Reactive blending of thermoplastic starch, epoxidized natural rubber and chitosan Kittisak Jantanasakulwong a,⇑ , Noppol Leksawasdi a , Phisit Seesuriyachan a , Somchai Wongsuriyasak a , Charin Techapun a , Toshiaki Ougizawa b a School of Agro-Industry, Faculty of Agro-Industry, Chiang Mai University, Mae-Hea, Mueang, Chiang Mai 50100, Thailand b Department of Chemistry and Materials Science, Tokyo Institute of Technology, 2-12-1-S8-33, O-okayama, Meguro-ku, Tokyo 152-8552, Japan article info Article history: Received 22 June 2016 Received in revised form 12 September 2016 Accepted 21 September 2016 Available online 22 September 2016 Keywords: Thermoplastic starch (TPS) Epoxidized natural rubber (ENR) Chitosan (CTS) Reaction Epoxy abstract Thermoplastic starch (TPS) was prepared by melt blending cassava starch and glycerol (70/30) at 140 °C. Chitosan (CTS) was incorporated during TPS preparation. The TPS/CTS sample was melt blended with epoxidized natural rubber (ENR) at 140 °C. In the TPS/ENR/CTS blend, adding CTS and ENR improved the tensile strength and elongation at break, respectively. Morphology of the TPS/ENR blend showed the dispersion of large- sized ENR particles in the TPS matrix. Adding CTS reduced the size of the ENR particles. Incorporating CTS also enhanced the melt viscosity of the blend, which suggested a reaction between CTS and ENR. FTIR confirmed that the amino groups of CTS reacted with the epoxy groups of ENR. This reaction between the CTS amino groups with the ENR epoxy groups improved the mechanical properties of the TPS/ENR/CTS blend. Ó 2016 Published by Elsevier Ltd. 1. Introduction Thermoplastic starch (TPS) can be prepared by blending starch with a plasticizer, such as water, glycerol or sorbitol [1]. The plasticizer penetrates into the granules of the starch, interrupting its crystalline structure and inducing the formation of an amorphous structure when subjected to high temperatures and shear forces during the melting process [2]. Therefore, the amorphous starch, following the addition of a plasticizer, behaves like a thermoplastic polymer during the melt stage. Some polymers that have been blended with TPS to improve its mechanical properties include: polypropylene [3], polyethylene [4,5], poly(lactic acid) [6–8] and poly(butylenesadipate-co-terephthalate) [9]. Natural rubber (NR) that contains epoxy groups can be modified into epoxidized natural rubber (ENR). Natural rubber can be epoxidized to various degrees: 25%, 50%, and 75% epoxidation is referred to as ENR-25, ENR-50, and ENR-75, respectively. A few studies have reported using ENR to improve the toughness of PLA [10–13]. The improved toughness of PLA by 20% epoxidized natural rubber has been reported [10]. Akbari et al. reported that adding ENR improved the impact toughness of a PLA/talc blend [11]. Wang et al. reported that dicumyl peroxide (DCP) improved the compatibility between PLA and ENR, as well as the impact toughness [13]. Little research exists on the blending of TPS with rubber. Carvalho et al. investi- gated the morphology of a TPS and natural rubber latex (NRL) blend and found that the phase morphology of the blend depended on the glycerol content [14]. ENR is used in various fields, such as polymer blends [15], polymer modification [16] and polymer composites [17]. http://dx.doi.org/10.1016/j.eurpolymj.2016.09.035 0014-3057/Ó 2016 Published by Elsevier Ltd. ⇑ Corresponding author. E-mail address: jantanasakulwong.k@gmail.com (K. Jantanasakulwong). European Polymer Journal 84 (2016) 292–299 Contents lists available at ScienceDirect European Polymer Journal journal homepage: www.elsevier.com/locate/europolj