Conventional PTFE materials are not without some disadvantages. They are:
Sensitive to creep and wear
It cannot be processed by processing methods in the molten state, and suitable methods can often be unconventional and extended.
Difficult to join
High dimensional changes near the glass transition temperature.
Low radiation resistance
Corrosive and prone to produce toxic fumes.
Importance of fillers and additives to PTFE –
Adding fillers and additives can significantly improve the mechanical properties of PTFE, especially creep and wear rate. Commonly used fillers are steel, carbon, glass fiber, carbon fiber, graphite, bronze, steel, etc.
Glass fiber: Its addition will improve the creep performance and wear properties of PTFE by affecting its low and high temperature. In addition, glass-filled compounds perform exceptionally well in oxidizing environments.
Carbon fiber: Carbon fiber is essential for reducing creep, improving hardness, increasing flexibility and compression modulus. PTFE mixed with carbon fiber compounds has high thermal conductivity and a low coefficient of thermal expansion. Carbon fiber is inert to strong alkalis and hydrofluoric acid (glass fiber can tolerate both acids). These parts are ideal for making automotive parts such as shock absorbers.
Carbon: Carbon as an additive will help reduce creep, increase hardness, and improve the thermal conductivity of PTFE. The same results can be achieved by mixing PTFE and graphite and improving the wear resistance of carbon-filled compounds. These blends are ideal for non-lubricated applications such as piston rings in compression cylinders.
Bronze-filled PTFE: This compound has excellent thermal and electrical conductivity, making it ideal for applications that are subject to extreme loads and temperatures.
Advantages of adding fillers –
Fillers/additives are essential to increase the porosity of the PTFE compound, and therefore affect the electrical properties – it reduces the dielectric strength while increasing the dielectric constant and dissipation factor.
Fillers can significantly improve the performance of PTFE at both high and low temperatures.
The change in chemical properties depends largely on the type of additive used, however. Generally speaking, it also leaves a positive result.
PTFE Applications –
Typically, fluorinated thermoplastics are used for high-performance applications with high-temperature resistance, high purity, low-temperature, chemically inert, non-stick, and self-lubricating properties. Here are some of the most common uses for PTFE:
Engineering – Bearings, non-stick surfaces, valve seats, plugs, fittings, valves and pump parts.
Medical – Heart patches, cardiovascular implants, ligament replacements.
Chemical Industry – Coatings for pumps, diaphragms, impellers, heat exchangers, autoclaves, reaction vessels, tanks, containers, etc.
Automotive – Valve stem seals, shaft seals, gaskets, O-rings, fuel hose linings, power steering, transmissions, etc.
Electrical and Electronics – Flexible printed circuit boards, electrical insulation, etc.
Best Technologies for Processing PTFE –
PTFE's rigid polymer chain structure makes it extremely difficult to process with traditional methods such as injection molding and extrusion. Nonetheless, its extremely high melt viscosity and high melting temperature do not help. The ideal processing technologies for handling powder metallurgy are well suited for PTFE.
Sintering, compression molding, pressing, stamping or paste extrusion, hot stamping, machining, extrusion of pre-sintered powders on specialized machines.
Paste extrusion mixes PTFE with hydrocarbons, which are used to make it into tapes, tubes, and wire insulation. The hydrocarbons evaporate before the parts are sintered.
Operating range -200°C to 260°C.
FAQ –
1. Is PTFE carcinogenic?
A. PTFE has been shown to be toxic to human health because it contains a carcinogen called PFOA. However, there is no need to worry because PTFE non-stick coatings no longer contain this substance.
2. What is PTFE tubing used for?
A. PTFE tubing is most commonly used as laboratory tubing, where chemical resistance and purity are most important. PTFE has an extremely low coefficient of friction and is known as one of the most "slippery" substances known.
3. What kind of plastic is PTFE?
A. PTFE is a thermoplastic polymer that belongs to the class of fluoropolymers composed of carbon and fluorine atoms.
4. What is PTFE sheet used for?
PTFE sheet is used in various applications such as PTFE encapsulated gaskets and PTFE packings. It has excellent resistance to gases, water, chemicals, fuels and oils.
