PTFE CG25 (Polytetrafluoroethylene + 25% Carbon-Graphite)

PTFE technical characteristics

As written before, Polytetrafluorethylene counts on extremely high technical characteristics and thanks to this factor, it is positioned between the high-performance thermoplastic materials. Great chemical resistance, excellent sliding properties, totally anti-adhesive, good temperature range resistance, these are only few of main polytetrafluorethylene characteristics, which we will see only here above.

Thermal properties

Polytetrafluorethylene thermal resistance goes from -260°C to +260°C, with a short range up to 300°C. There are only few materials with such a high thermal resistance. It is anyway important to know that PTFE performance at high temperature depends on load and stress too. Moreover, thermal dilatation is important to be considered during final components design, as a critical factor which could determine application results.

Water absorption

Polytetrafluorethylene suffers no water absorption at all, even after an immersion test period according DIN 53472/8,20.

Sliding properties

Another amazing polytetrafluorethylene property is its very low coefficient of friction, the lowest among all solid materials. Moreover, static and dynamic friction coefficient are theoretically the same, this good combination allows a zero stick-slip effect.

There properties are unchanged even under 0°C, only over the 20°C we can begin to notice some lower results.

Sliding properties stands still even with fillings.

Wear resistance

The wear resistance of pure polytetrafluorethylene is relatively low. The reason is that polytetrafluorethylene molecules, due to their complete enclosure by fluorine atoms, are capable of developing merely minimal intermolecular interaction.

A significant improvement of wear resistance is achieved thanks to fillers, such as carbon, graphite, glass, carbon fibres, bronze and organic agents.

Mechanical properties

Polytetrafluorethylene cannot count on excellent mechanical properties, such as other polymers. Anyway, polytetrafluorethylene can be improved by the addition of fillers, such as glass fibres, carbon or bronze.

Chemical and physical resistance and fire behaviour

Polytetrafluorethylene is chemical inert to almost all known acids. Generally, we can affirm:

• Neither solvents like alcohols, esters and ketones nor aggressive acid change the properties of polytetrafluorethylene ;
• Merely when used in coolants (ex. Freon) a reversible 4-10% increase in weight has been measured;
• A chemical reaction (browning) of polytetrafluorethylene only occurs with melted or dissolved alkali metals;
• At high temperatures and pressures polytetrafluorethylene reacts with elementary fluor- and chlorotrifluoride;
• Monomers like styrene, butadiene or acrylonitrile can penetrate PTFE in small amounts, and in the event of conditions triggering a spontaneous polymerization, this may lead to swelling of the material.

PTFE has outstanding light, weather and steam resistance. Moreover, we specify that it is not resistant to radiation – a long exposure could deteriorate the material.

Polytetrafluorethylene shows a great fire behaviour. It is tested that fluoropolymers can hardly be burnt. Polytetrafluorethylene is classified according UL94 V0.

PTFE main additives

As written before, virgin polytetrafluorethylene can be improved by the addition of different fillers. Most common are:

• Glass fibre. Increase wear resistance, pressure and assure a better thermal conductivity. Chemical resistance and dielectric properties are still very good (we call this material PTFE GF25);
• Carbon-graphite. Better lubricating effect, with a low friction coefficient. It assures a no static charging, good thermal conductivity and very good chemical resistance too (we call this material PTFE CG25);
• Bronze. Great wear behaviour, low cold flow, good thermal conductivity, high pressure resistance but lower chemical resistance (we call this material PTFE BR60);
• Carbon. Especially used and conductive filler. With carbon we obtain an electroconductive polytetrafluorethylene and we achieved higher pressure resistance and hardness, good sliding properties and wear behaviour, low surface and volume resistivity (we call this material PTFE ELS).

Modified PTFE (PTFE TFM)

Derived from standard PTFE, modified PTFE (which we call PTFE TFM) is a copolymer of tetrafluoroethylene and a small quantity of a per fluorinated modifier (perfluoro propyl vinyl ether, PPVE). The modifier content is less than 1%.

Modified Polytetrafluorethylene can be considered a second-generation PTFE. While retaining the exceptional properties of polytetrafluorethylene, it offers significantly improved properties:

• lower deformation under load (cold flow reduced by a factor of three);
• denser polymer structure;
• reduced permeation of chemicals and gases down to half of the standard PTFE value;
• smoother surfaces on machined parts;
• higher transparency;
• excellent weldability.

Most common brand names

PTFE is usually known as Teflon, the most famous brand name for this material. Polytetrafluorethylene is available in a wide range of shapes and dimensions. We actually purchase PTFE by the most important Italian producers.

Miscellaneous information

VERGIN PTFE is physiologically inert and it can be certified EU 10/2011 and FDA. And that’s not all, semi-finished materials can be certified USP Class VI too.

PTFE in few words.

Special properties:

• Service Temperature of between -200 °C and +260 °C (up to +300 °C for short periods);
• Almost universal chemical resistance;
• Virtually limitless UV and weather resistance;
• Antiadhesive behaviour;
• Outstanding sliding and frictional properties (no stick-slip effect);
• Good electrical and dielectric properties;
• Inherently flame-retardant in accordance with UL 94 V-0;
• Physiologically harmless;
• Suitable for food-contact materials.

Used in:

• Chemical industry;
• Oil & Gas;
• Pumps & Valves;
• Pharma & Medical.

Applications:

• Corrosion protection in the chemical industry;
• Insulating material for electronics and electrical engineering;
• Seals in vehicle fuel injection systems;
• Components of exhaust gas sensors in cars;
• Sealing and sliding elements in aircraft;
• Coatings for pistons, heating elements, and rollers, etc.;
• Construction of medical apparatus;
• Hygienically safe functional components in the food industry;
• Tubes for the chemical, pharmaceutical, and automotive industries;
• Large diameter seals for oil and gas extraction;
• Seals and sliding elements in wind turbines;
• Diaphragms in valves and pumps.