Design of effective surface contacts on polymer composites modified with multiwalled carbon nanotubes

In this article, we investigate the use of laser processing to create effective surface contacts on multi-wall carbon nanotube (MWCNT)/polyethylene composites. Due to the photothermal conversion effect induced by laser radiation, MWCNTs can enhance thermal destruction and removal of the polymer from the composite surface. The structure of pristine and laser modified composites is characterized by Raman spectroscopy, optical and scanning electron microscopy. It was found that in pristine composites only a small part of MWCNTs is located directly on the surface of the film, which is associated with the high work of polymer adhesion to the nanotube surface and the surface tension forces of the polymer matrix melt. Scanning electron microscopy (SEM) and Raman scattering demonstrate that in the surface contacts formed under the action of laser radiation, the polymer matrix is removed from the near-surface layer. The presence of MWCNTs with an unchanged structure and a small amount of amorphous carbon material was confirmed by Raman spectroscopy. The conductivity of pristine and modified composites was characterized by a series of current-voltage characteristic measurements with the through-plane 4-point probe. It was found that laser treatment of the composite surface leads to an increase in the measured volume conductivity by 1-2 orders of magnitude, depending on the content of MWCNTs. At the same time, the removal of the near-surface layer of the polymer by laser treatment makes it possible to reduce the contribution of the contact resistance to the resistance of the composite measured by 2-point probe from 55-77 to 0.18-5.3% for composites with an MWCNT content of 2.5-4 wt%.