Abstract
An investigation has been made of the static friction of various resin-bonded fibre materials lubricated by water in a thrust-bearing rig.
The static friction of water-lubricated phenolic resin-bonded asbestos materials mated with steel is initially low, μ = 013–0·3. This low friction is consistent with the composition of the bearing surfaces as it lies between that of asbestos and that of resin, on clean steel.
On running-in, the static friction of these materials increases substantially to μ = 0·3–0·6. Evidence has been found that this is due to the formation of a surface layer on both the mating surfaces causing adhesion. It is concluded that the layer is thermoplastic in nature. Because of this behaviour static friction measurements in which the mating surfaces are not run-in give an unrealistically low value for the static friction.
The suggestion that water is held by surface fibres and hence provides boundary lubrication is not borne out by the present results.
Under the test conditions employed the static friction of phenolic resin-bonded materials in which polythene and graphite had been incorporated was not lower than that of the parent materials. This was probably because the friction of polythene itself can be high due to its adhesion to the mating steel, and it is evidently difficult to add sufficient graphite to reduce the friction and yet maintain the physical strength.
The static friction of silicone resin-bonded asbestos and polyester resin-bonded cellulosic materials can also be high, probably for the same reason that the phenolic resin materials develop a high friction.
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