Modification of Physico-Mechanical Properties of Chitosan-Tapioca Starch Blend Films Using Nano Graphene Alireza Ashori and Reza Bahrami Department of Chemical Technologies, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran Biodegradable blend films from chitosan-tapioca starch were prepared by the casting method. To improve the properties of chit- osan–starch blend films, nano graphene was used. The influences of the loading of graphene on the physico-mechanical properties in terms of water vapor transmission rate (WVTR), thermal stability, and tensile strength of the blend films were investigated. Scanning electron microscopy (SEM) and FTIR were used to investigate the surface morphology and molecular interaction of the blend films, respectively. After the incorporation of nano graphene, the blend film from chitosan-starch showed an increase in tensile strength and thermal stability, and a decrease in WVTR and elongation at the break. These results showed that the combination of a tiny amount of graphene presents a promising method for improving the mechanical and barrier properties of chitosan-starch biocompo- site films. The SEM observations indicated that a high amount (3 wt.%) of graphene was easily agglomerated. This caused the mechanical properties of the composite films to be reduced. Among the various compositions studied, chitosan-starch film filled with 0.8 wt.% graphene showed superior properties. The structural properties investigated by FTIR showed a clear interaction between chitosan and starch, forming a new material with enhanced mechan- ical properties. Keywords Blend film; Chitosan; Graphene; Tapioca starch; Tensile strength INTRODUCTION The interest in biodegradable films and films made from renewable and bio-based polymers has increased over the last few years [1,2] . Biopolymer materials present the possibil- ity of obtaining thin films and coatings for covering fresh or further processed foods to extend their shelf life [3] . Not only can edible films made from natural biopolymers improve handling properties and extend shelf life of food products, but they can also relieve the pressure on environment caused by plastic packaging wastes [4] . Edible films and coatings offer some advantages such as edibility, biocompatibility, aesthetic appearance, barrier properties, nontoxicity, nonpolluting and low cost [5] . Many bio-based materials may be utilized for making green packaging films including proteins, polysaccharides, and lipids [6] . Among these natural biopolymers, chitosan, an important derivative produced by deacetylation of chitin, is one of the most attractive materials because of its many unique properties. It has been proved to be nontoxic, biodegradable, biofunctional, and biocompatible and has antimicrobial characteristics [7–9] . Furthermore, chitosan films are tough, long-lasting, flexible, and very difficult to tear [10] . Chitosan has been used in various applications, such as medical, pharmaceutical, textile, water treatment, food, cos- metics, packaging, etc. [11–13] . However, pure chitosan film has relatively poor water barrier and mechanical properties. To improve the physical and functional properties of chitosan films, blending with other natural biopolymers has been proposed [2,14] . There are some reports about chitosan-blended films in open access literature such as chitosan-whey protein films [15] , chitosan methylcellulose films [16] , chitosan-gelatinfilms [17] , and chitosan-pea starch films [18] . Starch-based films have been considered particularly because they exhibit physical characteristics similar to syn- thetic polymers: transparent, odorless, tasteless, semiperme- able to CO 2 and resistant to O 2 passage [19,20] . According to the Food and Agriculture Organization [21] , one important source of starch in South America is tapioca. Therefore, the use of tapioca starch to develop edible films and coatings has been considered [22] . However, wide applications of starch film are limited by its water solubility and brittle- ness [23] . To overcome these shortcomings, starch is blended with different proteins to decrease the water vapor permea- bility of the films and to increase their tensile strength [24] . The blending of starch and chitosan is an alternative way, which not only improves the mechanical and water vapor barrier properties, as well as the antimicrobial attributes of starch film, but also reduces the cost and enhances the bio- degradability of chitosan film [14] . The aim of this work is to prepare and characterize the performance of chitosan–tapioca starch based films. Address correspondence to A. Ashori, Department of Chemi- cal Technologies, Iranian Research Organization for Science and Technology (IROST), P. O. Box 15815-3538, Tehran, Iran. E-mail: ashori@irost.org Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lpte. Polymer-Plastics Technology and Engineering, 53: 312–318, 2014 Copyright # Taylor & Francis Group, LLC ISSN: 0360-2559 print=1525-6111 online DOI: 10.1080/03602559.2013.866246 312