Page 198 - CW E-Magazine (26-9-2023)

Special Report

Ultra-weatherability, durability and
chemical resistance

PVDF FEVE
Liquid 100% FEVE
(70% PVDF) Powder
2+ coats Single coat

Thermoplastic Thermoset (better
scratch resistance)
Bright metallic Wider range
finishes possible of gloss;
metallic finishes
challenging

For hyper-durable applications, usage
of liquid coatings has been quite
prevalent, especially for the most strin-
gent of specifications. This is typically
based on 70% PVDF liquid coatings
(30% acrylic). Hyper-durable powder
coatings are increasingly recognised as
a relevant alternative to liquid PVDF.
The powder technology is also based on
fluoropolymer technology (i.e.,fluoro
ethylene vinyl ether, FEVE) and has
some advantages:
It achieves the same performance in
a single coat;
The thermosetting properties of
FEVE-based powders mean far
superior scratch resistance and a signi-
ficant reduction in susceptibility
to dirt; and
PVDF resin acts like a matting
agent and hence PVDF coatings are
available today. These coatings need to AAMA 2605 requires aggressive much more limited in the range of
meet architectural standards that may 2,000 hours cyclical salt spray test. gloss they can achieve. With FEVE
vary from region to region – American It also requires colour and gloss powder coatings, a wider range of
Architectural Manufacturing Associa- warranty of 20-25 years, depending gloss finishes are available, though
tion (AAMA) in the US and Qualicoat on the project requirement. These there are some challenges in getting
specifications in Europe. are used for exterior applications metallic finishes.
on high value residential buildings,
As highlighted in figure below, as monumental buildings, etc. Due to these advantages, there is
we move from left to right, the stan- Stringent performance requirement increasing demand for hyper-durable
dards become more stringent: for architectural coatings powder coatings for architectural as
AAMA 2603 compliance needs salt well as in ACE segment.
spray testing of 1,500 hours and has AAMA* AAMA AAMA
relatively relaxed weathering re- 2603 2604 2605 Powder coatings have been the
quirement. These are primarily used preferred coating for aluminium sub-
for interior applications. strates in Europe for decades. Europe

198 Chemical Weekly September 26, 2023

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