Material properties Enhancing the mechanical performance of polymer based nanocomposites by plasma-modification of nanoparticles Roberto Scaffaro * , Andrea Maio University of Palermo, Dipartimento di Ingegneria Civile, Ambientale, Aerospaziale, dei Materiali, Viale delle Scienze, Ed. 6, 90128 Palermo, Italy article info Article history: Received 4 May 2012 Accepted 14 June 2012 Keywords: Carbon nanotubes Functionalization Nanocomposite Nanoclay Nanoparticle Plasma abstract The possibility of enhancing the mechanical performance of two different polymer-based nanocomposites using polyamide 6 (PA6) and poly[ethylene-co-(vinyl acetate)] (EVA) as matrices was investigated. The nanofillers used were, respectively, either carbon nano- tubes (CNTs) or an organically modified montmorillonite (Cloisite 15A), both previously modified by plasma treatment to introduce polar moieties. The nanofillers were fully characterized by Raman spectroscopy, XPS, FT-IR and XRD, demonstrating their effective modification with oxygenated groups. The nanocomposites were prepared by melt pro- cessing in order to obtain films and fibres. The mechanical tests carried out on the nanocomposites showed a remarkable increase of the elastic modulus when plasma- modified nanoparticles were used. The improvement of wettability and dispersion of the nanofillers in the polymer matrices, as confirmed by SEM observations, can be invoked to explain this feature. Ó 2012 Elsevier Ltd. All rights reserved. 1. Introduction Polymer nanocomposites have received significant attention during the last two decades, due to the possibility of obtaining high performance materials at low filler loading. This is possible because of the higher surface-to- volume ratio of nanofillers compared to that of traditional micro-scaled fillers [1,2] However, the dispersion and the adhesion of the nanofillers in the host polymers remain the key factors for obtaining improvement of the mechanical performance [1–4]. In fact, one of the main goals in the preparation of nano-scaled composites is to prevent the nanoparticles from agglomerating in clusters or bundles. This can be achieved by introducing specific surfactants or functional groups on the nanofiller surface in order to improve compatibility with the host polymer [2,4,5]. Clays and carbon nanotubes have been widely investi- gated and used as reinforcing agents for polymer matrices [1–8]. Clay-based nanocomposites can find applications in various areas, such as packaging and agriculture. They can dramatically enhance the mechanical performance and the barrier properties at filler loadings as low as 3-5 wt%, without significantly changing other important character- istics such as transparency or density. In order to enhance their compatibility with polymer matrices, clays are usually modified with organic compounds (e.g. quaternary ammonium salts) but, even in this case, the properties are often not significantly improved [1]. Carbon nanotubes (CNTs) have been found to be effec- tive reinforcing agents for several polymeric materials, beyond the capability to increase their electrical and thermal conductivity [4–6]. Similarly to clays, CNTs must be modified to improve their affinity with the matrix by including specific functional moieties (e.g. carboxyls, amine, hydroxyls ...) introduced by dedicated processes [4,5,8–10]. Despite several studies reporting on plasma modification of CNTs, to the best of our knowledge, no papers about plasma carboxylation of organoclays are available in the scientific literature. The aim of this work is the description of a rapid and solvent free method for modifying nanofillers to increase their compatibility with host polar polymers. In particular, the method aims to oxidize either carbon atoms of CNTs or those * Corresponding author. Fax: þ39 (0) 91 6567280. E-mail address: roberto.scaffaro@unipa.it (R. Scaffaro). Contents lists available at SciVerse ScienceDirect Polymer Testing journal homepage: www.elsevier.com/locate/polytest 0142-9418/$ – see front matter Ó 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.polymertesting.2012.06.006 Polymer Testing 31 (2012) 889–894