Influence of implantation of heavy metallic ions on the mechanical properties of two polymers, polystyrene and polyethyl
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Influence of implantation of heavy metallic ions on the mechanical properties of two polymers, polystyrene and polyethylene terephthalate Michael V. Swain CSIRO Division of Applied Physics, Lindfield, New South Wales 2070, and Department of Mechanical and Mechatronic Engineering, University of Sydney, New South Wales 2006, Australia
Anthony J. Perry, James R. Treglio, and Alex Elkind ISM Technologies Inc., 9965 Carroll Canyon Road, San Diego, California 92131
J. Derek Demaree U.S. Army Research Laboratory, Materials Directorate, Watertown, Massachusetts 02172-0001 (Received 29 April 1996; accepted 19 February 1997)
Ion implantation of polyethylene terephthalate (PET) and polystyrene (PS) with various high energy metallic ions at 70 kV and a dose of 3 3 1016 ionsycm2 has been made. Measurements of the mechanical properties of the polymers before and after implantation have been made with an ultra microindentation system using both pointed and a small (2 mm) radius spherical-tipped indenter. The surface regions were also investigated by atomic force microscopy (AFM) and Rutherford backscattering (RBS). Significant differences have been observed between the Ti–B dual-implanted surfaces and those of the Au and W implanted surfaces. For both the PET and PS, the resistance to indenter penetration at very low loads was much greater for the Ti–B dual-implanted surfaces. The estimated maximum hardness and modulus of the implanted materials were 0.3 and 8 GPa for the PET material and 1.4 and 16 GPa for the PS material. The results obtained with the spherical indenter show a gradual decline in effective modulus of the surface with penetration depth, whereas the hardness or contact pressure goes through a maximum before declining asymptotically to the bulk values. The values of hardness estimated for the spherical-tipped indenter are somewhat more conservative than the optimistic estimates with the Berkovich indenter. The improved increase in hardness for the Ti–B dual-implanted PET material scales with the RBS measured increased depth of implantation.
I. INTRODUCTION
Over the past decade there have been many reports of the influence of ion implantation on the properties of polymers.1–11 These authors have reported on the influence of ion implantation on the electrostatic surface resistivity of PVC1 and PET,2 optical and shrinkage effects,3 as well as resistance to cutting,7 hardness and wear resistance.4–11 The latter authors have made a systematic study and shown that the high energy implantation with virtually any species imparts improved surface wear properties to the polymer. Lee and colleagues4–6 and Pivin10,11 have undertaken more detailed studies on this topic and have made precision measurements of the force-displacement response to determine the mechanical properties of these very thin surface modified regions of many polymers. The former authors have also made claims that the hardness of the implanted polymer exceeds that of steel. J. Mater. Res., Vol. 12, No. 7, Jul
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