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The history of PTFE and Mehood`s advantage

  • author:mehoodUpload time:2016-4-4Tag:Browsing number:3471

Firstly,PTFE was used in military industry. Until the 1950 s, it was used in potted components .In the 70 s, some companies tried to use PTFE instead of rubber to make lip seal.
The first generation of PTFE seal was made by cutting and pressing PTFE bars,which was similar to rubber seal products in shape.But it failed soon.
The second generation was a stickup type seal invented by a Japanese company . It is like a layer of PTFE membrane sticked at the lips of the original rubber sealing to improve the performance of rubber seal .Since the complex paste process and high cost,but less effecient improved, it was not be widely used.
Later, the same company launched the third generation of seal. The procedure is to make PTFE material into trumpet-shaped film, then cover it with a leaf spring and a spiral spring.However it was not widely adopted due to the complex structure, compression strength and low life expectancy.
In 1975, a company in the United States called Mather made a wide lip structure of PTFE seals, known as the fourth generation. The process is to press PTFE material into round slice,later, make it into a trumpet-shaped, then insert it into the metal shell, meanwhile put a layer of rubber elastic .This new type structure of seal rubber seal is obviously different from traditional rubber seal.It not only has simple structure,but also doesn`t have spiral spring.Moreover,the contact surface with the shaft area is more wider with roughly 3 ~ 4 mm.Because PTFE could lubricate itself ,the lip is not easy to burn out.But the inside of this sealing lip is too sleek to seal.
Until the 80 s, a type dynamic seal with the lip wall engraved with the thread groove showed up,which is known as the five generation.The thread groove has a resistance power for the oil film on the surface of the shaft ,so as to prevent oil film leaking.The emergence of the fifth-generation products was a breakthrough for rotating lip seal .Currently the most popular lip seal is moulded thread and cutting thread.Through cutting thread on the contacting surface,it improves the coincidence with shaft,also enhances static sealing function.

PTFE oil seal is mainly applied to in engine, gearbox, air compressor, motor, pump, air conditioning, mixer, automatic precision machinery, robot, chemical processing equipment, pharmaceutical and food processing equipment,etc. It could substitute traditional rubber seal to meet high demand.

Through a large group of experiments, We have developed Bidirectional high-speed rotating seal,and obtained patent protection for this technique ,which extends the application of PTFE seal.

Performance Index

Traditional rubber seal

PTFE seal

Working Temperature

VITON:--15℃—+200℃,chemigum: -35℃—+100℃, not for extreamly cold weather

-100℃—+260℃ for all kinds of temperature

Corrosion resistance

Poor corrosion resistance:fluorine rubber has chemical reaction with ammonia

Suitable for all kinds of strong acid and alkali, salt and chemical fluid solvents such as acetone, ammonia, polyurethane etc.

Wear resisitance

Friction coefficient of Rubber is 0.2-0.4, the maximum linear velocity is about 15 m/s

Friction coefficient of PTFE is 0.02-0.04, for one over ten of the rubber, especially suitable for oil free or less oil working condition.Even after long downtime, it can immediately have low friction characteristics when restart machine.

Beat resistance

Beating resistance of rubber oil seal is less than 0.3 mm. Most of the high power engine use PTFE oil seal because of beating, also heavy-duty gearbox has to adopt double rubber oil seal to reduce failure with 0 km for the same reason.

Beating resistance of PTFE could be up to 0.85mm (diameter of shaft is 100mm)

Anti-memory ability

Relying on compression spring lip,rubber oil seal hold shaft. because of the spring uneven joint, eccentric wear on lip causes oil leakage.

PTFE has memory ability to shrink after drawing.Friction can produce heat to shrink lip constantly,which avoid gap between shaft and lips,also compensate for wear.

Contact surface

Lip contacts shaft in roop shap by the contraction force of spring,which could damage the shaft surface and shape grooves on it.

PTFE seal has a round contacting surface with 35mm wide.The lip and shaft contact naturally.