Mechanism of Exfoliation of Nanoclay Particles in Epoxy−Clay Nanocomposites

Park, Jong Hyun; Jana, Sadhan C.

doi:10.1021/ma021509c

Cited by 325 publications

(211 citation statements)

References 46 publications

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“…In recent years numerous research activities on polymer-clay nano-composites have been performed. However, the matrices of polymer-clay nanocomposites are mainly synthetic thermosetting [177][178][179] as well as thermoplastics polymers [180][181][182][183][184][185] but of late biodegradable plastics have found place even though limited, for example, PlA 186 and PCl 187 have also been used for the processing of nanocomposites with a layered silicate. However, the materials prepared from natural polymers have poor performance compared with those prepared from synthetic polymers.…”

Section: Bio Nano-compositesmentioning

confidence: 99%

Environment Friendly Composite Materials: Biocomposites and Green Composites

Mitra

2014

DSJ

166

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IntroductIonDevelopment of advanced polymer composite materials having superior mechanical properties opened up new horizons in the engineering field. Advantages such as corrosion resistance, electrical insulation, easy processability at relatively less energy requirement in tooling and assembly costs, higher stiffness and strength, fatigue resistance and lower weight than metals have made polymer composite widely acceptable in structural applications. The so-called advanced composites have replaced metals because of their excellent mechanical properties and low density giving them high specific strength and stiffness 1 . Such weight savings are highly desirable for applications in aerospace to transportation to reduce weight and associated fuel consumption. Another distinct advantage is their ability to be engineered to obtain required properties in different directions by appropriate fiber placing in different layers of the laminated structure.Composite properties depend on the properties of the constituent materials i.e. the fibers and resins used. The strength and stiffness of the composites are directly a function of the reinforcing fiber properties which carry most of the load and their volume content. The resin helps to maintain the relative position of the fibers within the composite and, more importantly, transfers the load from the bottom fibers to the intact fibers. As a result, fiber/resin interfacial properties are also important and have a significant effect on composite properties including toughness and transverse fracture stress. To fabricate high strength composites, all three factors namely fiber properties, resin properties as well as fiber/resin interface characteristics are critical.Currently most of the fibers and resins are derived from petroleum feed stocks and do not degrade for several decades under normal environmental conditions 2 . Composites made from thermosetting resins cannot be reprocessed or recycled, however, a small fraction of these thermosetting composites are crushed into powder used as filler or incinerated to obtain energy in the form of heat, most of them end up in land-fills at the end of their life. In anaerobic conditions, such as those in land -fills, the petroleum based composites may not degrade making that land unavailable for any other use. On the other hand, incineration produces toxic gases and requires expensive scrubbers. Both incineration and dumping in land-fills are environmentally undesirable as well as expensive. In the future, these methods of disposing of composites are expected to get even more expensive as the pollution laws all over the world get stricter and the number of land -fills decline. In addition, at the present rate of consumption, the world petroleum resources are estimated to last for the next 50 years or so 2 . Thus, there is a great interest generated in developing green composites using fully sustainable, biodegradable, environment friendly and annually renewable fibers and resins, particularly those derived from plants 3 . A variet...

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Section: Bio Nano-compositesmentioning

confidence: 99%

Environment Friendly Composite Materials: Biocomposites and Green Composites

Mitra

2014

DSJ

166

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“…[31][32][33] Acetone, which was used as a dispersing agent for nanoclay, can easily penetrate clay galleries and enable epoxy resin to be placed between clay layers before the curing process.…”

Section: Structure Characterizationmentioning

confidence: 99%

Preparation and property evaluation of nanocomposites based on polyurethane‐modified epoxy/montmorillonite systems

Bakar¹,

Kostrzewa²,

Hausnerová³

et al. 2010

Adv Polym Technol

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Montmorillonite nanoclay and polyurethanes obtained from polyethylene glycol (PUR 400) and polyoxypropylene diol (PUR 1002) were used to enhance the mechanical properties of an epoxy resin. Maximum impact strength improvement was obtained with compositions containing 2% nanoclay and 10% PUR 400 as well as that with 1% nanoclay and 15% PUR 400, corresponding to 110% and 75%, respectively, in relation to the unmodified epoxy resin. Moreover, a 10-fold increase was observed with respect to the flexural strain at break for the composition containing 15% PUR 1002 and 2% nanoclay.

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“…Park and Jana [29] investigated the mechanism of exfoliation of nanoclay particles in epoxy-clay nanocomposites. They suggested that the elastic force exerted by crosslinked epoxy molecules in the clay galleries were responsible for exfoliation of clay layers from the intercalated tactoids.…”

Section: The Role Of Intercalation and Diffusionmentioning

confidence: 99%

Estimation of stresses required for exfoliation of clay particles in polymer nanocomposites

Borse¹,

Kamal²

2008

Polymer Engineering & Sci

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The dispersion of clay in a polymer matrix is influenced by two factors: the choice of organic treatment for the clay and the processing or mixing method. Maximum benefits are achieved when the platelets are well dispersed or exfoliated. Exfoliated nanocomposites are formed when the individual clay layers break off the agglomerated particles or tactoids and are either randomly dispersed in the polymer (a disordered nanocomposite) or left in an ordered array. It is suggested that size reduction of clay particles and platelet delamination occur by erosion or surface peeling. A model based on the classical theories of interparticle interactions was formulated for the exfoliation of the clay platelets in a polymer matrix. The model involves the estimation of the binding energy and the adhesive force between the platelets in a clay particle, which indicate the forces required for breaking apart or delamination of clay particles. Then, the shear force required for breakup or delamination of the tactoids is estimated and compared to the hydrodynamic shear forces available during processing. POLYM INTRODUCTIONPolymer/clay nanocomposites are materials composed of a polymer matrix and nanometer size clay particles. They exhibit significant improvements in tensile modulus and strength and reduced permeability to gases and liquids, in comparison with the pure polymer. These property improvements can be realized, while retaining clarity of the material with a little increase in density, since the typical clay loading is 2-5 wt%. It is well known that some polymers interact with montmorillonite and that the clay surface can act as an initiator for polymerization [1,2]. However, clay/polyamide-6 (PA-6) nanocomposites were commercialized mainly after practical methods were developed for appropriate dispersion of the clays at the nanometer scale [3].The first step in achieving nanoscale dispersion of clays in polymers is to expand the galleries and to match the polarity of the polymer or monomer, so that it will intercalate between the layers [4]. This is done by exchanging an inorganic cation, generally sodium cation present in the clay, with an organic cation of a quaternary ammonium compound. The larger organic cations swell the layers and increase the hydrophobic (or organophilic) properties of the clay [5], resulting in an organically modified clay. The organically modified clay can then be intercalated with polymer by several routes. Highly polar polymers, such as polyamides and polyimides, are more easily intercalated than nonpolar polymers, such as polypropylene and polyethylene [6,7]. Melt intercalation involves mixing the clay and polymer melt, with or without shear. Nanocomposites can have several structures. Intercalated nanocomposites usually appear as tactoids with expanded interlayer spacing, but the clay basal spacing remains in the few nanometer range. Exfoliated nanocomposites are formed when the individual clay layers break off the tactoid and are either randomly dispersed in the polymer (a disordered nanocom...

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Mechanism of Exfoliation of Nanoclay Particles in Epoxy−Clay Nanocomposites

Cited by 325 publications

References 46 publications

Environment Friendly Composite Materials: Biocomposites and Green Composites

Environment Friendly Composite Materials: Biocomposites and Green Composites

Preparation and property evaluation of nanocomposites based on polyurethane‐modified epoxy/montmorillonite systems

Estimation of stresses required for exfoliation of clay particles in polymer nanocomposites

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