Improved wear properties of high energy ion-implanted polycarbonate

Polycarbonate (Lexan^TM) (PC) was implanted with 2 MeV B⁺ and O⁺ ions separately to fluences of 5 × 10¹⁷, 1 × 10¹⁸, and 5 × 10¹⁸ ions/m², and characterized for changes in surface hardness and tribological properties. Results of tests showed that hardness values of all implanted specimens increased over those of the unirradiated material, and the O⁺ implantation was more effective in improving hardness for a given fluence than the B⁺ implantation. Reciprocating sliding wear tests using a nylon ball counterface yielded significant improvements for all implanted specimens except for the 5 × 10¹⁷ ions/m² B⁺-implanted PC. Wear tests conducted with a 52100 steel ball yielded significant improvements for the highest fluence of 5 × 10¹⁸ ions/m² for both ions, but not for the two lower fluences. The improvements in properties were related to Linear Energy Transfer (LET) mechanisms, where it was shown that the O⁺ implantation caused greater ionization, thereby greater cross-linking at the surface corresponding to much better improvements in properties. The results were also compared with a previous study on PC using 200 keV B⁺ ions. The present study indicates that high energy ion irradiation produces thicker, more cross-linked, harder, and more wear-resistant surfaces on polymers and thereby improves properties to a greater extent and more efficiently than lower energy ion implantation.