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Polymeric Coatings Overview

CHEM 550, Spring 2006Ray Fernando, Cal Poly - SLO

Polymeric Coatings Overview

Coating Process – Life CyclePVC, CPVC, NVVChemistry, Function of IngredientsCoating Types – Waterborne, Solvent-Based, High-Solids

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COATINGS ARE USED FORCOATINGS ARE USED FOR……Aesthetics

Decoration, Camouflage, MarkingsTexture

Substrate ProtectionCorrosion Resistance, Wear, Impact

Specialty FunctionsOptical, Electromagnetic, Insulation (Electrical, Thermal), Absorption (Sound), Conductive

CoatingsScience

Polymer Science

Color & Appearance

Rheology

EnvironmentalScience

Colloid & InterfacialScience

Mechanics

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Coating Formulation IngredientsCoating Formulation IngredientsBinders

WaterborneSolvent based

PigmentsHidingColor

FillersAdditives

B

B

BB

BC

C

C

C

C

A A

A

A

A

A A

ABinder

Vehicle

Pigment/Filler

Wet Coating Wet Coating FormulaionFormulaion

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Dry Coating FilmDry Coating Film

Binder

Dry Film – Clear Coat

Pigment/Filler

Binder

Dry Film – Pigmented Coat

Example I: MidExample I: Mid--Quality Interior Wall Quality Interior Wall PaintPaint

Shelf life > 1 year, heat age and freeze-thaw stableSelling price, < $20/galApplication by home owner Do-It-Yourself (DIY)

Brush and roller

Easy application, quick dry at 70oFApplication over old paint, minimum surface preparationLow solvent, low odor, easy clean-up

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MidMid--Quality Wall Paint Quality Wall Paint RequirementsRequirementsColor and hiding powerLow glossScrub resistance and cleanability3-4 years service lifeEasy touch-up, good color match

Example II: Aircraft TopcoatExample II: Aircraft TopcoatShelf life: > 1 year, heat age and freeze-thawCost - $100/galSpray application at airframe manufacturer or depot by professionalPot life > 4 hrs (at temperatures up to 90oF)Dry time at temperatures from 50 to 90oF:

Dry to remove tape: < 4 hrsDry hard: < 6 hrs

Application over epoxy primer

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Formulating StrategyFormulating StrategyI. Define Requirements During Coatings’

Life CycleRaw MaterialsMixing and BlendingStorageApplicationDrying / CuringShipping / InstallationProduct LifeDisposal

Interior Flat Wall Paint FormulationInterior Flat Wall Paint FormulationMATERIAL Pounds Gallons NVM-Lbs. NVM-Gals.

GRIND3.0% Cellulosic Thickener Solution 50.0 6.00 1.5Water 120.0 14.41Dispersant, 35% T.S. 8.0 0.81 2.8Surfactant 2.6 0.33Buffer 2.0 0.23Defoamer 2.0 0.27Preservative 1.0 0.12TiO2, Flat Grade 125.0 3.91 125.0 3.91Calcined Clay 175.0 9.55 175.0 9.55Calcium Carbonate 175.0 7.75 175.0 7.75SUB-TOTAL: 660.6 43.38 475.0 21.20 Grind to 4+ H.S.

LET-DOWN3.0% Cellulosic Thickener Solution 200.0 24.01 6.0Water 0.0 0.00

LATEX ADD:Vinyl Acrylic Polymer (55.0%) 201.0 22.21 110.6 11.42Defoamer 2.0 0.27Propylene Glycol 26.0 3.02Texanol 8.0 1.01Water 51.0 6.12 TOTAL 1148.6 100.03 585.6 32.62

PHYSICAL PROPERTIES

Wt./Gal.: 11.5% Solids, By Weight: 51.0% Solids, By Volume: 32.6% PVC: 65.0% PVC, TiO2: 12.0% Disp. Solids On Pigment: 0.6% C.S. on Latex NVM: 7.2

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Aircraft Topcoat FormulationAircraft Topcoat FormulationMaterial Pounds Gallons NVM-lbs NVM-Gals(Component A)Polyester polyol 238.0 29.9 200.0 50.0

(84% solids)Titanium dioxide 549.4 17.0 549.4 17.0DBTD catalyst 10.0 1.5 1.0 0.1

(1% in MEK)Surfactant 10.0 1.5 1.0 0.1

(1% in MEK)MEK 177.4 26.1 0.0 0.0

(Component B)Isocyanate 233.0 24.0 174.8 18.0

(75% solids)

TOTAL 1217.8 100.0 926.2 85.2

% solids, weight 76.1% solids, volume 85.2% PVC 20.0VOC, lbs/gal 2.6NCO/OH 1.1

HegmanHegman Grind GaugeGrind GaugeHegman

ScaleDepthin mils

012345678

0.50

1

2

3

4

1.5

2.5

3.5

Equivalent inmicrons

12.50

25

50

75

100

37.5

62.5

87.5

scraper

reading

dispersion

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Important Paint Formulation Important Paint Formulation ParametersParameters

Pigment volume concentration (PVC)Critical pigment volume concentration (CPVC)Solids content; non-volatile volume (NVV)Volatile organic compounds (VOC)CostStoichiometryVolume mix ratios (2 component coatings)

B

B

BB

BC

C

C

C

C

A A

A

A

A

A A

ABinder

Vehicle

Pigment/Filler

Volume solids (Non Volatile Volume Volume solids (Non Volatile Volume -- NVV)NVV)

%NVV = Volume of binder + Volume of pigment

Total volume of wet paintx100

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Pigment Volume Concentration (PVC)Pigment Volume Concentration (PVC)

PVC is the ratio, by volume, of allpigments & Filler

in the coating to total non-volatiles

Filler

Binder

Dry Film

PVC = Volume of (Pigment + Filler)

Total Volume of Dry Coating

Critical Pigment Volume Critical Pigment Volume Concentration (CPVC)Concentration (CPVC)

CPVC = the PVC where there is just sufficient binder to coat pigment surfaces and fill the voids between pigment particles.

At CPVC striking changes are observed in the properties and behavior of paint films.

Filler

BinderDry Film

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Critical Pigment Volume ConcentrationCPVC

PVC = 0 PVC > CPVC PVC = 1.0PVC = CPVCPVC < CPVC

PigmentBinder

( ) ( )VolumeBinderVolumePigmentVolumePigment

PVC+

=

Properties that change abruptly at Properties that change abruptly at the CPVCthe CPVC

Optical PropertiesLight scatteringHiding power efficiencyGloss / Sheen

Others PropertiesElectrical conductivityBlock resistance

Physical PropertiesDensityTensile Strength

Permeability Properties

PorosityBlistering

DurabilityWet Scrub ResistanceStaining

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Pigment Volume Effects on Dried Paint Pigment Volume Effects on Dried Paint

CPVC

Factors That Effect Packing Efficiency

1. Particle Size Distribution 2. Particle Shape or Shape Distribution

CPVC Depends onCPVC Depends onthe Packing Efficiencythe Packing EfficiencyPigments within BinderPigments within Binder

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Factors Determining CPVCFactors Determining CPVCParticle PackingParticle Packing

High PVC Low PVC

Factors Determining CPVCParticle Size - First Approximation

Q - Which packs more densely - large or small circles?

A - Void fraction the same in each case

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Factors Determining CPVCFactors Determining CPVCParticle Size Particle Size -- Other ConsiderationsOther Considerations

particle minimum layerof binder

Coated particle is 70% binder Coated particle is 30% binder

Also: Small particles pack less densely

Factors Determining CPVCFactors Determining CPVCParticle Dispersion Particle Dispersion -- TiOTiO22 in Mineral Oilin Mineral Oil

0.000.050.100.150.200.250.300.350.400.450.50

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Dispersant Level

CPV

C

Asbeck, JCT 49, 635, 59 (1977)

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Factors Determining CPVCParticle Porosity

Diatomaceous Earthan empty sphereCPVC = 0.18

Fumed Silicavery open structureCPVC = 0.23

Oil Absorption (OA) ValueOil Absorption (OA) ValueGrams linseed oil required to form a paste from 100 gram pigment.Oil first coats surface and fills voids; excess needed to turn moist solid into liquid.Depends on:

Surface area / Particle size (like CPVC)Packing - presence of voids / porosity (like CPVC)Wettability

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Significance of OA

Rough guide to surface area (dispersant demand, adsorption of other materials from liquid paint).Also, OA is related to cpvc …

% void fraction:• OA if oil• CPVC if resin

OA / CPVC Relationship:

[ ]( ) ⎟⎠⎞⎜

⎝⎛ ⋅+

=

5.931

1ρOA

cpvc

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Particle ShapeParticle ShapeMaterial Size, μm Shape

Titanium dioxide

Calcium Carbonate

Ground

Precipitate

Clays

Ground

Calcined

Silica

Diatomaceous

Talc

Mica

0.2 - 0.5

0.6 - 20

0.1 - 2

0.1 - 5

0.8 - 2

4 - 10

1 - 10

8 - 50

block

block

block, aggregates

plate

plate

irregular

plate and fiber

flake

Coating Life CycleCoating Life Cycle

Raw MaterialsMixing and BlendingStorageApplicationDrying / CuringShipping / InstallationProduct LifeDisposal

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Mixing and BlendingMixing and BlendingEase of additionOrder of AdditionEase of MixingHeat build-upFoamingShockingHealth & SafetyOdorDelivery to Storage / Use TankClean up

StorageStorageFreeze-Thaw StabilityHeat StabilitySettling of componentsPhase SeparationGel-FormationSpoilage

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ApplicationApplicationProfessional painter vs home ownerApplication Environment

Controlled (OEM) vs or On-siteInterior vs Exterior)

Method of applicationroller, slide, slot, blade, curtainbrush, spray, etc.

Delivery to ApplicatorRequired film thicknessSubstrate

Cleanliness, texture, porosityWaste and RecyclabilityEnvironmental regulations

Drying/CuringDrying/CuringDrying Conditions

Controlled (OEM) vs or On-siteInterior vs Exterior)

Sag and LevelingSubstrate Constraints

Temperature LimitsWarp

DefectsAdhesionEnvironmental regulations

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Product LifeProduct LifeAppearance

Color, gloss, opacityMechanical Properties

Hardness, flexibility, scrub resistanceSubstrate Protection

Corrosion, wearChemical Resistance

Stain, acid, baseEmissions

Indoor air qualityTouch-up and Refinish

Coating IndustryCoating Industry

33%27%

22%18%

Europe North America Asia Other

Total Value - $70.6 billion

Total Volume - 5 billion gal.

34%30%

21% 15%

Europe North America Asia Other

Global Coating Market Global Coating Market –– Yr 2000Yr 2000Current Current –– Approx. $80 billionApprox. $80 billion

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Coating Market Segments Coating Market Segments -- USUS

OEM Product CoatingsAutomotiveMarineAircraftMetal ContainersAppliancesMachinery and EquipmentWood FurniturePlasticsCoilOverprint

Architectural PaintsInteriorExterior

Special PurposeIndustrial MaintenanceTraffic PaintAuto Refinish

MiscellaneousRoof, Tank, DeckConcrete

Penetration of Waterborne Penetration of Waterborne Coatings Coatings –– US US

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% Penetration (1985)

41Special Purpose Coatings

80Architectural Paints

26OEM Product Coatings

% Penetration (2000)

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Resin/BinderProducers

AdditiveProducers

Distributors andResellers

ContractorsApplicators

Distributors andResellers

Spcifiers/End- Users

Solvent Producers

Pigment Producers

SpecialtyIntermediates

Formulators

Inspectors

Equipment

COATINGS INDUSTRY STRUCTURECOATINGS INDUSTRY STRUCTURE