Macromolecular Nanotechnology The effect of composition and draw-down ratio on morphology and oxygen permeability of polypropylene nanocomposite blown films Amin Mirzadeh, Mehrdad Kokabi * Polymer Engineering Group, Chemical Engineering Department, Faculty of Engineering, Tarbiat Modares University, P.O. Box 14115-143, Tehran, Islamic Republic of Iran Received 6 December 2006; received in revised form 20 May 2007; accepted 10 June 2007 Available online 24 June 2007 Abstract Polypropylene nanocomposite blown films containing organoclay were prepared by melt extrusion followed by film blowing. The effect of quantity of organically modified montmorillonite, and the compatibilizer (polypropylene-g-maleic anhydride, PP-g-MA), also the draw-down ratio on the morphology and oxygen permeability of nanocomposite films were investigated. Various characterization instruments were employed to identify the morphology, crystallinity, and dynamic mechanical properties of nanocomposite films. The oxygen permeability coefficient was evaluated based on ASTM D1434. X-Ray diffractometry pattern for the most impermeable sample shows that the morphology of nanocomposite film is a coexistence of intercalated tactoids and exfoliated layers which is confirmed by transmission electron microscope micro- graphs. The results show that the oxygen permeability coefficient is influenced by the quantity of organoclay and compa- tibilizer, also the morphology and orientation of layered silicate. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Polypropylene; Montmorillonite; Nanocomposite; Oxygen permeability; Blown film; Draw-down ratio 1. Introduction Common barrier thermoplastic polymers such as polyvinylidine chloride (PVDC) and ethylene vinyl alcohol (EVOH) resin cannot be employed as monolayer due to some limitations such as process- ing difficulties and health care criteria. In recent years, extensive works have been carried out on pro- duction of monolayer barriers [1]. The polymer/clay nanocomposites are the best candidates for this pur- pose [2]. The mixing of organoclay with a polymer is mostly performed in melt state in some types of screw compounder. Intercalation and delamination (exfoliation) are two morphological characteristics related to montmorillonite layers obtained by com- pounding. The intercalation is the state when in the nanocomposite there are well ordered multi-layered structures with the extended polymer chains inserted into interlayers. The delaminated or exfoli- ated state gives a structure with separate silicate lay- ers. Both intercalated and exfoliated structures may 0014-3057/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.eurpolymj.2007.06.014 * Corresponding author. Tel.: +98 21 8801 1001; fax: +98 21 8800 6544. E-mail address: mehrir@modares.ac.ir (M. Kokabi). European Polymer Journal 43 (2007) 3757–3765 www.elsevier.com/locate/europolj EUROPEAN POLYMER JOURNAL MACROMOLECULAR NANOTECHNOLOGY