Macromolecular Nanotechnology Water transport in epoxy/MWCNT composites O. Starkova a,⇑ , S.T. Buschhorn b,1 , E. Mannov b , K. Schulte b , A. Aniskevich a a Institute of Polymer Mechanics, University of Latvia, Aizkraukles 23, LV-1006 Riga, Latvia b Institute of Polymers and Composites, Technische Universität Hamburg-Harburg, Denickestraße 15, D-21073 Hamburg, Germany article info Article history: Received 20 February 2013 Received in revised form 3 May 2013 Accepted 15 May 2013 Available online xxxx Keywords: Water diffusion Nanocomposite Free volume Swelling Hydrothermal ageing Thermomechanical analysis abstract Moisture and water uptake of epoxy/multi-wall carbon nanotube (MWCNT) composites was studied in a wide range of atmosphere relative humidity and temperatures. Addition of up to 1 wt.% of MWCNTs into the neat epoxy resulted to the twofold decrease of the dif- fusivity, while the levels of moisture/water uptake remained unchanged. The positive effect on the reduction of the diffusion coefficient diminishes with the increase of temper- ature. Differences in the water transport properties and plasticization ability of the neat polymer and its nanocomposites are explained by the free volume considerations and the polymer–water interactions, which are verified by the results of thermomechanical analysis. Water uptake by the nanocomposites resulted to a lower decrease of the storage modulus than that of the neat epoxy. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Epoxy resins are widely used as matrices for structural composite materials and adhesives in aerospace, automo- bile and civil industries due to their good thermal and mechanical properties and chemical resistance combined with satisfactory processing characteristics. In most appli- cations, such materials have the potential of being exposed to a humid environment and elevated temperature immer- sion and susceptible to water uptake. High tendency of epoxy matrices to moisture absorption from the environ- ment is one of the reliability concerns for composites. The absorbed moisture has deleterious effect on the physical and mechanical properties of epoxies and can, therefore, greatly compromise the performance of the epoxy-based component. By acting as an efficient plasti- cizer and increasing the polymer chain mobility, absorbed moisture diminishes the glass transition temperature (T g ), reduces the modulus and mechanical strength as well as induces swelling of the polymer [1–11]. The transport of water in epoxy systems and long-term performance of epoxy-based composites under environmental conditions are of great practical importance and are still under investigation. Incorporation of nano-structured carbon fillers, in par- ticular multi-wall carbon nanotubes (MWCNTs), into epoxy matrices may improve their effective properties and intro- duce ‘‘sensing functionality’’ by increasing the electrical conductive properties of the material. The combination of a nanotube-modified matrix together with conventional fibre-reinforcements provides a new generation of multi- functional materials with health monitoring capabilities [12–14]. The wider application of nanocomposites requires greater understanding of material performance and the ability to resist environmental effects during long-term use. The development of a comprehensive understanding of the mechanisms of ageing and environmental exposure related deterioration for purposes of prediction of service life and durability is of great importance to the further use of such systems. The nano-sized inclusions may influence the properties of environmentally-conditioned nanocomposites in two 0014-3057/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.eurpolymj.2013.05.010 ⇑ Corresponding author. Tel.: +371 67543120; fax: +371 67820467. E-mail address: olesja.starkova@pmi.lu.lv (O. Starkova). 1 Current address: Department of Aeronautics and Astronautics, Massachusetts Institute of Technology, 77 Massachusetts Ave., Cambridge, MA 02139, USA. European Polymer Journal xxx (2013) xxx–xxx Contents lists available at SciVerse ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj Please cite this article in press as: Starkova O et al. Water transport in epoxy/MWCNT composites. Eur Polym J (2013), http://dx.doi.org/ 10.1016/j.eurpolymj.2013.05.010 MACROMOLECULAR NANOTECHNOLOGY