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Weathered Thermosplastic Polyolefin Roofing: Characterization, Surface Analysis and Best Practices for Coating

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Abstract
1) Characterization of TPO surfaces shows that contact angle is low for unweathered membranes but increases substantially as TPO weathers. (2) Measured by XPS, unweathered TPO membranes vary in surface chemical composition from manufacturer to manufacturer primarily in the ratio of polymeric material (i.e. TPO resin and E/P elastomer) to pigment. 3) Natural exterior weathering of TPO as measured by XPS atomic analysis causes a decrease in the carbon-rich areas and an increase in the metal oxide content at the surface likely by an oxidation mechanism. 4) Hydrophilic dispersants used in elastomeric roof coatings designed for weathered TPO provide better peel adhesion than coatings which contain hydrophobic dispersants. 5) Large particle size, low oil absorption extenders/pigments such as calcium carbonate should be used in coatings designed for application to weathered TPO to maximize adhesion performance. 6) Zinc oxide, a small particle size, high oil absorption pigment and others like it, should be avoided in coatings formulation when maximum adhesion to weathered TPO is desired. 7) Coatings adhesion can be increased by cleaning weathered TPO with commercial cleaners and powerwashing with sufficiently high pressure (i.e. 23000 psi).
Date
7/2012
Author(s)
Joe Rokowski
Page(s)
36-51
Keyword(s)
thermoplastic; polyolefin; weathering; membrane; TPO; coating


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