ORIGINAL PAPER Nanofibrillated cellulose/carboxymethyl cellulose composite with improved wet strength Nikolaos Pahimanolis • Arto Salminen • Paavo A. Penttila ¨ • Juuso T. Korhonen • Leena-Sisko Johansson • Janne Ruokolainen • Ritva Serimaa • Jukka Seppa ¨la ¨ Received: 23 November 2012 / Accepted: 3 April 2013 / Published online: 11 April 2013 Ó Springer Science+Business Media Dordrecht 2013 Abstract In this paper, nanofibrillated cellulose/ carboxymethyl cellulose (CMC) composite films were prepared using tape casting. The obtained transparent films showed shear induced partial alignment of fibrils along the casting direction, resulting in birefringence in cross polarized light. The carboxyl groups of CMC could be further utilized to create ionic crosslinking by treatment with glycidyl trimethyl ammonium chloride (GTMA). The GTMA treated composite films had improved mechanical properties both in wet and dry state. The chemical composition and morphologies of composites were analyzed with X-ray photoelectron spectroscopy, elemental analysis, scanning electron microscopy and wide-angle X-ray scattering. Keywords Nanofibrillated cellulose Á Nanocellulose Á Carboxymethyl cellulose Á Ionic crosslinking Á Orientation Á Tape casting Introduction There is an increasing interest to utilize the potential of natural fibers due to their abundant availability and biodegradability. Nanofibrillated or microfibrillated cellulose can be produced by mechanical disintegra- tion of pulp fibers though a process first described by Turbak et al. (1983) and Herrick et al. (1983) and the process was further developed with oxidation or enzymatic pretreatments (Saito et al. 2006; Pa ¨a ¨kko ¨ et al. 2007). Characteristics of the obtained fibrils are a small diameter and high aspect ratio and because of its high strength, it is an interesting material as a reinforcing element in polymer composites for various applications. However, nanofibrillated cellulose (NFC) is hydrophilic and obtained as a dilute water suspension usually below 2 wt% of solid content, having a flocculated, entangled network structure (Saarikoski et al. 2012; Karppinen et al. 2012; Plackett and Siro ´ 2010) This makes it challenging as a composite material. Polymer composites of NFC have been produced via solvent-exchange procedures or by chemical modification of the surface of NFC fibrils to obtain better compatibility with polymers (Plackett N. Pahimanolis Á A. Salminen Á J. Seppa ¨la ¨(&) Polymer Technology, Department of Biotechnology and Chemical Technology, Aalto University School of Chemical Technology, P.O. Box 16100, 00076 Aalto, Finland e-mail: jukka.seppala@aalto.fi P. A. Penttila ¨ Á R. Serimaa Department of Physics, University of Helsinki, P.O. Box 64, 00014 Helsinki, Finland J. T. Korhonen Á J. Ruokolainen Molecular Materials, Department of Applied Physics, Aalto University School of Science, P.O. Box 15100, 00076 Aalto, Finland L.-S. Johansson Department of Forest Products Technology, P.O. Box 16100, 00076 Aalto, Finland 123 Cellulose (2013) 20:1459–1468 DOI 10.1007/s10570-013-9923-5