Clay-Reinforced Epoxy Nanocomposites: Synthesis, Properties, and Mechanism of Formation

Abstract

Epoxy-clay nanocomposites have been synthesized by exfoliation of organoclays during the epoxy thermosetting process. The extent of silicate layer separation is governed by the chain length of gallery cations, the clay layer charge density and the acidity of the gallery cations. By using different curing agents, we obtained both glassy and rubbery epoxy matrices. Reinforcement was substantially greater for the rubbery matrix. Both the tensile strength and the modulus of the rubbery epoxy-clay nanocomposite increased with increasing clay content. The reinforcement provided by the silicate layers at 15 wt% loading was manifested by a more than ten-fold improvement in tensile strength. The rubbery state of the matrix may allow alignment of the exfoliated silicate layers upon applying strain, thereby enhancing reinforcement.The properties of hybrid organic-inorganic composite materials are greatly influenced by the length scale of component phases. Nanoscale dispersion of the inorganic component typically optimizes the mechanical properties of the composite. One successful approach to enhancing inorganic particle dispersion is the in situ polymerization of metal alkoxides in organic polymer matrices via the sol-gel process (1, 2). In these systems the inorganic components are formed by the hydrolysis and condensation of mononuclear precursors, such as tetraethoxysilane (TEOS).Inorganic materials that can be broken down into their nanoscale building blocks can be superior alternatives to the sol-gel process for the preparation of nanostructured hybrid organic-inorganic composites (3). For instance, the exfoliation of the 10 Â-thick layers of smectite clays in polymer matrices is one such promising route to nanocomposite formation. Ion exchange of the Na + or Ca 2+ gallery cations in the pristine mineral by organic cations allows modification

Preparation and properties of unsaturated polyester–montmorillonite intercalated hybrid

“…Due to their low density, excellent mechanical properties, and outstanding diffusional barrier properties, a lot of nanocomposites based on other thermoplastic polymers, such as poly(1-caprolactone), 2 poly(ethylene oxide), 3 polystyrene, 4 polypropylene, 5 poly(ethylene terephthalate), 6 polyurethane, 7 polyacrylate, 8 poly(methyl methacrylate), 9 and poly(styrene/maleic anhydride) 10 have been investigated. Recently, investigations on the nanocomposites prepared from thermoset polymers, such as epoxy resin, [11][12][13][14][15] unsaturated polyester, 16 -18 silicone rubber, 19,20 and polyimide, 21 have drawn great interest. The research results of Pinnavaia's group 11 showed that the tensile strength and modulus of the nanocomposite of epoxide resin with 7.5% of organophilic montmorillonite increase by 10 times.…”

“…Recently, investigations on the nanocomposites prepared from thermoset polymers, such as epoxy resin, [11][12][13][14][15] unsaturated polyester, 16 -18 silicone rubber, 19,20 and polyimide, 21 have drawn great interest. The research results of Pinnavaia's group 11 showed that the tensile strength and modulus of the nanocomposite of epoxide resin with 7.5% of organophilic montmorillonite increase by 10 times. Those materials were produced either by melt intercalation of thermoplastics or in situ polymerization of intercalated monomers or by cross-linking (curing) of intercalated oligomers.…”

Competitive interactions, structure and properties in polymer/layered silicate nanocomposites

“…At the dawn of nanocomposite research all composites containing an organophilized layered silicate were claimed to have exfoliated structure [32,[43][44][45]. Since more detailed investigations showed that this is not true, structure changed to exfoliated/intercalated instead [5,16,46], but the complexity of structure was still largely ignored.…”

New method for the synthesis of clay/epoxy nanocomposites

“…Areas such as the effect of curing processes, 4 promoters (catalysts), 4,5 choice of clays, 6 choice of curing agents, 7 choice of intercalating agents with alkylammonium ion with different alkyl chain lengths and different head groups (primary, secondary, tertiary and quaternary alkylammonium), 8 and corresponding morphological, mechanical, chemical, thermal, and rheological properties have been researched.…”