THE NATURE OF POLYMER FRICTION.

Abstract

THE SLIDING FRICTION BETWEEN A SOLID POLYMER AND ANOTHER SOLID (POLYMER, METAL, GLASS) USUALLY IS DETERMINED BY THE WORK OF DEFORMATION OF THE POLYMER(S).THE RATIO F/N OF FRICTIONAL FORCE TO NORMAL LOAD COMMONLY DECREASED FOR POLYMERS WHEN N INCREASES BECAUSE F IS PROPORTIONAL TO M/SUP MP/LUS/SUP N/ AND M PLUS N + 1; M AND N/SUB M/ ARE DEFINED BY THE EXPRESSIONS W EQUALS K/SUB 1/N/SUP M/ AND D EQUALS K/SUB 2/N/SUP N/; W AND D ARE THE WIDTH AND THE DEPTH OF THE DISTURBED MATERIAL; K/SUB 1/ AND K/SUB 2/ ARE PROPORTIONALITY CONSTANTS.FRICTION IN REPRODUCIBLE SLIDING IS NEVER CAUSED BY ADHESION.THE ABSENCE OF ADHESION IS PROVED BY THE EASE OF NORMAL SEPARATION OF SLIDER AND SUPPORT; AND THE CAUSE OF THIS ABSENCE IS THE PRESENCE OF WEAK BOUNDARY LAYERS (AIR, MOISTURE, ETC.) BETWEEN THE TWO.WHEN THESE LAYERS ARE ELIMINATED, ADHERENCE OF SLIDER TO SUPPORT OCCURS AND NO USUAL SLIDING IS POSSIBLE.ATTEMPTS TO CORRELATE F WITH THE TRUE AREA S OF CONTACT ARE MISLEADING BECAUSE WORK MUST BE PERFORMED TO ACHIEVE THIS S.THE COMMON DETERMINATIONS OF S ARE UNSATISFACTORY.THEORETICAL AND EXPERIMENTAL DETERWINATIONS OF THE WORK DONE DURING FRICTIONAL DEFORMATION OF VISCOELASTIC POLYMERS IS NEEDED TO ACCOUNT FOR THE OBSERVED FRICTION.(A.)