PTFE and its filling modification
The melting point of PTFE is 327 ℃, density is 2.18 ~ 2.3g/cm³, and shore hardness is D50 ~ D65, it has excellent chemical stability and self lubrication, it is the most widely used and the most used variety of fluorine plastics. It has excellent overall performance, for example: Resistant to high and low temperature, corrosion resistance, aging resistance, non adhesion, high insulation, high lubrication, no poison. However, PTFE has poor creep resistance, poor wear resistance, and large expansion coefficient. Therefore, it is usually necessary to overcome these defects by filling and modifying. Commonly used fillers are copper powder, carbon fiber, glass fiber, graphite, MoS2, polybenzoate, PEEK and so on, according to different conditions and uses can be filled with one or more of the material.
1. Pure PTFE products
Pure PTFE can add back-up ring, gaskets and other sealing, with high temperature, corrosion resistance, self-lubricating characteristics, But prone to creep and cause leakage under the load, it usually used in food, pharmaceutical and chemical industries.
2. PTFE filled copper powder modified products
Copper powder is the most commonly used filler for PTFE, and the PTFE sealing modified by filling copper powder has improved greatly in pressure resistance, wear resistance, thermal conductivity and creep resistance. For different performance requirements, different copper powder composition, particle size and filling ratio can be chosen to meet the actual demand. The product is usually used to make wear-resistant guide ring, wear-resistant tape, oil / cylinder seals and so on. The copper powder may be corroded under strong acid conditions and is therefore not recommended for use in strong acid conditions.
3. PTFE filled carbon fiber modified products
The PTFE seal modified by carbon fiber has greatly improved the pressure resistance, wear resistance, creep resistance and tensile strength, while improving the hardness of the products, and suitable for rotary sealing, usually used for the production of spring energy storage spring seal, automobile wave box oil ring and so on. Carbon fibers may be oxidized and decomposed in a strong acid environment, so they are not recommended for use in strong acid conditions.
4. PTFE filled glass fiber
It has greatly improved in pressure resistance, wear resistance, creep resistance and tensile strength after filled the glass fiber modified PTFE seal, while improving the hardness of the product, and suitable for rotary seal. Usually used for the production of gasket, spring energy storage spring seal, automobile wave box oil ring and so on. Glass fibers may decompose in alkaline conditions and are therefore not recommended for use in alkaline or water containing conditions.
5. PTFE filled graphite or MoS2 modified products
The main purpose of filling graphite or MoS2 modification is are to improve the pressure resistance and wear resistance, creep resistance and maintain the maximum low friction coefficient of PTFE and self lubrication characteristics. Usually filled with other fillers and can be individually filled, mainly used in the manufacture of spring energy storage spring seal, cylinder seal, self-lubricating shaft sleeve and so on. Apply to the condition that the coefficient of friction is low or inconvenient to add lubricant.
6. PTFE filled polybenzoate or PEEK modified products
It has greatly improved in pressure resistance, wear resistance, creep resistance after filled the polybenzoate or PEEK modified PTFE seal, and especially has greatly improved the toughness and hardness in a high temperature environment. Suitable for the static seal, the dynamic seal and the self lubrication piston ring of the compressor for long time working in the high temperature environment.