Preparation of cassava starch/montmorillonite composite film Piyaporn Kampeerapappun, Duangdao Aht-ong, Duanghathai Pentrakoon, Kawee Srikulkit * Department of Materials Science, Faculty of Science, Chulalongkorn University, Bangkok 10330, Thailand Received 25 June 2005; received in revised form 14 April 2006; accepted 3 May 2006 Available online 23 June 2006 Abstract Cassava starch/montmorillonite composite films were prepared by casting. This research was focused on the exploitation of chitosan as a compatibilising agent in order to homogeneously disperse the clay particles in a starch matrix. Mixtures of cassava starch, mont- morillonite (MMT), chitosan, glycerol as a plasticizer, and distilled water adjusted to pH 3 by acetic acid addition was well mixed with a homogenizer and gelatinized by heating to temperatures of 70–80 °C. The obtained homogeneous starch solution was cast onto an acrylic mold and allowed to dry in open air. X-ray diffraction of the dried film revealed that after treatment with chitosan the interlayer spacing of montmorillonite slightly increased from 14.78 A ˚ to 15.80 A ˚ , providing information that chitosan was too large to intercalate into clay the gallery in order to pro- duce the nanocomposite. Despite the unachieved state of nanocomposite, the evidence from SEM showed that a finer size of clay par- ticles was obtained in the case of the composite film containing chitosan. The results indicated that chitosan due to its hydrophilicity and capability of attaching to the clay surface played a role in compatabilising between starch matrix and montmorillonite. As a result, the starch/MMT composite film at low MMT content exhibited an improvement in tensile properties due to a reinforcement effect. It was also found that the surface hydrophobicity of the composite film increased with an increase in chitosan content. In association with film hydrophobicity, the water vapor transmission rate and moisture absorption were found to decrease with an increase in chitosan content. Ó 2006 Elsevier Ltd. All rights reserved. Keywords: Cassava starch/montmorillonite composite film; Chitosan; Mechanical and physical properties 1. Introduction There has been a growing interest in the use of biode- gradable polymers for packaging materials in order to reduce the environmental pollution caused by plastic wastes. Starch is known to be completely biodegradable in soil and water and inexpensive. Several studies have been carried out on starch-based films obtained by melt process- ing or casting from a solution or gel with addition of plast- icizers. Even so, starch films have poor mechanical properties, brittleness, and sensitivity to water when compared to those of synthetic polymers due to their hydrophilic nature to control. In order to improve the mechanical properties and water resistance, starch can be modified by several methods such as blending with synthet- ic (Arvanitoyannis, Biliaderis, Ogawa, & Kawasaki, 1998; Bhattacharya, 1998; Wu & Zhang, 2001) or natural poly- mers (Coffin, Fishman, & Cooke, 1995; Xu, Kim, Hanna, & Nag, 2005), preparing in the composite form (Wilhelm, Sierakowski, Souza, & Wypych, 2003), and by crosslinking (Simkovic, Laszlo, & Thompson, 1996). Recently, special attention has been paid to montmorillonite minerals in the field of nanocomposites because of their small particle size, extremely large surface areas, and intercalation properties. Montmorillonite is composed of silicate layers that are 1 nm thick in planar structure and 200–300 nm in the lat- eral dimension. The typical chemical structures of mont- morillonite usually consist of two fused silica tetrahedral sheets sandwiching an edge-shared octahedral sheet of 0144-8617/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.carbpol.2006.05.012 * Corresponding author. Tel.: +66 22185544; fax: +66 22185561. E-mail address: kawee@sc.chula.ac.th (K. Srikulkit). www.elsevier.com/locate/carbpol Carbohydrate Polymers 67 (2007) 155–163