EFFECT OF DIRECT FLUORINATION ON THE BONDING PROPERTY OF ULTRA-HIGH MOLECULAR WEIGHT POLYETHYLENE

The surface of ultra-high molecular weight polyethylene (UHMWPE) was modified by direct fluorination. The shear strength of laminar UHMWPE bonded with epoxy resin was enhanced up to 4.72 MPa, which showed that the adhesive ability of UHMWPE was obviously improved. At the same time, this kind of adhesive ability remained at room temperature beyond one month. According to the results of scanning electron microscopy (SEM), the surface topography of UHMWPE did not change much after fluorination, which indicated that the improvement of adhesive properties did not depend on the surface roughness. However, the polarity portion of UHMWPE surface apparently improved and the surface energy increased from 30 mN/m to 42.47 mN/m from contact angle measurements. In addition, X-ray photoelectron spectroscopy (XPS) and ATR-infrared spectroscopic analysis indicated that three kinds of polar functional groups, C-F-COOH and -OH, were introduced into the surface macromolecular chains in the form of covalent bonds, respectively. Thus, the bonding property of UHMWPE was improved owing to the change of surface chemical structure. Additionally, the mechanism of the formation of surface active groups by direct fluorination was proposed.