Introduction to Viscometry and Rheology, Basics, Rotational Testing. Basic Seminar Applied Rheology

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1 Introduction to Viscometry and Rheology, Basics, Rotational Testing Basic Seminar Applied Rheology

2 Contents Definition of basic rheological parameters Viscosity and elasticity Deformation, shear stress and shear rate Parameters changing viscosity Temperature, time and pressure Newtonian and Non-Newtonian flow behavior Yield stress Thixotropic and rheopectic flow behavior 2

3 Definition of basic rheological parameters Viscosity and elasticity Viscosity (Dashpot) Elasticity (Spring) Real Systems Rotation and Oscillation Rotation and Oscillation 3

4 Definition of basic rheological parameters Calculation of the dynamic viscosity Viscosity (dynamic) [Pa s] Shear stress [Pa] Deformation [-] Shear rate [1/s] = 4

5 Definition of basic rheological parameters Calculation of the dynamic viscosity y A F y x v = Force Area = F A N m 2 = Pa = Displacement Distance = x y m m = dv dy = d dt m 1 = s m s 5

6 Definitionen of rheologischer basic rheological Größen parameters Calculation of the dynamic viscosity Torque M d Shear factor A Viscosity = = Shear stress Shear rate Rotational speed Shear factor M 6

7 Definitionen of rheologischer basic rheological Größen parameters Experimental determination of the viscosity Absolute Measurement The geometry factors A and M can be calculated for the sensor (Certificate from the manufacture) Relative Measurement The geometry factors A und M can not be calculated for the sensor (eq Brookfield) 7

8 Definition of basic rheological parameters Units of viscosity = Dynamic (shear-)viscosity [Pa s] = / 1 Pa s = 1000 mpa s 1 mpa s = 1cP (centi Poise) = Shear stress [Pa] = Shear rate [1/s] 8

9 Definition of basic rheological parameters Units of viscosity = Kinematic Viscosity [mm 2 /s] = / 1 mm 2 /s = 1 cst (centi Stokes) = Density [kg/m 3 ] rel = Relative Viscosity [-] rel = 1 / 2 eq HAAKE-Unit 9

10 Definition of basic rheological parameters Units of viscosity * = Complex dynamic * = G*/i (oscillatory-) viscosity [Pa s] 1 Pa s = 1000 mpa s 1 mpa s = 1 cp (centi Poise) G* = Complex modulus [Pa] = Angular frequency [rad/s] i = Imaginary Unit (= -1) 10

11 Definition of basic rheological parameters Units of viscosity e = Extensional viscosity [Pa s] e = ( )/ = Rate of deformation [1/s] 11

12 Contents Parameters changing viscosity Temperature, time and pressure 12

13 Einflussgrößen Parameters changing auf die viscosity Viskosität Viscosity is not a constant Chem/physical composition = f ( S ) Temperature = f ( T ) Pressure = f ( p ) Shear rate = f ( ) Time Miscelaneous = f ( t ) Shear time, relaxation time eg electric, magnetic fiel intensity Viscosity should always be indicated togehter with the relevant influencing parameters eq: = 1,4 Pa s (20 C, 100 s -1, after 1 min pre-shear 200 s -1 ) 13

14 [mpa s] Parameters changing viscosity Temperature dependence of a mineral oil At 20 C: ( / )/ T = /K T [ C] 30 14

15 Parameters changing viscosity Viscosity of fluids measured at 20 C Fluid Viscosity [mpa s] Water Fruit juice, wine Saccharose-solution Coffee cream Olive oil Honey Bitumen (40 g in 100 ml Wasser)

16 [Pas] Parameters changing viscosity Pressure depence of viscosity of cruede oil 10 Increase of the viscosity of 20 % with a pressure increase of 15 bar Viscosity curve at 15 bar Viscosity curve at atmosheric pressure [1/s] 16

17 Contents Newtonian and non-newtonian flow behavior 17

18 log viscosity log shear stress Parameters changing viscosity Shear rate Newtonian flow behavior The viscosity is not a function of the applied shear rate f( Water Mineral oil Slope of 1 Bitumen log shear rate 18

19 log viscosity log shear stress Parameters changing viscosity Shear rate Viscosity curve: = f ( ) Shear thinning behavior Aka pseudoplastic flow behavior Almost every polymer containing fluid (melts and solutions) Shower gel Skin cream Mayonnaise Slope of 1 Slope > -082 log shear rate 19

20 Newtonsches Newtonian and und Non-Newtonian nicht-newtonsches flow behavior Fließverhalten Shear thinning flow behavior Rest state Ridgid rods Random coils Droplets Particles Sheared Orientation Extension Deformation Dis-aggregation Liquid crystal Polymeric fluids Emulsions Suspensions 20

21 viscosity [Pa s] Newtonian and Non-Newtonian flow behavior Shear rates for different paint applications Storage, shelf live Transport Producing paint Applying paint Levelling Sedimentation Consistency in the can Brushing, spraying, rolling shear rates [1/s] 21

22 Newtonian and Non-Newtonian flow behavior Applications and typical shear rates Application Shear rate [s -1 ] Sedimentation Phase separation Levelling, running Extrusion Dip coating Chewing Pumping, stirring Brushing Spraying

23 log viscosity log shear stress Newtonian and Non-Newtonian flow behavior Dilatant flow behavior PVC-plastisol Clay dispersions Quicksand log shear rate 23

24 Contents Yield stress 24

25 Yield stress Microscopic picture The yield stress 0 is the shear stress required, to overcome elastic behavior and obtain stationary flow behavior Shear stress 25

26 log viscosity log shear stress Yield stress Bingham flow behavior Mortar 0 Extrapolation of the flow curve shear rate 26

27 log viscosity log shear stress Yield stress Plastic flow behavior Chocolate Tooth paste Printing ink 0 Extrapolation of the flow curve shear rate [1/s] 27

28 Flow behavior Mathematic models Newton = Bingham = 0 + Shear thinning = K n (n < 1) Ostwald de Waele Plastic = 0 + K n Herschel-Bulkley, Casson Dilatant = K n (n > 1) 28

29 log shear stress log viscosity Fließverhalten Flow behavior Overview log shear rate log shear rate Newtonian Shear thinning Dilatant Plastic Bingham 29

30 Contents Thixotropic and rheopectic flow behavior 30

31 Thixotropic Scherzeitabhängiges and rheopectic Fließverhalten flow behavior Thixotropy Decrease of viscosity as a function of time under shear 100% recovery as a function of time without shearing Primary-Particles Agglomerates Agglomerates Network-structure 31

Thixotropic Scherzeitabhängiges and rheopectic Fließverhalten flow behavior Determination Time curve Recording of initial state (low shear stress, shear rate or oscillation) Disaggregation at

32 Thixotropic Scherzeitabhängiges and rheopectic Fließverhalten flow behavior Determination Time curve Recording of initial state (low shear stress, shear rate or oscillation) Disaggregation at constant shear rate (eg 100 1/s) until a constant is reached Re-aggregation (low shear stress, shear rate or oscillation) level Thixotropic-Loop Ramp up, (peak hold) and ramp down Hysteresis area as a measure for thixotropy 32

33 log viscosity Thixotropic Scherzeitabhängiges and rheopectic Fließverhalten flow behavior Time curve and structure recovery Rotation (Oscillation) 0 Rotation >> 0 Rotation (Oscillation) 0 Range 1 Initial State Range 2 Disaggregation Range 3 Reaggregation t 1 t 2 time t 33

34 shear stress viscosity Thixotropic Scherzeitabhängiges and rheopectic Fließverhalten flow behavior Thixotropic loop fresh building material peak hold shear rate [1/s] 34

35 shear stress viscosity Thixotropic Scherzeitabhängiges and rheopectic Fließverhalten flow behavior Rheopexy Real Rheopexy is not observed often double check whether an artifact is observed Dispersions with high concentration of solids (eg Latex) shear rate [1/s] 35

36 Flow behavior Conclusions Newtonian flow behavior: f ( ) Non-Newtonian Flow behavior: = f ( ) Bingham (yield stress) Shear thinning (pseudoplastic) Plastic (yield stress) Dilatant (shear thickening) Time dependant flow behavior: = f (t, ) Thixotropy Rheopexy 36

37 Thank you for your attention! Any Questions? 37

Contents. Preface XIII. 1 General Introduction 1 References 6

Contents. Preface XIII. 1 General Introduction 1 References 6 VII Contents Preface XIII 1 General Introduction 1 References 6 2 Interparticle Interactions and Their Combination 7 2.1 Hard-Sphere Interaction 7 2.2 Soft or Electrostatic Interaction 7 2.3 Steric Interaction