Q: We have heard that FEVE (fluoro-ethyl-vinyl ether)-based polymers are the only process-friendly fluoro powders that can meet the AAMA 2605 architectural standard (10 yrs durability). Can other fluoropolymers that are available in powder form (ETFE, PTFE) be used for AAMA 2605 applications?
A: PTFE (poly-tetrafluoroethylene) cannot be used as a film former in powder coatings because of its physical properties. The melt point of PTFE is about 327°C, and it isn’t a very sharp melt point. My understanding is that it has to undergo pressure as well as heat to form a film. Architectural substrates could never take this heat.
The melt point of ETFE (ethylene-tetrafluoroethylene) is somewhat lower, around 225°C, but still rather high for an aluminum substrate. PVDF (polyvinylidene difluoride) has been used as a polymer for exterior durable powder coatings. It’s a thermoplastic and is tricky to process. The crystallinity of PVDF changes in the extruder, and a managed cooling period is required after compounding. This makes FEVE a better choice, in my opinion. It’s more process forgiving.