Perfluoroalkoxy (PFA) is a type of synthetic fluoropolymer material that is used in a plethora of commercial and industrial applications – from food packaging to defense. PFA is considered to be a middle tier fluoropolymer that offers the most versatility in terms of application.Compared to PTFE and FEP, PFA has superior chemical resistance and anti-adhesion properties but lower resistance to abrasion. Fluoron’s services offer the ability for PFA linings tubing, and more to be made for custom applications within the aerospace industry. Fluoron’s product, Fluoroflex, is a PFA based material that delivers the best performance.
Temperature and Thermal Properties
From a temperature perspective, Fluoroflex is a versatile fluoropolymer because of PFA’s high temperature tolerance and properties as a thermoplastic. As such, PFA is able to repeatedly melt when heated and turn solid when cooled while still retaining its physical integrity. It also has a melting point temperature of 315°C, and maximum operating temperature of 260°C. Unlike PTFE, PFA can be melt processed – meaning it can be thermoformed to assume the shape of any custom tubing, piping lining or wrapper application.
In terms of thermal stability, PFA has a low thermal expansion rate and low thermal conductivity rate. The thermal expansion rate of 12 x 10-5 K-1 means that the material undergoes negligible expansion and contraction when exposed to a volatile temperature range. Unlike non-fluoropolymer materials used in high temperature settings, PFA will not experience warping, brittle deformation or cracking due to thermal cycling. The thermal conductivity rate of 0.2 W/(m*K) for PFA means that it is a poor conductor of heat, and a preferred insulator when it comes to localizing heat in parts of a system while deflecting it from other subsystems.
Chemical Inertness and Reactivity
Fluoron’s Fluoroflex PFA material combines chemical inertness and low reactivity. The fluorine within the PFAchemical bonds shields the outer perimeter of the material from permeation to fluid, thus allowing protection from highly acidic and highly basic fluids that may come in contact with it. The respective permeability constants of PFA for CO2, O2 and N2 are 273 Ng*cm/m2s, 637Ng*cm/m2s, and 91 Ng*cm/m2s mean that FluoroFlex also acts as an effective sealant to mitigate separation between fluids.These innate features allow FluoroFlex to be resistant to corrosion, resistant to weathering, and resistant to UV radiation. Common fluids that come in contact with PFA but do not risk corrosion are hydrochloric acid, bleach, sodium hydroxide and sulfuric acid.
Although not as abrasion resistant as PTFE based fluoropolymer products, PFA exhibits excellent mechanical properties in the form of tensile strength, flexibility, and non-wetting characteristics. PFA exhibits tensile strength of 27 MPa, roughly 4000 psi, meaning that it is highly shatter resistant, resistant to deformation in the presence of mechanical load and does not exhibit stress fractures at the same rate as conventional materials. The elongation rate of 310-360% exhibited by PFA allows for the material to perform under high mechanical strain without exhibiting signs of failure.The non-wetting rate of <0.05% for PFA is evident of its hydrophobic qualities, meaning that the material will not absorb any fluid nor introduce said fluid to a system that it is protecting. Compared to exotic metals, which tend to be used for their coveted mechanical properties, Fluoroflex is able to deliver similar quality at a lower price and significantly lighter weight.
PFA exhibits a dielectric constant 2.1, similar to that of PTFE’s dielectric constant of 2.0. This means that the material is useful for protective insulating electrical systems like power cables, electronic devices, and other wiring. PFA also has a surface arc tracking constant of greater than 300, which also means that it is not prone to discharging electricity – a coveted feature when dealing with independent electronic and electronic systems within a physically constrained environment. Overall, the electrical properties offered by PFA makes FluoroFlex a prime candidate for insulating safety critical aerospace systems and protecting them from electrostatic discharge that risks short-circuiting and ultimately failure.
Applications in Aerospace Subsystems
In the aerospace industry, FluoroFlex is best suited for custom lining applications, whether the application be a loose liner for a tank or a thermoformed liner for a fuel system. In caustic environments, linings ensure the longevity of safety critical components and subsystems within an aircraft. Examples include but are not limited to fuel lines, oil lines, and drinking and gray water lines. The commonality among these systems is that they require a specific purity level at the parts per million scale, and must be able to withstand the strain of aerospace specific environments. FluroFlex by Fluoron delivers these capabilities by leveraging the temperature volatility and inert qualities of PFA, which prevents corrosive liquids from causing component failure, and risking contamination from being within close proximity of other systems. In tandem with this, the mechanical and electrical properties ensure protection of aerospace systems from the harsh conditions and lack of maintenance within the realm of the upper atmosphere and deep space.