Preparation and Properties of a Carboxyl-Terminated Butadiene Acrylonitrile Toughened Epoxy/Montmorillonite Nanocomposite Hun-Bong Lee, Ho-Gyum Kim, Keun-Byoung Yoon, Dong-Ho Lee, Kyung-Eun Min Department of Polymer Science, Kyungpook National University, Daegu, Korea Received 14 August 2007; accepted 7 November 2007 DOI 10.1002/app.30111 Published online 24 March 2009 in Wiley InterScience (www.interscience.wiley.com). ABSTRACT: The influence of the montmorillonite type and concentration on the mechanical properties and mor- phology of a carboxyl-terminated butadiene acrylonitrile toughened epoxy/montmorillonite nanocomposite has been studied. Modified montmorillonite can be well dis- persed in a carboxyl-terminated butadiene acrylonitrile toughened epoxy/montmorillonite nanocomposite. Jeff- amine, a curing agent, contributes to the intercalation of sodium montmorillonite, allowing the loss of the ordered layered structure in the nanocomposite. The preparation method of the nanocomposite has a slight effect on the mechanical properties. V V C 2009 Wiley Periodicals, Inc. J Appl Polym Sci 113: 685–692, 2009 Key words: mechanical properties; morphology; nanocomposites; organoclay; rubber INTRODUCTION Polymer layered silicates such as montmorillonite (MMT) nanocomposites are used for various prod- ucts because of their improved mechanical and bar- rier properties, chemical resistance, and thermal stability even with a small amount of MMT. 1–10 MMT has a high aspect ratio typically ranging from 100 to 1500 and unique intercalation/exfoliation characteristics. 11,12 To obtain a high degree of inter- calation/exfoliation of the layered silicate in the polymer matrix, it is essential that the cations pres- ent in the layered silicate be exchanged with organic cations. 13–19 The desire to prepare epoxy nanocom- posites exists because a reinforcing effect of less than 10 times can be achieved with an MMT loading of only 7.5 vol %. 20 Wang and Pinnavia 21 prepared an epoxy nanocomposite containing organomodified clay and suggested that the curing rate and the type of organomodifier should be severely controlled to acquire an exfoliated nanocomposite because acidic onium ions in MMT galleries promote intragallery polymerization rather than extragallery polymeriza- tion. In several studies, researchers have attempted to use polyoxypropylene (Jeffamine), the usual cur- ing agent for epoxy resins, as an organic modi- fier. 18,21 Jang et al. 19 showed that exfoliation is achieved with a polymer matrix with a high solubil- ity parameter because of the strong electrostatic attractions between the intergallery cations and poly- mer chain. This result also demonstrates that in situ polymerization is a more efficient process than con- ventional melt blending for the desired morphology. In a series of investigations, we examined how a low loading of organically modified MMT yields a carboxyl-terminated butadiene acrylonitrile (CTBN) toughened epoxy resin with improved impact strength and toughness. We also confirmed that this result is consistent with observations of a CTBN- toughened epoxy resin including sodium montmoril- lonite (Na-MMT). 22 In this study, CTBN-toughened epoxy/MMT nanocomposites were prepared to explore the influ- ence of chemical properties of CTBN on the mechan- ical properties of the polymer and the possibility of exfoliated nanocomposites with Na-MMT in in situ polymerization. EXPERIMENTAL Materials A bisphenol A epoxy resin (YD-128) was purchased from Kukdo Chemical (Seoul, Korea). The toughen- ing and curing agents were CTBN (Hycar 13008, B.F. Goodrich, Greenville, SC) and Jeffamine D-400 (Huntsman Co., USA). Organically modified MMT (Cloisite 30B) with an ion-exchange capacity of 90 mequiv/100 g and Na-MMT (Cloisite-Na) were obtained from Southern Clay Co. (Gonzales, TX). Journal of Applied Polymer Science, Vol. 113, 685–692 (2009) V V C 2009 Wiley Periodicals, Inc. Correspondence to: K.-E. Min (minkye@knu.ac.kr).