ISSN 0965-545X, Polymer Science, Ser. A, 2011, Vol. 53, No. 1, pp. 75–84. © Pleiades Publishing, Ltd., 2011. Original Russian Text © A.P. Korobko, S.V. Krasheninnikov, I.V. Levakova, S.N. Drozd, S.N. Chvalun, V.V. Nikolaev, M.A. Shcherbina, S.V. Cherdyntseva, 2011, published in Vysokomolekulyarnye Soedineniya, Ser. A, 2011, Vol. 53, No. 1, pp. 78–87. 75 1 INTRODUCTION Epoxy resins are widely used as matrices for prepa- ration of epoxy cured materials: coatings, glues (adhe- sives), potting compounds, and adhesives for rein- forced plastics for civil and special-purpose branches of industry [1, 2]. Because of their mechanical characteristics (high elastic modulus, low creep), chemical resistance, low shrinkage during curing, and relatively low cost, cured epoxy composites have evident advantages over many other thermosetting polymers [3, 4]. Nevertheless, for many applications, it is desirable to improve the following characteristics of the epoxy polymers: impact toughness (reduced brittleness), barrier characteristics (reduced permeability), flame retardancy (reduced flammability), and thermal and heat resistance (increased glass-transition tempera- ture). In recent years, a new approach to the improve- ment of characteristics of polymer materials (both thermoplastics and thermally setting plastics) has been advanced; this approach includes incorporation of aluminosilicate platelets into the polymers and devel- 1 This work was supported by the Federal Agency for Science and Innovation, Ministry of Education and Science, project code 02.513.11.3445. opment of silicate–polymer nanocomposites [5–9]. Since the thickness of an aluminosilicate platelet is 1 nm and its aspect ratio is high (about 1000), alumi- nosilicate platelets can critically improve many char- acteristics of diverse polymers, even at relatively low concentrations [10–13]. One of the most important characteristics of poly- mers, including epoxy polymers, is their thermal resis- tance. One remarkable example is known: when the heat distortion temperature of Nylon-6 (semicrystal- line polymer) was increased more than twice only via the introduction of a few percent of aluminosilicate [14]. In addition, the proper choice of aluminosili- cates improves the heat resistance of fully amorphous thermoplastics [15–18]. Usually, improvement in the characteristics (including heat resistance) of silicate–polymer nano- composites is assumed to be directly related to the complete exfoliation of the silicate platelets in the polymer. However, this assumption is not always justi- fied for epoxy polymers (typical representatives of the family of thermosetting plastics) and especially for epoxy polymers that exist at room temperature in the glassy state (with a high glass-transition temperature). The mechanism behind the effect of aluminosili- cates on the glass-transition temperature of epoxy nanocomposites has remained vague, even though Effect of the Chemical Grafting of Epoxy Resin onto Organomodified Montmorillonite on the Structure and Heat Resistance of an Epoxy Nanocomposite 1 A. P. Korobko a , S. V. Krasheninnikov a , I. V. Levakova a , S. N. Drozd a , S. N. Chvalun a , V. V. Nikolaev b , M. A. Shcherbina a , and S. V. Cherdyntseva a a Karpov Institute of Physical Chemistry, ul. Vorontsovo pole 10, Moscow, 105064 Russia b OOO Galen, Kombinatskaya ul. 4, Cheboksary, 428008 Chuvash Republic, Russia e-mail: korobko@cc.nifhi.ac.ru Received April 22, 2010; Revised Manuscript Received June 8, 2010 Abstract—It is shown that the noncatalyzed chemical grafting of an epoxy oligomer onto the surface of montmorillonite platelets may proceed via the reaction between the epoxy groups and the hydroxyl groups of the organic modifying agent of the layered aluminosilicate. The effect of grafting on the structure and heat resistance of the cured epoxy nanocomposite is studied. Complete exfoliation of montmorillonite particles into individual platelets is shown to be a necessary but insufficient condition for increasing the glass-transi- tion temperature of the nanocomposite relative to that of the initial matrix. A much higher contribution to the increase in the glass-transition temperature is ensured by grafting of epoxy molecular chains onto the sur- face of aluminosilicate platelets; i.e., strong covalent matrix–aluminosilicate bonds form in addition to phys- ical bonds, a process that entails development of a thicker three-dimensional network. DOI: 10.1134/S0965545X11010032 COMPOSITES