Studies on Nylon-6/EVOH/Clay Ternary Composites N. Artzi, B.B. Khatua, M. Narkis Department of Chemical Engineering, Technion—Israel Institute of Technology, Haifa 32000, Israel A. Siegmann Department of Materials Engineering, Technion—Israel Institute of Technology, Haifa 32000, Israel Nylon-6 (Ny-6)/EVOH blends are interesting host mul- tiphase systems for incorporation of low clay contents. The Ny-6/EVOH blend is a unique system, which tends to chemically react during melt-mixing, affecting thermal, morphological and mechanical properties of the ternary systems containing clay. The addition of clay seems to interrupt the chemical reaction between the host poly- mers at certain compositions, leading to lower blending torque levels when clay is added. A competition between Ny-6 and EVOH regarding the intercalation process takes place. Ny-6 seems to lead to exfoliated structure, whereas EVOH forms intercalated structure, as revealed from XRD and TEM analyses, owing to thermodynamic considerations and preferential localization of the clay in Ny-6. Hence, the ternary systems have combined inter- calated and delaminated morphology or complete exfo- liated morphology depending on blend composition and clay content. Selective extraction experiments (gel con- tent) indicate the formation of chemical reaction be- tween the Ny-6 and EVOH, and give an indirect indica- tion of the polymer content residing in the galleries. The thermal properties of the polymers were found to be affected by the occurrence of chemical reaction, the level of intercalation and exfoliation and plasticizing ef- fect of the low molecular weight onium ions treating the clay. Of special interest is the increased storage modu- lus attained upon the addition of only 1.5 wt% clay. POLYM. COMPOS., 27:15–23, 2006. © 2005 Society of Plastics Engineers INTRODUCTION Nanocomposite materials consisting of organic polymers and inorganic clay have recently evoked intense research interests owing to their unique characteristics [1]. From the point of view of obtaining improved physical/mechanical properties of nanocomposites, exfoliation is preferred to intercalation. In general, intercalation is observed when the polymer matrix and the clay have intermediate interaction levels, while exfoliation is observed when the polymer and the clay have strong attractive interactions. Hence, as in the preparation of immiscible polymer blends, compatibility between the polymer and clay is desired [2]. Multiphase polymer blends have been of great impor- tance in the development of new synthetic materials. How- ever, polymer blends usually result in heterogeneous, two, or multiphase materials exhibiting poor properties. Al- though the limited components miscibility is sometimes used to improve specific properties, generally immiscibility of the polymers hinders utilization of their blends. The general challenge of polymer blending is to overcome the low entropy of mixing and unfavorable enthalpy of mixing typical of most high molecular weight polymers. The achievement of compatibilization, whether by addition of a third component (i.e., compatibilizer) or by in situ chemical reactions between the blend’s components (reactive blend- ing) has played an important role in the development of polymer blends [3]. Ethylene vinyl alcohol (EVOH) copol- ymers appear to have the potential of forming compatible or even miscible blends in the amorphous state with a variety of polymers containing functional groups such as esters, methacrylates, acetoxys, ethers, and the like [4]. The tech- nological incentive toward nylon/EVOH blends is in pack- aging applications. Polyamides are engineering semicrystal- line thermoplastics having low permeability for CO 2 , while EVOH copolymers are semicrystalline materials showing excellent oxygen barrier properties in their dry state [5]. Nanocomposites based on organoclays and homopoly- mers have been extensively investigated; however, nano- composites based on organoclays dispersed in immiscible polymer blends are relatively rare although novel materials, which combine the properties of polymer blends and nano- metric clays, can be visualized. It is expected that such materials will differ in the level of clay dispersion (e.g., the extent of exfoliation/intercalation of layered silicates) and the blend phase morphology (e.g., the average size of phase- separated domains) compared with single polymer/clay Correspondence to: M. Narkis; e-mail: narkis@tx.technion.ac.il Contract grant sponsor: Levi Eshkol scholarship of the Israel Ministry of Science. DOI 10.1002/pc.20157 Published online in Wiley InterScience (www.interscience.wiley. com). © 2005 Society of Plastics Engineers POLYMER COMPOSITES—2006