CHEM 550 – Formulation of Modern Coatings Spring 2006 Polymers and Coatings Program California Polytechnic State University 1 ppt00 1 1 Coating Rheology Coating Rheology - Outline Outline z Rheological Properties of Coatings Rheological Properties of Coatings – Viscosity, Shear Viscosity, Shear-thinning, thinning, Thixotropy Thixotropy, , Viscoelasticity Viscoelasticity, , Surface & Interfacial Tension, etc. Surface & Interfacial Tension, etc. z Impact of Rheology on Coating Process Impact of Rheology on Coating Process – Paint Mixing, Application, Sag & Leveling, etc. Paint Mixing, Application, Sag & Leveling, etc. z Effect of Coating Formulation Aspects on Effect of Coating Formulation Aspects on Rheology Rheology – Solids Level, Binders, Pigments, Additives, Solids Level, Binders, Pigments, Additives, Interactions Interactions ppt00 2 2 Rheological Properties of Coatings Rheological Properties of Coatings z Rheology & Viscosity Definitions z Effect of Shear Rate on Viscosity z Newtonian Vs Non-Newtonian Behavior z Shear-Thinning, Pseudoplasticity, Thixotropy, etc. z Shear Vs Extensional Viscosity z Viscoelasticity z Measurement of Rheological Properties
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CHEM 550 – Formulation of Modern Coatings Spring 2006
Polymers and Coatings ProgramCalifornia Polytechnic State University 1
Rheological Properties of CoatingsRheological Properties of Coatings–– Viscosity, ShearViscosity, Shear--thinning, thinning, ThixotropyThixotropy, , ViscoelasticityViscoelasticity, ,
Surface & Interfacial Tension, etc.Surface & Interfacial Tension, etc.
Impact of Rheology on Coating ProcessImpact of Rheology on Coating Process–– Paint Mixing, Application, Sag & Leveling, etc.Paint Mixing, Application, Sag & Leveling, etc.
Effect of Coating Formulation Aspects on Effect of Coating Formulation Aspects on RheologyRheology–– Solids Level, Binders, Pigments, Additives, Solids Level, Binders, Pigments, Additives,
InteractionsInteractions
ppt00 2 2
Rheological Properties of CoatingsRheological Properties of Coatings
Rheology & Viscosity Definitions
Effect of Shear Rate on Viscosity
Newtonian Vs Non-Newtonian Behavior
Shear-Thinning, Pseudoplasticity, Thixotropy, etc.
Shear Vs Extensional Viscosity
Viscoelasticity
Measurement of Rheological Properties
CHEM 550 – Formulation of Modern Coatings Spring 2006
Polymers and Coatings ProgramCalifornia Polytechnic State University 2
ppt00 3 3
Coating Process OverviewCoating Process Overview
Raw Materials
Mixing / Blending
Storage (Shelf / Pot)
Delivery to Applicator
Application
Flow & Leveling
Drying / Curing
What are the Requirementsin Each Step?
ppt00 4 4
RheologyRheology
Science concerned with the Science concerned with the flow and deformation of flow and deformation of
materialsmaterials
CHEM 550 – Formulation of Modern Coatings Spring 2006
Polymers and Coatings ProgramCalifornia Polytechnic State University 3
ppt00 5 5
Which is more viscous?Which is more viscous?
Water or cooking oil?
Cooking oil or honey?
Honey or mayonnaise?
ppt00 6 6
Viscosities of Common MaterialsViscosities of Common Materials
100 centipoise (cps) = 1 poise 10 poise = 1 Pa s
1 cps = 1 mPa s
5000Honey
1000Glycerine
100Olive Oil
1Water
Viscosity (cps)
CHEM 550 – Formulation of Modern Coatings Spring 2006
Polymers and Coatings ProgramCalifornia Polytechnic State University 4
ppt00 7 7
ViscosityViscosity
Viscosity is resistance of a material to flow
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ViscosityViscosity
Velocity = 0
Velocity = V
ViscosityViscosityMeasure of the resistance of a fluid to an Measure of the resistance of a fluid to an
imposed flowimposed flow
CHEM 550 – Formulation of Modern Coatings Spring 2006
Polymers and Coatings ProgramCalifornia Polytechnic State University 5
If Viscosity is Independent of Shear If Viscosity is Independent of Shear Rate Coating is NewtonianRate Coating is Newtonian
Shea
r Stre
ss, P
a
Visc
osity
, Pa s
Shear Rate, s-1 Shear Rate, s-1
Stress Rate
Viscosity
γητ &=
CHEM 550 – Formulation of Modern Coatings Spring 2006
Polymers and Coatings ProgramCalifornia Polytechnic State University 6
ppt00 11 11
Bubble ViscometersBubble ViscometersSimilar in Concept to Falling Ball. However, Bubble is Deformable -Theoretical Analysis is Difficult.– e.g. Gardner Bubble Viscometer
(ASTM D1545)
Falling Body Type has Very Limited Control Over Measurement Parameters (Shear Rates, Shear Stress)