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Use of accelerated weathering testing to reduce risk for new topcoat standards and specifications

Numerous industry studies have shown a lack of correlation between outdoor weathering performance in Florida, and performance in common accelerated weathering tests-- particularly when multiple types of resins are being compared. No single accelerated weathering test exists that can predict the outdoor performance for every type of resin in every color. 

Product Number: 51218-168-SG
Author: Kurt Wood
Publication Date: 2018
Industry: Coatings
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$20.00
$20.00

Numerous industry studies have shown a lack of correlation between outdoor weathering performance in Florida, and performance in common accelerated weathering tests-- particularly when multiple types of resins are being compared. No single accelerated weathering test exists that can predict the outdoor performance for every type of resin in every color. For this reason, when creating new standards and specifications for long lived exterior coatings, it is important to critically examine accelerated weathering data, before setting accelerated weathering requirements that will be used to qualify coating systems. If it is possible to limit a standard to a single well-studied resin chemistry, with accelerated weathering requirements based on the performance in one or more reference colors-- such as is done for SSPC Paint 36-- then risk for coating suppliers and end-users can be reduced dramatically. We will illustrate this principle for waterborne poly(vinylidene fluoride) (PVDF) fluoropolymer topcoats, using new weathering data from commercial and lab formulations. The results are sometimes surprising. For instance, for some darker colors, the coating color fade and chalk resistance in Florida, as a function of PVDF level, is better predicted in fluorescent cabinet testing by using the harsher UVB313 bulbs, rather than the UVA-340 bulbs which closely match the UV part of the Florida solar spectrum.

Numerous industry studies have shown a lack of correlation between outdoor weathering performance in Florida, and performance in common accelerated weathering tests-- particularly when multiple types of resins are being compared. No single accelerated weathering test exists that can predict the outdoor performance for every type of resin in every color. For this reason, when creating new standards and specifications for long lived exterior coatings, it is important to critically examine accelerated weathering data, before setting accelerated weathering requirements that will be used to qualify coating systems. If it is possible to limit a standard to a single well-studied resin chemistry, with accelerated weathering requirements based on the performance in one or more reference colors-- such as is done for SSPC Paint 36-- then risk for coating suppliers and end-users can be reduced dramatically. We will illustrate this principle for waterborne poly(vinylidene fluoride) (PVDF) fluoropolymer topcoats, using new weathering data from commercial and lab formulations. The results are sometimes surprising. For instance, for some darker colors, the coating color fade and chalk resistance in Florida, as a function of PVDF level, is better predicted in fluorescent cabinet testing by using the harsher UVB313 bulbs, rather than the UVA-340 bulbs which closely match the UV part of the Florida solar spectrum.

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