Weathered Thermoplastic Polyolefin Roofing ... - Roof Coatings · PDF fileWeathered Thermoplastic Polyolefin Roofing: Characterization, Surface ... Adhesion vs. Formulation Components

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Weathered Thermoplastic PolyolefinRoofing: Characterization, SurfaceAnalysis and Best Practices forCoating

Dow Chemical Information

Coating

Joe Rokowski,RCMA Symposium 7,17,2012

Dow Construction Chemicals

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Agenda

• TPO Basics

• Surface Analysis

• Coatings Formulation Influences


• Surface Cleaning

• Summary

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TPO Basics

•Single ply waterproof membrane

•Thermoplastic

•Scrim Reinforced


•White = Energy star Compliant

•Heat weldable = installation ease

•Economical

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Basic TPO Processing


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TPO Roofing History

• TPO membranes for roofing began in Europe inlate 1980’s targeting plasticizer & halogen freeproducts

• US introduction in 1992

• Significant US market penetration 2000


• Significant US market penetration 2000

• 2005/2006 US growth rates 25-35% !!

•TPO = 40-50% less expensive than conventionalroofing membranes.

• And its White !!

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Composition of TPO Polymer

• Polypropylene (Tough/Hard, no functionality)

+

• EPR= Ethylene/propylene rubber


Or

EPDM Rubber

(Both are flexibilizing agents with somefunctional groups)

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Formulation TPO Roof Membrane:

•Pigments (TiO2, CaCo3)

• Fire retardant: Mg(OH)2 , brominated organics,Aluminum TriHydrate

• Crosslinker: peroxides, etc.


• Crosslinker: peroxides, etc.

• Antioxidant: phenols, amines, phosphites

• Lubricant/Processing aids

• UV absorbers

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TPO Failure Mechanism

• Over time, on a roof: UV, H20, Thermalcycling, soil, etc.

- Slow surface erosion occurs, eventuallyrevealing reinforcing scrim


revealing reinforcing scrim

- Micro cracks develop

- Dirt decreases reflectance, increasestemperature

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Early TPO Issues

Early Failures due toformulation ingredients (e.g.halogenated fire retardants)and compounding issueshave largely been corrected.


have largely been corrected.

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DOW’s Role in Low Slope Roof Coatings

• Emulsions Polymers into Pigmented Coatings

• High exterior durability – roof life extension

• White for Energy Savings


• Must have excellent wet adhesion

• We understand how roof substrates fail

• Goal: Improve adhesion of coatings toweathered TPO Roofs.

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Why Coat TPO Membranes ?

-All exterior roofs and coatings eventuallydegrade and have a finite service life

- Provide an alternative to tear-offs

- A retrofit/maintenance solution


- A retrofit/maintenance solution

- TPO is waterproof

- Coatings do not replace waterproofing-

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Conventional commercial elastomeric roofcoatings in their recommended pigmentedformulations generally don’t adhere well to

Typical Elastomeric Roof Coating


formulations generally don’t adhere well toNew or Weathered TPO.

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Current Products: Adhesion to Weathered TPO

Dry Adhesion

Adhesive Failure


Wet AdhesionAdhesive Failure

Poor Adhesion

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Difficulty of Coating TPO Roofing

• Lack of functional groups

• Low surface energy

• Poor wettability

• Difference in the type of TPO on the


• Difference in the type of TPO on thesurface whether semi-crystallineamorphous

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Difficulty of Coating TPO

Contact Angle or Surface Wettability


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Contact Angle Measurements

TPO:

AverageContactAngle

Percent Differencevs. Unweathered

TPO Membrane #1 New 48 ---

TPO Membrane #1 5 Year Weathered 71 + 36 %






TPO Membrane #3 6 months WOM* 68 + 55 %

Elastomeric Coatings:Standard ERC #1 67 ---Hydrophobic ERC #2 44 ---New Coating w/ Weathered TPOAdhesion 65 ---

* Atlas Weather-O-Meter

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Surface Characterization

Contact Angle:

New = 32-48o

Weathered = 66-71o !!!!!!


Weathered = 66-71 !!!!!!

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TPO Membrane Differences

• Recent research by the National Roofing Contractors

Association (NRCA) found that there are significantdifferences between TPO membranes currently beingsold in the U.S. The effects of some of these differencesare still unknown at this time. NRCA believes otherdifferences will have notable effects on the usability and


differences will have notable effects on the usability andlong-term field performance of TPO membranes. Sincethese types of roofs have either had a history ofproblems or not enough of a track record, we are closelywatching the performance of these products before weinstall them.

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Surface Analysis

• XPS = X-Ray Photoelectron Spectroscopy

• It measures atomic elements on the surface of amaterial

• How far down? About 10 nanometers or 1/100th


• How far down? About 10 nanometers or 1/100of a micron

• Light elements like Hydrogen and Helium areexcluded.

• C = polymer

• O, Al, Si = metal oxides and pigment (Ti)

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TPO Surface Analysis

TPO #1 Al C Ca Cl O S Si P N

New 1.1 90.2 0.3 0.2 3.9 0.1 2.7 0.2 1.3

6 MonthWeathered 2.8 76.2 0.4 0.2 13.3 0.4 4.7 0.2 1.7

1Yr Weathered 3.7 69.1 0.5 0.4 17.1 0.3 6.8 0.3 0.2



New 0.9 90.3 0.2 0.3 6.0 0.2 1.8 0.3

6 MonthWeathered 1.9 72.8 0.4 0.4 14.7 0.4 7.3 0.3 1.8

1 Yr Weathered 2.0 57.7 0.2 0.3 19.2 0.2 20.1 0.3

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New 0.8 87.1 0.2 0.2 6.5 0.4 1.2 0.2 3.2

6 Month ExteriorWeathered 2.6 72.4 0.4 0.4 15.2 0.3 6.8 0.3 1.5

1Yr ExteriorWeathered 4.0 64.1 0.5 0.5 20.2 0.3 7.9 0.3 1.8

TPO Surface Analysis


Weathered 4.0 64.1 0.5 0.5 20.2 0.3 7.9 0.3 1.8


New 0.9 80.2 0.4 0.4 10.0 0.2 5.4 0.3 2.0

7Yr ExteriorWeathered 4.9 54.3 1.0 0.3 26.2 0.2 10.9 0.6 0.8

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Surface Characterization

Assumption:

New TPO = smooth, polymer rich,hydrophobic


Weathered TPO = rough, pigment rich, andrelatively hydrophilic

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Formulation

• Typical Elastomeric Roof Coating

• 40% PVC/50% VS

• No zinc oxide


• Slightly higher TiO2 than normal

• 1 gal/square as basecoat plus 1gal/square as topcoat

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INGREDIENTS: POUNDS:

GRIND Water 145.00TAMOL™ 851 5.70Aqueous Ammonia(28%) 3.00BYK 012 2.00Omyacarb 12 392.50TiPure R-960 62.50

:LETDOWN BYK 012 3.00

RHOPLEX EC-3100 (55%) 490.10

Formulation


RHOPLEX EC-3100 (55%) 490.10Water 13.90UCAR™ Filmer IBT 6.00SKANE™ M-8 3.00Propylene Glycol* 10.00Dow hydroxyethyl cellulose 4.00

1141.70

PVC= 40% % Volume solids =50%% Weight Solids = 64.2%

pH = 10.0

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ERC with Adhesion to Weathered TPO

• DOW Commercial name =

Rhoplex™ EC-3100


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Pigment Dispersant

• Dry Pigments are supplied in an agglomeratedpowdered form

• Mechanical shearing in water physically separatesthe clumps

• Water soluble dispersants adsorb onto and coat


• Water soluble dispersants adsorb onto and coatpigments to keep them separate to maintain smallincrease act efficiently

• Use levels are 0.3 to 1.0% on pigment

• Impact performance

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Dispersant Description Neutralizer MW HanschValue

A Poly - Acid Sodium(Hydrophilic)

High -2.2

B Acid/Copolymer Sodium(Hydrophobic)

High +0.3

Pigment Dispersant Description


(Hydrophobic)

C Poly Acid Ammonia(Hydrophilic)

Low -2.2

D Acid/Copolymer Ammonia(Hydrophobic)

High + 0.3

E Poly Acid Sodium(Hydrophilic)

Low -2.2

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Adhesion vs. Dispersant Hydrophobicity

Hydrophilic


Hydrophobic

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Adhesion vs. Formulation Components

• Very small particle size pigments have highersurface area than large particle size pigments

•High oil absorption pigments need more polymer tobind to than low oil absorption pigments


bind to than low oil absorption pigments

• This reduces the amount of “free polymer” availablein the formulation

•Does this impact adhesion of a coating?

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2

2.5

3

A

D

H

E

S

I

Peel Adhesion vs. Formulation Ingredients

Adhesion vs. Formulation Components


0

0.5

1

1.5

W/ ZN OX NO ZN OX CACO3 UF CACO3 3µ CACO3 5µ

I

O

N

P

L

I

Formulation Difference

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Swell the amorphous boundary layer, allowpenetration, bonding and adhesion ?

1) IPA / VM&P Naptha 50/50

Solvent Cleaning of TPO


2) Jeffsol / Propylene Carbonate = VOCExempt

Flammability, Odor ?

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Solvent Cleaning: Current Products &Formulas: Adhesion to New TPOMixed Results: Some Adhesive Failure, Some Delamination Failure

Dry Adhesion

Wet Adhesion


Wet Adhesion

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Solvent Cleaning Current Products & Formulas:Adhesion to Weathered TPOMore Mixed Results

Dry Adhesion

Wet Adhesion


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Description Chemistry Adhesion PLI /

Failure

No cleaning --- 0.3 / Adhesive

Water powerwashing --- 0.6 / Adhesive

Cleaner 1 + Phosphate and 1.6 / Cohesive

Adhesion Method vs. Surface Treatment


Cleaner 1 +

powerwashing with

water

Phosphate and

nonionic surfactant

1.6 / Cohesive

Solvent wipe 1 Isopropanol &

VM&P Naptha

50/50

2.2 / Cohesive

Solvent wipe 2 Jeffsol/ PM 50/50 2.0/ Cohesive

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Al C Ca Cl O S Si P NTPO 1 New 1.1 90.2 0.3 0.2 3.9 0.1 2.7 0.2 1.3TPO 1 YrWeathered 3.7 69.1 0.5 0.4 17.1 0.3 6.8 0.3 0.2TPO 1 , 1 YrWeatheredCleaner 1 1.0 83.2 0.4 0.3 10.5 0.3 1.6 0.2 2.3

Surface Analysis Before and After Cleaning


Cleaner 1 1.0 83.2 0.4 0.3 10.5 0.3 1.6 0.2 2.3

Al C Ca Cl O S Si P NTPO 2 new 0.9 90.3 0.2 0.3 6.0 0.2 1.8 0.3 ---TPO 2 1yrweathered 2.0 57.7 0.2 0.3 19.2 0.2 20.1 0.3 --TPO 2, 1 YrWeathered,Cleaner 1 0.8 86.5 0.3 0.3 5.7 0.1 3.0 0.2 3.1

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Adhesion Method vs. Cleaning Method


®Adhesion to New and Weathered TPO:New Emulsion Polymer

New TPO WeatheredTPO

Dry Adhesion

Wet AdhesionAdhesive


Wet AdhesionAdhesive

Delamination

®Mechanism of Adhesion

• Coating hydrophobicity must match thehydrophobicity of the weathered TPOsurface i.e. allows coating to effectivelywet the TPO surface

• Adhesion chemistry must be present in


• Adhesion chemistry must be present inthe polymer to adhere to sites madeavailable by weathering

• Formulation ingredients and surfacepreparation must be selected to optimizeadhesion

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TPO• Contact angle starts low but increases substantially as TPO weathers.• New TPO membranes vary in surface composition primarily in polymeric topigment ratio.• Exterior weathering of TPO via XPS/atomic analysis decreases surfacepolymer and increases surface pigment at the surface.

Conclusions


Coatings:• Match the contact angle of the coating and the substrate• Hydrophilic dispersants better than hydrophobic dispersants to improveadhesion• Large particle size, low oil absorption extenders help to maximize adhesion .• Adhesion can be increased by cleaning weathered TPO with commercialcleaners and powerwashing with sufficiently high pressure (i.e. ≥3000 psi).

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Thank You

Questions ?


Questions ?

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Weathered Thermoplastic Polyolefin Roofing ... - Roof Coatings · PDF fileWeathered Thermoplastic Polyolefin Roofing: Characterization, Surface ... Adhesion vs. Formulation Components