Thermal properties of ethylene octene copolymer (Engage)/ dimethyldioctadecyl quaternary ammonium chloride-modiﬁed montmorillonite clay nanocomposites Ganesh Latta Quentin Lineberry Riko Ozao Hou-Yin Zhao Wei-Ping Pan Received: 16 October 2007 / Accepted: 10 January 2008 / Published online: 20 February 2008 Ó Springer Science+Business Media, LLC 2008 Abstract The nanocomposites of ethylene octene copolymer (Engage Ò ) with an organically modiﬁed (dimethyldioctadecyl quaternary ammonium chloride) montmorillonite (M-MMT) clay were synthesized by using a solution intercalation tech- nique. The intercalation of M-MMT layers for M-MMT loading of 2.5–7.5% was veriﬁed by the shift of X-ray diffraction peak to a lower angle, showing change in basal d-spacing from 1.26 for M-MMT to 1.35 nm. Internal structure and the dispersion state of M-MMT in the nanocomposites were observed by transmission electron microscope, which conﬁrmed the clay in the intercalated state. Thermomechanical analysis results showed improved dimensional stability under compression at 30 °C for nanocomposites with increasing M-MMT. By DMA, the storage moduli of nanocomposites below glass transition temperature were higher than the neat Engage and increased with increasing M-MMT content. The glass transition temperature was lowest for the nanocomposite containing 2.5% M-MMT (E-2.5M-MMT), suggesting the optimal concentration of M-MMT in nanocomposite being 2.5% or higher from the viewpoint of thermal properties. The oxidation induction time (OIT) of the nanocomposites was obtained by using pressure-differential scanning cal- orimeter. The Engage/M-MMT nanocomposites were superior in thermal oxidation resistance as compared to the neat Engage, with E-5.0M-MMT yielding highest OIT time value. Introduction In the past two decades, the research in polymer/layered silicate nanocomposite has attracted the interests of aca- demics and industries due to their improved mechanical, thermal, ﬂame retardation, ablation resistance, and enhanced barrier properties [1–6]. Montmorillonite, more speciﬁcally a 2:1 phyllosilicate consisting of layers built by two silica tetrahedral sheets and one octahedral sheet of aluminum or magnesium hydroxide, has been well recog- nized to improve the mechanical strength and thermal properties of the polymer to which it is added [7–9]. By isomorphic substitution of Al 3+ by divalent (Fe 2+ or Mg 2+ ) cations, negative charge is generated, which is counterbal- anced with cations such as Li + , Na + , Ca 2+ . Such layers organize themselves as parallel layers with a regular van der Waals gap (called interlayer or gallery). It is also common to render the originally hydrophilic surface organophilic by exchanging the alkali counterions with cationic organic surfactants such as alkylammoniums [10]. The addition of organically modiﬁed montmorillonites (M-MMTs) to polymers further imparts ﬂame retardancy, barrier proper- ties, and ablation resistance to the resulting composite due to nanoscopic distribution and to a synergetic effect of the nano-sized crystals with the polymer chains [11]. Polymer/layered silicate nanocomposites are synthe- sized by four techniques: in situ polymerization, intercalation from polymer solution, intercalation by polymer melt or melt intercalation, and sol–gel technique [12]. The melt intercalation technique is a low-cost method by which the polymer chain can be intercalated into the galleries of clay by heating the polymer and organo–clay mixture to the glass transition temperature or the melting temperature of polymer. The mobile polymer chain can diffuse into the clay galleries and expand the silicate layer G. Latta  Q. Lineberry  R. Ozao  H.-Y. Zhao  W.-P. Pan Thermal Analysis Laboratory, Institute for Combustion Science and Environmental Technology, Western Kentucky University, Bowling Green, KY 42101, USA R. Ozao (&) SONY Institute of Higher Education, Atsugi, Kanagawa, Japan e-mail: ozao@aoni.waseda.jp 123 J Mater Sci (2008) 43:2555–2561 DOI 10.1007/s10853-008-2468-6