What material is used for the solid lubricant for underwater oilless bearings?

In the case of underwater oilless bearings, water pollution and color change prevention are the most important considerations. So, for this purpose, solid lubricants containing Mos2 or Carbon cannot be used, and general impregnation oils cannot be used. In the case of grease, it is necessary to use special waterproof grease or hydrophobic (Hydrophobic) grease, and the performance may be deteriorated during prolonged contact.

Therefore submersible oilless bearings have excellent heat resistance and corrosion resistance and friction is used for the solid lubricant with resin material of PTFE or Teflon series, and one which utilizes bearings designed to form a number of semi-dry friction manner and differentiation lubricant film must .

Submersible oil-less bearing solid lubricant is PTFE (Polytetrafluoroethylene) The production of a material.

Polytetrafluoroethylene has excellent chemical resistance, has a low coefficient of friction (0.04 ~ 0.08), and is a stable material that does not change its properties even at high temperatures (-260℃ ~ +260℃).

The table above summarizes the properties of PTFE, and PTFE is used according to the manufacturing method. 

There are two types: Suspension (Gel-Type) and Dispersion (Solid-Type) .

Suspension PTFE: Good frictional properties, but difficult to manufacture with lubricants (soft and hard) (it is atypical and is used as a grease additive).

Dispersion PTFE: It is advantageous for manufacturing lubricant-driven furnaces, but its frictional properties are somewhat inadequate compared to suspension PTFE.

In the case of pure PTFE, a load of about 40 MPa can withstand high loads, but deformation tends to occur when an overload occurs.

To this end, the design load including the safety factor is about 60% and a load of about 14 MPa is applied.

Long-chain polymer materials such as polyethylene, polypropylenes, and nylon are good materials that can be used as solid lubricants to form thin films because they have sufficiently low shear strength.

Among them, PTFE and Teflon have relatively low adhesion on the contact surface, so they are good in dry friction conditions (wet friction, such as underwater, does not easily adhere!).

So, PTFE material can be found in plastic bearings mainly used in computer equipment and printers in addition to underwater bearings.

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