Effects of metal-ion implantation on wear properties of polypropylene

Abstract

Polypropylene was implanted with 100 keV titanium and silver ions to fluences of 1, 10 and 50×10¹⁹ ions m⁻² using a vacuum arc metal-ion source. The implanted specimens were tested for sliding reciprocating wear properties using a nylon counterface, 1 N normal load, 3 mm stroke length and 10000 sliding cycles. The results of the wear tests showed that there was a dramatic improvement in wear properties for the 50×10¹⁹ ions m⁻² titanium-implanted specimen, to the point that no wear damage was visibly evident after 10000 cycles. A similar wear improvement was not obtained for the lower fluences for titanium implantation or for the silver-implanted specimens. The improvement in wear properties was related to the mechanisms of linear energy transfer from the incident ions to the polypropylene substrate, and consequent effects on cross-linking, which is responsible for changes in properties. The linear energy transfer was quantified using Monte Carlo calculations. In addition, friction coefficient values were also correlated with the wear test results. The significance of high fluences for wear improvements by ion implantation was demonstrated in this study. The investigation showed that metal-ion implantation can be effective in significantly improving wear properties of polymers with a judicious choice of ion type and ion fluence.