PVDF and FEVE resin based coatings. What’s the difference?
Powder coatings are increasingly popular as the high performance coating choice! What's not to love - seriously good weathering and durability protection (meets and exceeds the performance requirements of AAMA 2605), superior scratch and mar resistance, and a significantly better environmental footprint when compared to liquid coatings!
All good, but it has to be said, sometimes there is some confusion, especially when it comes to the different resins used in high performance Fluoropolymer powder and liquid coatings. Read on for a basic guide to AAMA 2605 Fluoropolymer powder coatings.
Architectural coatings that meet and exceed the performance requirements of AAMA 2605 can be based around two different types of resin:
FEVE resin (fluoroethylene vinyl ether)
PVDF resin (polyvinylidene difluoride)
Most of us have heard about PVDF resins in traditional liquid paints. Liquid 70% PVDF, 2 coat+ paint sytems are based on PVDF resins. PVDF resin based powder coatings are also available, and these powders are also 2 coat systems. FEVE resins are used in many architectural grade powder coatings and due to their unique resin make up are single coat systems that give the same or better performance as a 2 coat system.
This is what the PVDF resin chemical structure looks like -
This is what the FEVE resin structure looks like.
Ultra-weatherability, durability, and chemical resistance are derived from the distinctive alternating fluorinated units. Let's get scientific for a moment. The FEVE resins are usually reacted with aliphatic isocyanates to form crosslinked FEVE coatings. FEVE based fluoropolymer coatings take advantage of the carbon/fluorine bond, which is extremely difficult to break. Carbon-fluorine bonds can absorb much greater amounts of UV energy and will keep this energy from affecting the weaker bonds/linkages in the FEVE resin polymer structure.
So what are the differences and similarities between FEVE and PVDF resins?
Both FEVE and PVDF resin based coatings are factory applied finishes, requiring a spray and bake application process. Both will meet and exceed the performance requirements of AAMA 2605. For this reason the same type of warranty is also available when applied to architectural aluminum by a registered applicator and both are available in solid and metallic or mica finishes. Powders are even available in a light texture.
However, there are some differences and this can be where confusion sets in.
Thermoset vs. thermoplastic
PVDF systems are thermoplastic. FEVE systems are thermoset. The thermoplastic PVDF resin will “remelt” under high temperatures and pressures while the FEVE resin is a thermoset system that will not “remelt” once it is correctly cured. These thermosetting properties also give the FEVE resins superior toughness and scratch and mar resistance.
Number of coats
PVDF based liquids and powders, must be a minimum of 2 coats. A primer coat is required to add protection and work with the top coat to give the desired levels of durability and protection. In fact the number of coats can depend on location, color and special effect required - plus performance. Kinda confusing.
FEVE based powders are single coat applications when applied to aluminum. The unique Fluorine-Carbon bond and thermosetting properties of the FEVE resin means the same (or better) levels of durability and protection are executed in a single coat. No primer or clear coat is required. Even for metallic/mica powder coatings.
Color and gloss
Both PVDF based systems and FEVE resin based powders retain their color and gloss extremely well and will meet and exceed the weathering performance requirements of AAMA 2605. However with FEVE based powder coatings higher gloss finishes are available. The PVDF resins are much more limited in the range of gloss they can achieve as the PVDF resin acts like a matting agent. Because the Carbon-Fluorine bond is part of the resin system in FEVE based systems there is no matting effect.
Manufacturers of PVDF based powders will tell you that this is the superior coating and will have data to prove it. Manufacturers of FEVE resin based powders will tell you that this is the superior coating and will also have data to prove it. The truth, as always, is somewhere in between. The fact is, both products work well, offer great protection and warranties and are an excellent coating choice. At IFS Coatings we use FEVE based resins, along with many of our competitors. We believe there are many, many more examples of FEVE resin based powder coatings out there than PVDF powder projects, and they have been shown to be successful time after time after time.
From a sustainability perspective, we know that FEVE resin based powders are a better choice. For architectural practices that claim to practice sustainable design, making the switch to powder should be a no brainer. Not only is solvent removed from the process as well as toxic compounds, less product and less energy is used in the application process and chrome (yes, it's not good for people or the environment) can be completely removed from the process. Most 70% PVDF liquid paints need a chrome based pretreatment AND a chrome based primer, especially to get a warranty. FEVE resin based powders will perform on top of both chrome and non-chrome pretreatments.
Navigating the world of architectural coatings and the various options out there can be tricky. We are here to help you, provide data you need, answer your questions and give you advice whenever you need it. Don’t hesitate to ask.
Talk to your IFS architectural specification expert. E: firstname.lastname@example.org