Low-VOC Fluoropolymer
Highly Weatherable Restoration
Coatings for Building
by Kurt Wood,
Ron Partridge, and
Ravi Gupta†
Arkema Inc.*
Highly weatherable, 70% PVDF fluorocarbon finishes are among the most popular
coatings for exterior architectural metal, but when a need arises to make repairs or change
colors, the options for restoration paints are often rather limited. Nonfluorocarbon restoration paints will not match the original PVDF finish in terms of color stability. Many of the
fluorocarbon restoration paint options can have their own drawbacks, such as high VOC,
adhesion issues over PVDF finishes, and potlife/material handling issues for systems which
are two-component. We present here new studies to adapt PVDF-acrylic hybrid latex technology to the needs of the building restoration market. New one-pack formulations achieve
outstanding weatherability and excellent wet and dry adhesion to new and aged PVDF finishes, at VOC levels in the 100 g/L range. Second generation latex materials under development are showing similar adhesion properties, in formulations meeting West Coast 50 g/L
VOC requirements.
INTRODUCTION
Fluoropolymer-based coatings such as 70% poly vinylidene fluoride
(PVDF) finishes are among the most popular coatings for exterior architectural
building profiles, 1 including roofs. Coatings based on such resins are resistant
to degradation by UV and environmental factors, and thus have superior durability and color fade resistance, compared to coatings made from nonfluorocarbon resins. Not infrequently, metal roofs and associated components coated
with PVDF finishes may require color change to keep abreast of changing design trends, or to reduce building energy costs by installing “cool roof” reflective coating systems. In some other cases, the seams and joints of metal roofs
may fail due to moisture and thermal cycling, thus requiring restoration.
The options are often limited for restoring PVDF-coated metal roofs with
field-applied coatings. The faster degradation of the binder in nonfluorocarbon restoration paints means that they will not match the original PVDF
finish in terms of color stability. Many of the fluorocarbon restoration paint
options can have their own drawbacks. A good example is two-component,
fluoropolymer-based solvent coatings crosslinked with polyisocyanates.
Presented at the 2009 Coatings Tech Conference, sponsored by NPCA/FSCT, April 28-29, 2009, in
Indianapolis, IN.
†Author to whom correspondence should be addressed.
