Effects of argon ion sputtering on the surface of graphene/polyethylene composites

13 Figures, 1 Table.-- © 2019. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/Argon ion sputtering at various energies in the range of 500–5000 eV is performed on polymer composites of ultra-high molecular weight polyethylene (UHMWPE) with 4.6 wt% graphene nanoplatelets (GNPs). X-ray photoelectron spectroscopy (XPS) shows that irradiation above 3000 eV causes an abrupt transition from tetrahedral sp3 into planar sp2 carbon in the blank polyethylene surface. This graphitization process, as well as the formation of certain oxygen groups after the subsequent exposure to air, is delayed by graphene in the composites. Besides, both XPS and Raman spectroscopy indicate that a part of the sp2 graphene network is transformed into sp3 carbon defects by irradiation. Surface hardness and Young's modulus increase by 30–100% in blank polyethylene and the composites upon irradiation. The surface electrical resistance of polyethylene decreases from 1015 to 108 Ω by sputtering at 5000 eV. Composites that are consolidated at low temperature (175 °C) experience a transition from insulating (1015 Ω) to conducting (104 Ω) in a narrow range of Ar+ sputtering energies, while for a high consolidation temperature (240 °C) the transition is not observed. This research provides information on the induced interaction mechanisms between graphene and a polymer matrix upon ion beam irradiation.This work has been funded by the Spanish Ministry of Science and the European Regional Development Fund (ENE 2016-79282-C5-1-R), and the Government of Aragon together with the European Social Fund (DGA ESF T48-17R and T03-17R).Peer reviewe