Effect of Air-Plasma Pre-treatment of Si Substrate on Adhesion Strength and Tribological Properties of a UHMWPE Film

Ultra High Molecular Weight Polyethylene (UHMWPE) film is dip coated onto piranha and air-plasma treated silicon substrates, to study the effect of surface pre-treatment on the adhesion strength and the tribological properties of the film. After the pre-treatment, water contact angle measurements were conducted and the surface free energy of the Si substrate was calculated. It is observed that the air-plasma pre-treatment reduced the water contact angle (4.3 degrees) considerably when compared to that of the piranha pre-treatment (21.3 degrees), which resulted in an increase of the surface free energy of the Si substrate. Scratch tests were conducted for studying the adhesion property of UHMWPE films coated onto Si substrate. It was found that the plasma pre-treatment enhanced adhesion between the UHMWPE film and the Si substrate by more than two times when compared to the piranha pre-treatment. Wear tests were conducted to study the effects of pre-treatments on the tribological properties of the UHMWPE film. UHMWPE film coated onto plasma pre-treated Si showed a wear life of about 50 000 cycles (25 times higher) as compared to that of 2000 cycles when it was coated onto piranha pre-treated Si, tested at a normal load of 1 N and a rotational speed of 200 rpm. (C) Koninklijke Brill NV, Leiden, 2010