Concept, Measuring, and Case Study Complex Fluids & Molecular Rheology Lab., Department of Chemical Engineering

3. The XVIth International Congress on Rheology • Colloids and Suspensions • Emulsions and Foams • Solids and Granular Materials • Industrial Rheology • Complex Flows • General Rheology • Non-Newtonian Fluid Mechanics • Advanced Experimental Methods • Materials Processing • Polymer Solutions, Melts and Blends • Biopolymers, Biofluids and Foods • Constitutive and Computational Modeling • Rheology of Bio-Pharmaceutical Systems • Rheology of Nano- and Natural Composites • Interfacial Rheology, Micro-rheology & Microfluidics • Associative Polymers, Surfactants and Liquid Crystals • Professor Ken Walters Commemorative Symposium

4. Frequent Q & A • Q: Rheometer = Rheology? A:Unfortunately, the answer is, to a large extent, negative! • Q: How to judge the correctness of rheological data and know the physical meanings? A: Mostly, it’s all about the theories • Q: A practical processing issue can be well characterized by a set of rheological parameters? A: Well,…………………………………………..let’s see!

5. ● Deformable Small molecule Macromolecule • Rheology is the science of fluids or—more precisely—deformablematerials Newton’s law of viscosity 牛頓流體 - 水、有機小分子溶劑等 非牛頓流體 - 高分子溶液、膠體等 黏度η為定值 黏度不為定值 (尤其在快速流場下)

6. 非牛頓流體的三大特徵 • 特徵時間與無因次群分析

7. 非 牛 頓 流 體 的 特 徵 • 非牛頓黏度(Non-Newtonian Viscosity) - Shear Thinning Flow curve for non-Newtonian Fluids 牛頓流體 (甘油加水) 非牛頓流體 (高分子溶液)

8. 正向力差的效應(Normal Stress Differences) - Rod-Climbing 牛頓流體 (水) 非牛頓流體 (稀薄高分子溶液)

9. 記憶效應(Memory effects) -Elastic Recoil - Open Syphon Flow

10. Time-dependent effects (搖變性) Thixotropy behavior Anti-thixotropy behavior A decrease (thixotropy) and increase (anti-thixotropy) of the apparent viscosity with time at a constant rate of shear, followed by a gradual recovery when the motion is stopped • The distinction between a thixotropic fluid and a shear thinning fluid: • A thixotropic fluid displays a decrease in viscosity over time at a constant • shear rate. • A shear thinning fluid displays decreasing viscosity with increasing shear • rate.

11. 非 牛 頓 流 體 的 不 穏 定 性: 黏 彈 性 效 應 “The mountains flowed before the Lord” [From Deborah’s Song, Biblical Book of Judges, verse 5:5], quoted by Markus Reiner at the Fourth International Congress on Rheology in 1963 • 收縮流道 - 描述非牛頓流體行為之程度 流體的特徵或 “鬆弛”時間 流動系統的特徵時間 剪切速率 牛頓流體 (葡萄糖漿) 非牛頓流體 (0.057%聚丙烯醯胺/葡萄糖 溶液)

12. Lubrication High-speed coating Rolling Spraying • 典型製程之流場強度範圍 Injection molding Pipe flow Chewing Extrusion Sedimentation Typical viscosity curve of a polyolefin- PP homopolymer, melt flow rate (230 C/2.16 Kg) of 8 g/10 min- at 230 C with indication of the shear rate regions of different conversion techniques. [Reproduced from M. Gahleitner, “Melt rheology of polyolefins”, Prog. Polym. Sci., 26, 895 (2001).]

13. Melt instability Sharkskin Melt fracture Photographs of LLDPE melt pass through a capillary tube under various shear rates. The shear rates are 37, 112, 750 and 2250 s-1, respectively. [Reproduced from R. H. Moynihan, “The Flow at Polymer and Metal Interfaces”, Ph.D. Thesis, Department of Chemical Engineering, Virginia Tech., Blackburg, VA, 1990.] [Retrieved from the video of Non-Newtonian Fluid Mechanics (University of Wales Institute of Non-Newtonian Fluid Mechanics, 2000)]

14. Instability for dilute solutions Taylor vortex R2 R1 Flow visualization of the elastic Taylor-Couette instability in Boger fluids. [http://www.cchem.berkeley.edu/sjmgrp/] [S. J. Muller, E. S. G. Shaqfeh and R. G. Larson, “Experimental studies of the onset of oscillatory instability in viscoelastic Taylor-Couette flow”, J. Non-Newtonian Fluid Mech., 46, 315 (1993).]

15. 剪切流與非剪切流 • 基礎流變量測模式與功能

16. Two standard typesof flows, shear and shearfree, are frequently used to characterize polymeric liquids 典 型 均 勻 流 場 (b) Shearfree (a) Shear Elongation rate Steady simple shear flow Shear rate Streamlines for elongational flow (b=0)

17. The Stress Tensor y x z Elongational Flow Shear Flow Total stress tensor* Stress tensor Hydrostatic pressure forces

18. 流變夾具種類與適用範圍 (a) Shear Concentrated Regime Dilute Regime Homogeneous deformation:* Cone-and-Plate Concentric Cylinder Nonhomogeneous deformation: Parallel Plates Capillary (b) Elongation Moving clamps For Melts & High-Viscosity Solutions *Stress and strain are independent of position throughout the sample

19. 基礎流變量測之物理解析與應用

20. Newtonian Power law Zero-shear viscosity, 0 According to the Reptation Theory:

21. Relative Viscosity: Master curves for the viscosity and first normal stress difference coefficient as functions of shear rate for the low-density polyethylene melt shown in previous figure Intrinsic Viscosity: Intrinsic viscosity of dilute polystyrene Solutions, With various solvents, as a function of reduced shear rate β

22. 小振幅反覆式剪切流: 黏性與彈性檢定 Exp b: Small-Amplitude Oscillatory Shear Flow Oscillatory shear strain, shear rate, shear stress, and first normal stress difference in small-amplitude oscillatory shear flow

23. It is customary to rewrite the above equations to display the in-phase and out-of-phase parts of the shear stress Storage modulus Loss modulus Storage and loss moduli, G’ and G”, as functions of frequency ω at a reference temperature of T0=423 K for the low-density polyethylene melt shown in Fig. 3.3-1. The solid curves are calculated from the generalized Maxwell model, Eqs. 5.2-13 through 15

24. Molecular Architecture—The Fingerprints Linear PolymerStar PolymerPom-Pom Polymer polybutadienePolyisoprenePolyisoprene S. C. Shie, C. T. Wu, C. C. Hua, Macromolecules36, 2141-2148 (2003) C. C. Hua, H. Y. Kuo, J Polym Sci Part B: Polym Phys38, 248-261 (2000)

25. 拉 伸 流 黏 度 量 測 與 特 徵 Shearfree Flow Material Functions

26. H. Munstedt, J. Rheol. 24, 847-867 (1980) Hua and Yang, J Polym Res 9, 79-90 (2002)

27. The Rheology of Colloidal Dispersions

28. Onset of shear thickening : the Péclet number • Fluid drag on the particle leads to the Stokes-Einstein relationship: • The mean square of the particle’s displacement is Accordingly, the diffusivity sets the characteristic time scale for the particle’s Brownian motion. • A dimensionless number known as Péclet number, Pe

29. Lubrication hydrodynamics and hydroclusters Pe~1 Pe<<1 Pe>>1 • At (Pe<<1) regime, random collisions among particles make them naturally resistant to flow. • As the shear rate increase (Pe~1), particles become organized in the flow, which lowers their viscosity. • At (Pe>>1) regime, the strong hydrodynamic • coupling between particles leads to the formation of hydroclusters (red particles) which cause an increase in viscosity. • The flow-induced density • fluctuations are known as • hydroclusters which lead to an • increase in viscosity. • The formation of hydroclusters • is reversible, so reducing the • shear rate returns the • suspensions to a stable fluid

30. Controlling shear thickening fluids: to modify colloidal surface • The addition of a polymer “brush” grafted or absorbed onto the particles’ • surface can prevent particles from getting close together. • The figure shows that shear thickening is suppressed by imposing a purely • repulsive force field. • With the right selection of grafted density, molecular weight, and solvent , the • onset of shear thickening moves out of the desired processing regime

31. Case Study I: 導電金屬漿流變性質的鑑定 • Steady-state Viscosity • First normal stress difference • Linear viscoelasticity

32. The Viscosity Curves of Steady Shear Flow A B C D

33. The 1st Normal Stress Curves of Steady Shear Flow A B C D

34. G’ & G’’ A B C D

35. Screen Printing Technique Starting position for a screen printer squeegee gauze medium frame gap (‘snap-off’) emulsion mask board holder board • The screen is fixed just above the board, and the medium lies in front of the flexible squeegee. • The mesh of the screen is pushed down into contact with the board by the squeegee as it moves across the screen, rolling the medium in front of it. The screen printing process medium medium drawn from open mesh snap-off • The squeegee blade first presses the medium into the open apertures of the image, and then removes the excess as it passes across each aperture. • The screen then peels away from the printed surface behind the squeegee, leaving the medium that was previously in the mesh aperture deposited on the board beneath http://www.ami.ac.uk/courses/topics/0222_print/index.html#1

36. Silver paste CM-A Silver paste CM-B Binders sample Powders sample

37. Silver paste Powders sample Binders sample

38. 流變-光學 (Rheo-Optical) 整合量測系統: 結構 vs. 應力

39. Versatile Optical Rheometry Lens PEM Polarier Objective lens Iris Iris Laser Pinhole Flow-LS(large-angle detection) Spatial filter & Beam expander Couette cell Rheology CCD Analyzer Rheo-SALS Lens Screen with aperture (from PEM) 1f 2f Photodiode Lock-in amplifiers Rheo-Birefringence

40. CASE STUDY II : Combined Rheo-Optical Measurements • Rheo-Optical Studies of Shear-Induced Structures in Semidilute Polystyrene Solutions [Kume et al. (1997)] • Shear-induced structure formation in semidilute solutions of high molecular • weight polystyrene was investigated using a wide range of rheo-optical techniques • 2. The effects of shear on the semidilute polymer solutions could be classified into • some regimes w.r.t. shear rate FIG.A complete picture of the shear-induced phase separation and structure formation from a wide range of techniques on the same polymer solutions

41. Continued Comparisons with Mechanical Characterizations: Mechanical Notice that the behavior of the shear viscosity is also classified into three regimes

42. Physics governing the fluid behavior

43. Tips and Recommendations of problem solving Identify an analogous model system that had been studied earlier Go through literature survey and read carefully and apprehensively Design tactics for collecting preliminary data—experimental or computational Discuss with your supervisor or counselor for the significance of the current data and appropriate next steps. Repeat this procedure until the problem has been resolved to a satisfactory extent.

44. People used to tell me, “The problems encountered in industry are typically too complex to be studied in a (academic) lab (like yours)”

45. My response was, “Just because the problems are so complex that they must eventually be resolved in a (academic) lab (like mine)!”

46. TA 成大講稿 4/16/2013 An Introduction to Rheology: Phenomenon, Concept, Measuring, and Case Study Complex Fluids & Molecular Rheology Lab., Department of Chemical Engineering