Tribological Properties of Ultra-Thin Functionalized Polyethylene Film Chemisorbed on Si with an Intermediate Benzophenone Layer
In this study, an ultra-thin (~20 nm) functionalized polyethylene (fPE) film is successfully attached to Si substrate via a reactive benzophenone (Ph2CO) layer. The presence of fPE promotes wear durability of Si/Ph2CO/fPE to 1,000 cycles compared with 100 cycles for Si/Ph2CO and nearly zero wear life for bare Si in a ball-on-disk (4-mm-diameter Si3N4 ball) wear test under 40 mN applied normal load and 500 rpm sliding speed. As an enhancement to the wear life, perfluoropolyether (PFPE) is applied as a top mobile lubricant layer coated onto Si/Ph2CO and Si/Ph2CO/fPE. A significant improvement in the wear durability is observed as Si/Ph2CO/PFPE fails at 250,000 cycles and Si/Ph2CO/fPE/PFPE does not fail until one million cycles. Si/Ph2CO/fPE/PFPE can withstand a minimum applied load of 150 mN at a sliding speed of 0.052 ms−1 without failure, providing a PV (pressure x velocity) limit of greater than 106.6 MPa ms−1.
KeywordsFunctionalized PE Boundary lubrication PFPE Polymer film Wear durability
This study is based on research work supported by the Singapore National Research Foundation under CRP Award no. NRF-CRP 2-2007-04. We would like to thank Dr. N. Satyanarayana for his valuable suggestions.
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