Fluoropolymers are polymers (plastics) whose chemical structures are made of carbon and fluorine bonds. These bonds allow for high performing mechanical and chemical properties. The qualities for fluoropolymers include but are not limited to enhanced tensile strength, abrasion resistance, flame retardance, low friction, corrosion resistance and more. Their vast range of truly unique properties allow fluoropolymers to be an economical solution in many applications – especially the aerospace industry. Fluoropolymers can exist in many forms, from large diameter heat shrink tubing for wire harnesses, to custom jackets thermoformed to aircraft components that are prone to weathering. Of all the fluoropolymers that exist on the market, Polytetrafluoroethylene (PTFE) is the most well known. Fluoron’s carbon reinforced PTFE, Fluorostat, is infused with graphite to deliver the highest quality anti-static and wear resistant performance. Unique properties are as follows:
Temperature and Thermal Properties
The fluorocarbon bonds within the FluoroStat material are responsible for its strength and other qualities. It has a melting point temperature of 327°C, minimum operating temperature of -268°C and maximum operating temperature of 260°C. It also exhibits high thermal stability over a wide range of temperatures, another feature attributed to its fluorocarbon bonds. Its coefficient of thermal expansion is 151 x 10^-6 per °C, meaning that there is virtually no fluctuation in size of the material when within its specified temperature range. Although PTFE has a high melting point, it does not melt in the conventional context and remains in a highly viscous form when melted. Therefore, it cannot be traditionally shaped using custom injection molding techniques because it does not flow. However, PTFE can be cold-formed into custom shapes via a process called compression molding. Fluoron offers a proprietary process where FluroStat can be welded into custom shapes dependent upon application.
Chemical Inertness and Reactivity
Fluorostat’s inertness is due to the stability of its chemical structure. The stability of its fluorocarbon bonds enable the material to withstand being submerged in harsh chemicals, like acids and bases, that cause corrosion within systems. The resistance to corrosion found in PTFE coincides with its wide temperature range, meaning that it can withstand corrosion at cold temperatures, where other materials become brittle and break, as well as high temperatures where conventionally used materials are prone to melting. Compared to legacy materials, like exotic metals, that are used to withstand chemically harsh conditions – a fluoropolymer such as PTFE is cheaper in price and offers sustained longevity, thus lending itself as a superior solution.
Mechanical Properties
With the low friction, high crystallinity, and non-wetting qualities of PTFE, FluoroStat is a jack-of-all trades material with all that it offers. PTFE has a friction coefficient of 0.05 to 0.10, making it the third lowest of any solid surface. As such, this makes for a smooth, wear-resistant surface that is able to resist damage from weathering. The high crystallinity of PTFE is a result of its dense chemical structure. As such, this allows it to have relatively high impact resistance and hardness to external obstructions.Its tensile strength of 30 Mpa in comparison to its further proves this quality. PTFE can also have external materials added to reinforce its mechanical properties. PTFE’s non-wetting feature is attributed to the hydrophobic quality of the fluorocarbon bonds in the molecule. As such, the absorption rate of PTFE is 0.010%.The absorption rate also holds true for other fluids such water, oil, and gas that can permeate through safety critical systems and ultimately cause them to fail. This guarantees that any material protected by Fluorostat will not be affected by moisture related defects.
Electrical Properties
In terms of electrical properties, Fluorostat leverages PTFE’s dielectric constant of 2.0 and the anti-static benefits of being carbon reinforced. The low dielectric constant allows for the material to be used as a protective insulator for electrical devices and wiring. However, when traditional PTFE is introduced to electrical systems, the slightest amount of static electricity can short-circuit electronic systems and cause them to fail. Since traditional PTFE is a strong insulator, it does not allow for electricity to conduct throughout the material. Therefore, when charged electrons are introduced to the material, they do not move and statically compound until discharged. This is especially problematic in aerospace applications where electronics are inaccessible once vessels are deployed, thus making maintenance very limited because of elapsed lead-time for a vehicles return, or non-existent if a vessel is meant to stay in space for an extended period of time.
When carbon (graphite) is appended to the chemical structure of PTFE, it becomes less prone to static buildup because this allows for electrons to freely move throughout the material and discharge in safer ways. Thus, FluoroStat delivers added benefits over traditional, non-reinforced PTFE.
Applications in Aerospace Subsystems
In the realm of aerospace, FluoroStat is best applied as a jacket, or lining. The purpose of a jacket is to act as a protective covering that is sealant, and resistant to weathering from outdoor environments. The mechanical and electrical properties of FluoroStat, such as tensile strength, low friction and anti static are exemplary qualities in this respect. It is able to withstand the volatile weather conditions of the upper atmosphere and radiation introduced in space applications. As such, FluoroStat jackets are used for aerospace components such as O-Rings, mechanical air bearings, and nosecaps. The conditions of deep space and the upper atmosphere also put stress on other critical aerospace systems, such as fuel lines, water lines, and air lines. Fuel lines in aerospace applications are not prone to maintenance due to the nature of their deployments, thus being outfitted with materials that guarantee holistic sealing, and non-contamination of fuel lines is safety critical.Custom linings solve this issue by acting as an impermeable barrier between the fluid within a line, and the material that the fuel line is made out of. Fluorostat’s chemical inert qualities and chemical resistance to corrosion align with this heavily because it guarantees that unwanted material cannot enter a fuel system and corrupt its purity, while also assuring that caustic fuel fluids do not leave the system. This holds true for water and air lines that interact with passenger(s) within an aircraft, who are operating within the scope of finite resources aboard an aircraft.
