Tribological Properties of Polypropylene Composites with Carbon Nanotubes and Sepiolite

Abstract

Carbon nanotubes (CNTs) and sepiolite (SEP) were modified in order to improve their compatibility with the polypropylene (PP) matrix. Carboxylic groups were introduced into the CNTs through an oxidative treatment and aliphatic chains were incorporated on SEP by ion exchange of a cationic surfactant. Maleic anhydride grafted polypropylene (PPgMA) was mixed with neat PP to introduce polar groups into the polymer matrix. Composites including modified and non-modified fillers were prepared by melt extrusion. Dispersion and interaction of the CNTs with the PP and PPgMA matrices were evaluated by Raman spectroscopy while a focused ion beam/scanning electron microscopy (FIB/SEM) was used for SEP containing composites. Scratch resistance, microhardness, dynamic friction and wear were determined. Raman spectroscopy shows that the introduction of polar groups into PP matrices has a positive effect on the dispersion of modified CNTs. FIB/SEM results show that the modification of SEP improves its dispersion in the polypropylene matrix; filler clusters found in the PPgMA matrix are much times smaller than those in the neat PP. Despite of SEP agglomerates in the composites, a good interaction between both phases is seen; SEP particles are fully coated and embedded inside the PP matrix. The 'lack of cooperation' between unmodified PP and its fillers results in nanocomposites with larger residual depths; by contrast, PPgMA does 'cooperate' with its fillers so that the nanocomposites in scratch resistance testing have smaller residual depths R(h) than the neat PPgMA. Addition of the fillers to PPgMA also increases the hardness. As for wear rates, some our fillers provide higher and some lower wear rates than PP.

Evaluation of nanocomposites containing graphene nanoplatelets: Mechanical properties and combustion behavior

“…Better results can be seen with the use of PP‐ g ‐MA as a compatibilizer . In fact, PP‐ g ‐MA is the most convenient compatibilizer to use since it changes the internal structure and morphology of the GNPs‐based nanocomposite, as well as enhances the filler–matrix interaction .…”

“…GNPs are considered the most promising fillers for improving the intrinsic properties of polymers, giving rise to a novel class of polymeric nanocomposites that could be used in different application fields, including electronics, aerospace, automotive, and green energy industry .…”

“…Among them, PP‐grafted‐maleic anhydride (PP‐ g ‐MA) is the most convenient compatibilizer to be used. However, little effort is devoted to investigating the PP/GNPs nanocomposites in the presence of a compatibilizer .…”

Facile synthesis of thermally reduced graphene oxide-sepiolite nanohybrid via intercalation and thermal reduction method

“…Due to its large textural properties and surface activity, it can also act as a structure directing agent for the preparation of conducting carbon materials from the organic precursors (Darder and Ruiz-Hitzky, 2005;Avile's et al, 2007Avile's et al, , 2010Hitzky et al, 2011). Sepiolite has been self-assembled with metal oxides, carbon nanotubes, graphene nanomaterials via intercalation as well hydrophobic interaction mechanisms (Suarez et al, 2009;Garcı'a et al, 2013;Orozco et al, 2014). In recent years, graphene based hybrid materials have received much research attention due to tailored properties and potential applications in various fields (Chang and Wu, 2013;Li et al, 2014a, b).…”

Investigation of carbon nanotube-containing film on silicon substrates and its tribological behavior

“…Because of these unique properties, CNTs have been applied as anti-friction and wear-resisting materials in the field of tribology, such as fillers in polymers [13,14] and metals [15][16][17], additives in various liquid lubricant media [18], etc. If CNTs can be coated directly onto a surface to form CNT-containing film in pure form, they cannot to provide higher load support but to improve lubricating performance for the film.…”