The processing techniques for fluoropolymers can be divided in four main groups, depending on the nature of polymer.
PTFE Fine powder and granular
The majority of PTFE’s have extremely high melt viscosities, eliminating the possibility of processing them by conventional thermoplastic techniques. Most PTFE processes involve a cold forming cycle, generally followed by a sintering cycle. Thanks to the fibrillating nature of PTFE fine powder, it can be paste extruded and sintered to tubes, profiles and wire insulation, or un-sintered paste extruded PTFE can be formed to tape or stretched to expanded PTFE, used in applications such as gaskets and membranes. PTFE granular can be molded into stocks shapes or finished parts by ram extrusion or molding (Isostatic, automatic, compression molding). The basic stock shapes are machined into the desired shape after sintering.
(FEP,PFA,MFA, ETFE, ECTFE, PVDF, EFEP….)
These resins can be processed by standard melt-processing techniques such as injection, transfer and blow molding, extrusion and rotational molding. The high melt viscosity of these resins may require more powder and higher pressure rating equipment. The shear sensitivity of these resins require lower processing speeds than non-fluorinated polymers. To improve the extrusion speed of fluoropolymers, draw-down extrusion is often applied.
Processing of fluoroelastomers involves several steps: Compounding, where fillers, pigments and additives to improve properties, together with crosslinking curatives are mixed with the fluoroelastomer. Conversion of the compound into a shape, or component, for example, by extrusion or molding Vulcanization, whereby the polymer molecules become crosslinked, which fixes the shape Post curing to complete and optimize the formation of crosslinks
Dispersions and coatings made with Fluoropolymers
Uses for fluoropolymer dispersions fall into general categories of coating, impregnation and spraying. After applying a dispersion on a substrate, excessive dispersion is removed, the substrate is dried, “baked” to remove organic wetting agent(s) and then sintered to coalesce the polymer particles.
Caution: Molten for fluoropolymers, especially fully fluorinated fluoropolymers, are corrosive to most metals. Wherever fully fluorinated fluoropolymers are processed above their melting point the equipment must me made of corrosion-resistant high nickel/low ferrous alloys to avoid equipment damage and to avoid metal contamination in the processed parts.