Effect of ion implant dose on the mechanical properties of polyethersulfone films
- PDF / 604,644 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 51 Downloads / 127 Views
Yongquiang Wang Institute of Technology Characterization Facility, University of Minnesota, 100 Union St. S.E., Minneapolis, Minnesota 55455
William W. Gerberich Department of Chemical Engineering and Materials Science, University of Minnesota, 421 Washington Ave. S.E., Minneapolis, Minnesota 55455 (Received 4 May 2001; accepted 3 October 2001)
Films of poly(ether sulfone) have been implanted with 50-keV As+ in the dose range of 1015 to 1017 ions/cm2. Nanoindentation tests were then conducted on these films using a conical diamond tip with a 90° included angle, applying loads from 10 N to 2 mN. The modulus and hardness were evaluated from the load–displacement data using the elastic unloading [J. Mater. Res. 7, 1564 (1992)] and the elastic–plastic unloading [J. Mater. Res. 13, 421 (1998)] models. The latter approach gave more reliable values for the mechanical properties since it is not as sensitive to creep-in effects. The implanted film showed as much as a twofold increase in hardness compared to the unimplanted polymer. However, the films with the highest dose did not exhibit the maximum values for the mechanical properties. Hardness and modulus values increased with increasing implantation dose up to 1 × 1017 ions/cm2 but dropped at higher doses, presumably due to a combination of sputtering of material and surface roughening. The dose dependence of the mechanical properties is observed to have the same trend as are reported for the electrical properties.
I. INTRODUCTION
Numerous studies have been made on the effects of ion implantation on both the electronic and mechanical properties of polymer films.1–10 It has generally been observed that ion implantation enhances the conductivity of polymers that are normally insulating, and this could lead to novel applications that require materials which are lightweight and capable of forming intricate shapes. At the same time, ion implantation alters the mechanical properties of the polymer surface. Enhancement in hardness, modulus, adhesion, and wear resistance has been reported,3–9 and some authors have even claimed that the implanted polymers were harder than steel. These effects are intimately linked to the microstructural reorganization of the surface. Ion bombardment and implantation on polymers cause scission of chemical bonds and cross-linking of chains, as well as formation of radicals and precipitate particles due to the interaction of the implanted ions to other species in the polymer. In addition, loss of gaseous molecules (such as H2 and Cl2) leads to enrichment of specific elements (usually C) on the surface. 3628
http://journals.cambridge.org
J. Mater. Res., Vol. 16, No. 12, Dec 2001 Downloaded: 04 Apr 2015
Poly(ether sulfone) (abbreviated as PES, structure in Fig. 1) is known to have high thermal stability, strong mechanical, and relatively low dielectric constant properties.1,11,12 The sulfur to carbon linkages in the polymer backbone are stabilized through conjugation, which imparts chemical resistance to the polymer. The behavior of high-perfo
Data Loading...
