Process of making a high molecular weight polyolefin part

Claim 1

A forging process for making a polyolefin part including an arcuate friction surface having improved creep and wear resistances comprising the steps of: (a) raising to the forging temperature a blank of high molecular weight polyolefin in which the blanks length/transverse dimension ratio is between approximately 0.6 and approximately 1.7, the forging temperature being in the temperature range from approximately 20° C. below the melting point Tf of said polyolefin and approximately 10° C. above said melting point Tf; (b) placing the blanks raised to the forging temperature in a forging mould which can be closed by a punch displaceable in translation in said mould in the lengthwise direction of the blank; (c) applying to the punch a pressure exceeding the yield stress of said polyolefin at said forging temperature and moving said punch to a final position for forging the blank in the mould with a reduction rate of 0.4 to 0.8 to provide a polyolefin part having an arcuate friction surface; (d) maintaining the punch in the final position for a period between approximately 90 and approximately 150 seconds; and (e) extracting the forged part from said mould.