Plastic Materials

United Material Piston Rings:  manufactures PTFE piston rings for oil-free compressors for many years. The demand for seals suitable for oil-free applications has grown considerably in recent years. This development has largely been driven by increased awareness of environmental concerns, more strigent regulations and the constant need to achieve further cost reductions.

We have developed a system range of PTFE special compounds enabling us to offer the product even for extreme application conditions. 


Product Information:


United Material

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Product life reach 6000-12000 hours, which is 4-12 times longer than the similar kind of piston rings.



Straight Joint

Piston rings with the straight joints are used for sealing pressure differences above 15 bars. With this gap, leakage is slightly higher than with piston rings that have a scarf joint. Due to the high compressor speeds (rpm) typically achieved today, the loss of gas has minor impact on compressor performance. The amount of gas leakage is negligible.

Scarf Joint

Piston rings with scarf joints are used for sealing pressure differences above 15 bar. During the run-in period the sealing effect (tightness) of scarf joints is slightly better than that of piston rings with a straight joint.

Overlapped Joint

The overlapped joint achieves a favorable sealing effect. For this reason, it is primarily used for sealing gases with a specific light weight. Due to the occurrence of bending stress and the resulting risk of breakage in the overlapping areas, piston rings with overlapped joints should only be used in compressors operating with pressure differences of a maximum of 15 bar.

Gas-tight Joint

Our gas-tight piston rings achieve the best sealing effect. The special design of the joint reduces leakage to a minimum. As with the overlapping joint the level of differential pressure is limited to a maximum of 15 bar. With regard to assembly please note that the piston ring achieves it’s good sealing effect only in one direction of pressure.

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