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Exfoliated nanocomposites rubber

The lowering of die swell values has a direct consequence on the improvement of processability. It is apparent that the processability improves with the incorporation of the unmodified and the modified nanofillers. Figure lOa-c show the SEM micrographs of the surface of the extrudates at a particular shear rate of 61.2 s 1 for the unfilled and the nanoclay-filled 23SBR systems. The surface smoothness increases on addition of the unmodified filler, and further improves with the incorporation of the modified filler. This has been again attributed to the improved rubber-clay interaction in the exfoliated nanocomposites. [Pg.24]

Improvements in the reduction of flammability of polymers with low clay contents and better processability have been reported, in addition to reductions in the concentration of toxic vapors produced in the combustion stage [116-120]. In connection to their flame-retardant properties, exfoliated nanocomposites based on PP [121, 122, 115, 123], PS [115, 123, 124], poly(ethylene-vinyl acetate) [125, 126], styrene-butadiene rubber [127], PMMA [128], polyesters... [Pg.593]

Only limited success has been achieved in compounding organomontmoriUonites with styrene—butadiene rubber to prepare rubber nanocomposites [51], Knudson et al. [51] discovered that flocculation of the aqueous blend of styrene-butadiene latex and montmorOlrMiite gives an exfoliated clay-rubber nanocomposite. The approach offers the most convenient and effective method for the preparation of clay-styrene-butadiene rubber nanocomposites. [Pg.569]

Exfoliated nanocomposite, in exfoliated nanocomposites the individual layers of the nanoclay are totally delaminated and dispersed in the rubber matrix. The ordered structure of layered silicate is lost and the average distances between the exfoliated layers depend on clay loading. [Pg.307]

Intermediate nanocomposites, rubber-clay nanocomposites which are partially intercalated and partially exfoliated, are an intermediate (and often observed) type of nanocomposite. [Pg.307]

Filled polymer systems of industrial importance, e.g., filled rubber compounds, filled thermoplastics are thus meso or microcomposites, possibly with a structuration (of the dispersed phase) at the nano or meso scale. Whilst no sizeable commercial application yet exist for nanocomposites rubbers or thermoplastics (to the author s knowledge), considerable research has been made since 1984 with so-called ex-foliated layered silicate "nano-clays." Exfoliation means that individual clay sheets, of around 1 nm thickness, have been separated and adequately dispersed in the matrix. Some reinforcement has indeed been demonstrated with such exfoliated nanoparticles but, generally with very specific rubber systems and/or at a cost of preparation that is hardly compatible with reasonable chances of commercialization. [Pg.7]

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. [Pg.7]

In subsequent discussion, we will demonstrate the use and interpretation of some of these techniques. Figure 2a shows typical XRD traces of nanocomposite systems of styrene butadiene rubber (SBR) containing unmodified and modified nanoclay, describing an exfoliated and intercalated nanocomposite [5]. photographs of these systems are also given in the same figure (Fig. 2b, c). In the present case, the information obtained from both the techniques is complimentary. [Pg.10]

The morphology of rubber-based nanocomposites also seems to change in the presence of compounding ingredients [89, 90]. HNBR, when melt-compounded with organo-modified sodium montmorillonite clays (o-MMTs) prior to sulfur curing, resulted in the formation of nanocomposites with exfoliated or intercalated structures. In stark contrast, under similar conditions HNBR compounded with unmodified sodium montmorillonite clays (NA) formed microcomposites [90]. This was traced to its reactivity with the sulfur in the presence of amine-type organomodifiers. [Pg.18]

The X-ray diffraction peaks observed in the range of 3°-10° for the modified clays disappear in the rubber nanocomposites. photographs show predominantly exfoliation of the clays in the range of 12 4 nm in the BIMS. Consequently, excellent improvement in mechanical properties like tensile strength, elongation at break, and modulus is observed by the incorporation of the nanoclays in the BIMS. Maiti and Bhowmick have also studied the effect of solution concentration (5, 10, 15, 20, and 25 wt%) on the properties of fluorocarbon clay nanocomposites [64]. They noticed that optimum properties are achieved at 20 wt% solution. At the optimized solution concentration, they also prepared rubber/clay nanocomposites by a solution mixing process using fluoroelastomer and different nanoclays (namely NA, 10A, 20A, and 30B) and the effect of these nanoclays on the mechanical properties of the nanocomposites has been reported, as shown in Table 4 [93]. [Pg.30]

Technology for preparing nanocomposites directly via compounding has been investigated by Vaia, Ishii, and Giannelis. Industrial R D efforts have focused on process technology (e.g., melt or monomer exfoliation processes), as there are a number of polymers (e.g., polyolefins) that do not lend themselves to a monomer process. Nanocomposites with a variety of polymers, including polyacrylates or methacrylates, polystyrene, styrene-butadiene rubber, epoxy, polyester, and polyurethane, are amenable to the monomer process. The enhancement of mechanical properties, gas permeability resistance, and heat endurance are the primary objectives for the application of PCN, and their success will establish PCNs as a major commercial product. [Pg.2311]


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See also in sourсe #XX -- [ Pg.307 ]




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