Canadian Finishing & Coatings Manufacturing Magazine Jan/Feb 2023 - 39

PAINT AND COATINGS MANUFACTURING: POWDER RESINS - FEVE
HIGH RISE RESINS
The effects of particle size and distribution on surface appearance and the mechanical
properties of Fluoroethylene Vinyl Ether (FEVE) powder systems
BY CONNIE PRZESLAWSKI
Fluoroethylene Vinyl Ether (FEVE) Resins and
Application
T
he development
of large, exterior structures
has prompted the need for coatings capable of
withstanding the harsh elements of nature. As manmade
structures reach new heights, exterior coatings
have advanced to protect these massive structures for years
while maintaining the intended aesthetics of the consumer. The
leading technology for these desired coating properties is found
in fluoropolymer resin systems.
Fluoropolymers have been used in exterior coatings for
decades due to their excellent physical properties for longterm
exterior durability. Thermoset fluoroethylene vinyl ether
(FEVE) resins were developed as an alternative to thermoplastic
fluoropolymer resins. Figure 1 shows the chemical structure
of a FEVE copolymer. The alternating copolymer provides the
structural stability required for long-term weatherability and
chemical resistance. In addition, the fluoroethylene shields the
vinyl ether segments from UV degradation.
In contrast, the vinyl ether provides the copolymer with crosslinking
sites and solubility. As a result, the vinyl ether provides
the FEVE resins with excellent hydroxyl functionality that can
be incorporated into a wide variety of coatings. Table 1 displays
the general properties of FEVE resins. Multiple case studies
have been reviewed, and it has been observed that FEVE-based
topcoats also protect the underlying coatings from corrosion.
Overall gloss retention results in brilliant colour retention and a
fresh appearance over the years (Table 2).
Particle Size and Powder Coating Systems for FEVE
Resins
In contrast to liquid systems where consideration of raw
materials' order of addition must be observed, the preparation
process plays an essential part in the final coating's appearance
and performance. Powder coating requires meticulous attention
to processing parameters during compounding and powder
Fluorine Content
OH Value
COOH Value
25-30 wt.%
47-170 mg KOH/g
0-15 mg KOH/g
Molecular Weight Mw = 15,000-1,000,000+
Specific Gravity
1.4- 1.5
Morphology
Decomposition
Temperature
Glassy (Tg = 20-50°C)
240-250°C
Table 1: General Properties of FEVE Copolymer
milling for optimal powder application and coating performance.
Each powder processing step's variables depend on raw material
properties and formulation chemistry. Pre-mixed powder
samples are fed thru extrusion, where materials are dispersed
and homogenised into a brittle, compounded flake. After
extrusion, the flakes are milled and sieved to specific particle
sizes and distribution to achieve optimal film properties after
electrostatic spray and thermal cure (Table 3).
Many studies on powder coating particle size have outlined
the benefits of selecting a particle size and distribution that
optimises the appearance and properties to the applicator's
needs. Powder coating systems come in a variety of particle
sizes and distributions depending on application and
performance expectations. Investigations into achieving the
high specifications for exterior topcoat systems prompted
evaluations of how particle size and particle size distribution
can influence the appearance and performance of FEVE powder
topcoats utilised for exterior structures.
FEVE powder systems that had particle sizes below 25
microns behaved similarly to fine powders, resulting in poor
Figure 1: Alternating structure of FEVE resin.
January/February 2023
39
Canadian Finishing & Coatings Manufacturing Magazine Jan/Feb 2023

Table of Contents for the Digital Edition of Canadian Finishing & Coatings Manufacturing Magazine Jan/Feb 2023
