Modifications of polypropylene surface properties by He+ ion implantation

A polypropylene (PP) modified by ethylene–propylene rubber (EPR) was treated in vacuo by α particles (with an energy of 400 keV) with fluences that varied from 1011 to 1016 He+ cm−2. Samples were investigated with attenuated total reflection Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, contact-angle measurements, differential scanning calorimetry, swelling, nanoindentation, and friction techniques. After treatment, new chemical groups (carbonyl and vinyl bonds) appeared at the PP/EPR surface. These chemical modifications led to changes in the surface free energy of PP/EPR. Irradiation also modified the PP/EPR structure because crosslinking occurred after treatment for fluences above or equal to 5 × 1014 He+ cm−2. Moreover, the PP melting temperature and enthalpy were greatly decreased for fluences above or equal to 1014 He+ cm−2. The surface mechanical properties were also changed after treatment. Indeed, the friction coefficient decreased, whereas the hardness and Young's modulus drastically increased, after irradiation at higher fluences. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1183–1191, 2003