Valve Seat Material

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Valve Seat Material

Virgin PTFE

Characteristic

Polytetrafluoroethylene or PTFE is the commonly used versatile, high-performance fluoropolymer made up of carbon and fluorine atoms.

Apart from being used in the kitchen, PTFE is used as a cost-effective solution for industries ranging from oil & gas, chemical processing, industrial to electrical/electronic and construction sector, etc. of the common applications of this polymer is non-stick coating in kitchen cookware (pans, baking trays etc.), hence, you can easily find this in your kitchen.

Properties

PTFE's melting point is around 327°C, and pure PTFE is almost totally chemically inert, highly insoluble in most solvents or chemicals, and thermally stable enough to be used between -200 degrees C and +260 degrees C without degrading.

Strengths

Highly flexible

Chemical resistant

Non-stick and electrically resistantThermal resistant

Modified PTFE

Characteristic

Lower deformation under load (cold flow reduced by a factor of three)Stronger and more versatile than regular PTFE

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 weld ability

Properties

TFM, known as PTFE-TFM, is polytetrafluoroethylene with perfluoropropylvinylether as an additional modifier, giving a denser material which is stiffer, also creep resistant like PFA, and weldable.

Strengths

FDA certified

Better creep performance

Good electrical and mechanical properties

Lower permeability

Glass Fiber filled PTFE

Characteristic

It improves cold flow resistance and wear resistance, widely used for piston ring., bearing, like gaskets etc.

Glass fiber is the most commonly used filler in PTFE as it offers much improved compression and wear properties

The material may also be inert gas sintered to further improve creep properties and reduce porosity and gas permeability but please be noted that would be a consequent loss of tensile properties.

Properties

Glass Filled PTFE is reinforced with glass fibers with the percentage varying between 5% and 40% depending on the needs of the application. As the filler percentage increases so does the properties the filler offers (increased compressive strength, lower deformation under load) but conversely the coefficient of friction properties of the material increases over that of virgin PTFE.

Strengths

Wear resistant

Improved hardness

Lower thermal expansion

Lower deformation under load

Non-conductive

Weaknesses

Higher coefficient of friction.

Abrasive filler unsuitable for some applications.

Resistance to gas permeation is reduced.

It will be damaged by hydrogen fluoride and strong alkalines.

Graphite Filled PTFE

Characteristic

Highly effective in sealing various types of chemicals. Graphite lowers the coefficient of friction and Graphite filled PTFE has excellent self-lubricating properties.

Properties

The percentages used vary between 5 and 15%. Graphite lowers the coefficient of friction and is, therefore, often added to other types of filled PTFE for improving this property. It improves the deformation under load, strength and, to a minor degree, the wear properties.

Strengths

Cold flow resistance

Low starting friction

Low coefficient of friction

Chemically resistant

Wear & Tear resistance

Excellent engine efficiency

Weaknesses

Not resistant to halogenides, elemental fluorine, CF3, molten alkali metal

Bronze filled PTFE

Characteristic

The addition of Bronze to PTFE gives better dimensional stability and lowers creep, cold flow and wear resistance. It increases hardness and compressive strength whilst also increasing thermal and electrical conductivity.

Properties

Reinforced with bronze powder with the percentage varying between 40% and 60%, resulting in a very hard wearing material.

Strengths

Extremely hard wearing material

Very heavy-high specific gravity

Electrically conductive

The best wear properties of any filled PTFE

Great deformation strengths

Good thermal conductivity

Weaknesses

Not suitable for electrical applications

Poor chemical resistance than other grades of PTFE

Carbon Fiber filled PTFE

Characteristic

It improves mechanical characteristics, such as wear resistance, load resistance characteristics and flexuaral strength. It is often the best choice in automotive applications such as shock absorbers and water pumps. It is an excellent material for use in piston rings, bearings and thrust washers.

Properties

Carbon Fiber lowers creep and increases flex and compressive modulus. It raises hardness properties and exhibits wear characteristics in water applications. A 15% fill is typically called out in certain AMS specifications (Aerospace Material Specifications), however customer specific fill percentages are available upon request.

Strengths

Improved Compression and Wear Resistance

Excellent Chemical Resistance

High Strength Properties

PEEK

Characteristic

PEEK offers chemical and hydrolysis resistance similar to PPS, but can operate at higher temperatures. It can also be used in hot water or steam without permanent loss in physical properties.

Properties

PEEK offers good wear resistance and can be used continuously to 480°F (250°C). For hostile environments, PEEK is a high strength alternative to fluoropolymers and carries a V-O flammability rating and exhibits very low smoke and toxic gas emission when exposed to flame.

Strengths

Excellent mechanical and chemical resistance

Thermal properties and high-temperature tenacity

Low moisture absorption

Good wear and abrasion resistance

Long service life

Excellent heat distortion properties

Low coefficient of friction

Good radiation resistance

Low flammability

Weaknesses

Higher price

PEEK is attacked by halogens and strong acids as well as some halogenated compounds and aliphatic hydrocarbons at high temperatures. It dissolves completely in concentrated sulfuric acid at room temperature.

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