Polymer nanocomposites solvent blending

Morgan, A. B. and Harris, J. D. Exfoliated polystyrene-clay nanocomposites synthesized by solvent blending with sonication, Polymer (2004), 45, 8695-8703. 

Ma, J. Qi, Z. Hu, Y. (2001) Synthesis and characterization of polypropylene/day nanocomposites. J. Appl. Polym. Sci. Vol.82, No.l4, pp.3611-3617 Moniruzzaman, M. Winey, K. (2006) Polymer Nanocomposites Containing Carbon Nanotubes. Macromol. Vol.39, No.l6, pp. 5194-5205 Moore, D. Reynolds, R. (1997) X-Ray Diffraction and the Identification and Analysis of Clay Minerals (2nd edition). University Press, ISBN 0195087135, New York Ogata, N. Kaawakage, S. Ogihara, T. (1997) Poly(vinyl alcohol)-Clay and Poly(ethylene oxide)-Qay Blends Prepared Using Water as Solvent. /. Appl. Polym. Sci. Vol.66, No.3, pp.573-581... 

Styrene-butadiene copolymers are extremely important to the rubber industry. They are particularly important in tire manufacture. Styrene-butadiene polymer is produced by emulsion polymerization and solution polymerization. Most of the volume is by emulsion polymerization. This affords the opportunity to prepare polymer nanocomposites by several avenues. One can blend an aqueous dispersion of the nanoparticles with the styrene-butadiene latex before flocculation to produce the rubber crumb, disperse an organically treated nanoparticle in the styrene-butadiene solution polymer before the solvent is stripped from the polymer, disperse the organically treated nanoparticles into the monomers, or prepare the rubber nanocomposite in the traditional compounding approach. One finds all of these approaches in the literature. One also finds functional modifications of the styrene-butadiene polymer in the literature designed to improve the efficiency of the dispersion and interaction of the nanoparticles with the polymer. 

Solvent Blending Solvent blending for production of polymer-clay nanocomposites has been perceived as a process to be used only on a research scale, but in reality it may be more industrially friendly than the in situ process, at least for primary polymer producers rather than the downstream users. Although aspects of solvent blending are used in processing thermoset nanocomposites, this technique is really limited to thermoplastics or to polymers that can swell extensively in solvent, allowing polymer chains and clay to mix freely. 

The preparation of nanocomposites by melt intercalation is a very attractive environmentally friendly process since no solvent is required. In this method, the polymer matrix is blended in the molten state with a known amount of layered silicate. Under these conditions, if the layered surfaces are sufficiently compatible with the chosen matrix, the polymer can crawl into the interlayer space and forms an intercalated nanocomposite. In the case of poor compatibility between the silicate host and the polymer matrix, polymer intercalation is not allowed and micro-size clay particles are randomly dispersed in the matrix, forming a microcomposite. 

Melt state this method consists in mixing the clay directly with a molten polymer and then polymer inorganic nanocomposites are obtained by extrusion (Fig. 5). This process is not necessary to use solvent and is compatible with industrial polymer extrusion and blending processes, providing an economically viable route to obtain polymeric nanocomposites [15]. A wide variety of... 

Polymerization of vinyl monomers intercalating into the montmorillonite (MMT) clay was first reported in the literature as early as 1961. The most recent methods to prepare polymer-layered-siUcate nanocomposites have primarily been developed by several other groups. In general these methods (shown in Fig. 5.1) are able to achieve molecular-level incorporation of the layered silicate (e.g. montmorillonite clay or synthetic layered silicate) in the polymer matrix by addition of a modified silicate either to a polymerization reaction (in situ method), to a solvent-swollen polymer (solution blending), or to a polymer melt (melt blending). Recently, a method has been developed to prepare the layered silicate by polymerizing silicate precursors in the presence of a polymer. ... 

FIGURE 14.2 Illustration of in situ synthesis process of mixed-matrix nanocomposite membranes (a) metal ions are preloaded within polymer matrix to serve as nanoparticle precursor (b) monomers of polymer matrix and the nanofillers as the starting materials and (c) blending of the nanoparticle precursors and monomers of polymers in solvent. 

Recently, a continuous processing technique called solid-state shear pulverization has proven to yield polymer blends with compatibilized, sub-micron-size dispersed domains [6-8] as well as polymer nanocomposites with well-separated and highly dispersed nanofillers [9,10]. Its solid-state nature allows for morphology development to take place without regards to limitations in viscosity, thermodynamics and kinetics. It does not require heat, monomer, solvent, or chemical pre-modification, and thus is a practical and advantageous alternative for making effective polymer blends and nanocomposites. 

---