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SF-2 Boundary lubricating Bushing

SF-2 material is a three-layer composite self-lubricating material made of polytetrafluoroethylene modified polyoxymethylene plastic as the surface layer. It is a benign boundary lubricating material, making it particularly suitable for bearings, thrust pads, sliders, ball seats, and other friction parts that are not easily lubricated by fluid dynamics due to high load and low-speed rotational motion, swinging motion, and frequent opening and closing under load. SF-2 can fully utilize trace amounts of lubricating grease and can be maintained for a long time without refueling under boundary lubrication conditions. Under completely oil-free lubrication conditions, the friction performance and allowable PV value of SF-2 are relatively low, so oil storage pits are usually rolled out on the plastic surface and lithium based lubricating grease or silicone grease is applied during assembly.

Golden statue picture Physical and mechanical properties Wear resistance Factors affecting lifespan

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Performance index		Data
Maximum bearing pressure P	Static load	140N/mm²
Maximum bearing pressure P	Dynamic	70N/mm²
Maximum bearing pressure P	Swing	60N/mm²
Maximum linear speed V	Grease	2.5m/s
Maximum PV value	Grease	2.8N/mm²· m/s

Performance index		Data
Coefficient of friction μ	Grease	0.06~0.12
Matching axis	Hardness	>270 HB
Matching axis	Roughness	Ra=0.4~1.25
Operation temperature		-40~+120℃
Thermal conductivity		52W/(m·k)
Thermal expansion coefficient (axial)		11×10^-6K^-1

Chemical properties

The surface polymer of SF-2 is resistant to chemical corrosion, so its corrosion resistance mainly depends on the steel back and the outer electroplating layer. Copper or tin plating on the surface of the steel back can effectively prevent atmospheric corrosion; If working in corrosive media, the steel back can be galvanized, etc.

Wear resistance

The wear characteristics of SF-2 under grease lubrication conditions are shown in the following figure: its "running in" wear rate is very low; As can be seen from the line segment in the figure, when the grease applied during assembly is consumed to a certain extent, its wear rate gradually increases, as shown by dashed line 1; If refueling is done again before the wear rate increases, the wear rate will still remain stable; When the refueling interval is appropriate, the service life of the material can be greatly extended. The refueling interval depends on the accumulated wear and tear.

When lubricating with grease: If the ambient temperature is below 80 ℃, it is recommended to use lithium soap based grease; If the ambient temperature is above 80 ℃, it is recommended to use silicone oil based grease; Oils and fats containing EP additives are not recommended.

1) The impact of PV value
PV value is an effective indicator for determining the wear life of SF-2. If an extension of lifespan is required, the PV value must be reduced.

2) The impact of environmental temperature
When the ambient temperature exceeds 40 ℃, the performance of SF-2 significantly decreases, and the higher the temperature, the shorter its relative lifespan.

3) The influence of roughness
When the dual surface roughness Ra is within the range of 0.4~0.63, the service life of SF-2 bearings can be significantly improved.