Industrial Crops and Products 36 (2012) 257–266 Contents lists available at SciVerse ScienceDirect Industrial Crops and Products journal homepage: www.elsevier.com/locate/indcrop Morphological and crystalline characterization of NaOH and NaOCl treated Agave americana L. fiber Asma El Oudiani Ben Sghaier ∗ , Yassin Chaabouni, Slah Msahli, Faouzi Sakli Research Unity of Textile URT, ISET KH, Ksar Hellal 5070, University of Monastir, Tunisia article info Article history: Received 25 May 2011 Received in revised form 14 September 2011 Accepted 22 September 2011 Available online 25 November 2011 Keywords: Agave fiber NaOCl treatment NaOH treatment Morphological characterization Chemical composition Crystallinity abstract This study investigates the effect of NaOH and NaOCl treatments on chemical composition, morphology and crystalline structure of Agave americana L. fibers. These fibers have been subjected to NaOCl and NaOH alkali treatments at different concentrations. The percentages of lignin and hemicellulose show a decrease with alkaline treatments which, in turn, induces a modification of both morphological and crystalline structures. Unit cell dimensions and crystallite size were more affected with NaOH treatment than NaOCl one. This may result from the mercerisation process which occurs with caustic soda treatment. The observed defibrillization on the treated fiber surface proves the dissolution of the non-cellulosic components present in the fiber cell wall by NaOH and NaOCl treatments. These morphological changes may improve the interaction between matrix and fiber in composites. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Lignocellulosic fibers, also called “plant” fibers, “natural” fibers or “vegetable” fibers, include bast fibers, leaf or hard fibers, seed, fruit, wood, cereal straw, and other grass fibers. These plant fibers have been one of the most attractive fillers for different types of polymers including rubbers as well as for ceramic matrices due to some of their unique characteristics unparalleled with any other reinforcing/filler materials. They include renewabil- ity, biodegradability, good availability, low cost and density, limited damage to the processing equipment, reduced health hazard and reasonable strength and stiffness. Consequently, there is an increased motivation in the use of plant fibers by different industrial sectors, like automotive, to replace glass fibers (Bledzki and Gassan, 1999; Saheb and Jog, 1999; Klemm et al., 2005; Avérous and Le Digabel, 2006; Rao and Rao, 2007). Besides, the use of natural fibers does not consume the energy required to melt and process fiberglass. Lignocellulosic fibers are constituted by three main components: hemicellulose, cellulose, and lignin which are known to present very complex structures (Yang et al., 2007). Cellulose, which is the main fraction of the fibers, is a semicrys- talline polysaccharide made up of d-glucosidic bonds. It forms a ∗ Corresponding author. Tel.: +216 22 930 867; fax: +216 73 475 163. E-mail address: asmaeloudiani@yahoo.fr (A.E.O. Ben Sghaier). skeletal frame that is surrounded and encrusted by the matrix sub- stances (hemicelluloses and lignin) (Reddy and Yang, 2005). A large amount of hydroxyl groups in cellulose (three in each repeating unit) gives hydrophilic properties to the natural fibers. Hemicel- lulose is strongly bound to the cellulose fibrils, presumably by hydrogen bonds. Hemicellulose polymers are branched, fully amor- phous and have a significantly lower molar mass than cellulose. Because of its open structure containing many hydroxyl and acetyl groups, hemicellulose is partly soluble in water and is hygroscopic. Lignins are amorphous, highly complex, mainly aromatic polymers with phenylpropane units, but have the lowest water sorption of the natural fiber components (Li et al., 2007). The fiber studied in this work was extracted from the leaves of Agave americana L. plant (Fig. 1). This fiber is one of the strongest and stiffest available natural fibers in Tunisia (El Oudiani et al., 2009) and therefore has great potential for use in composite materials. However, as a crop-based material, its properties depend on growing conditions, including growth duration and procedures involved to extract the fiber from the plant. Although acceptable mechanical properties have been obtained from distilled water extracted fiber (Chaâbouni, 2005), it may be best to further pro- cess the fibers for many applications to remove the lignin before inclusion into composites. Actually, chemical treatments of sur- face fibers have been reported to improve their wettability and to modify their microstructure, surface topography, surface chemical groups and tensile strength (Silva et al., 2000; Rout et al., 2001). 0926-6690/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.indcrop.2011.09.012