Polystyrene polymer-clay nanocomposites

Fu, X.-A., and Qutubuddin, S., Polymer-clay nanocomposites exfohation of organophUic montmoriUonite nanolayers in polystyrene. Polymer, 42, 807-813 (2001). 

The addition of nanoparticles to synthetic rubber resulting in enhancement in thermal, stiffness and resistance to fracture is one of the most important phenomena in material science technology. The commonly used white filler in mbber industry are clay and silica. The polymer/clay nanocomposites offer enhanced thermo mechanical properties. Bourbigot et al. observed that the thermal stability of polystyrene (PS) is significandy increased in presence of nanoclay [75]. Thermal and mechanical properties of clays multiwalled carbon nanotubes reinforced ethylene vinyl acetate (EVA) prepared through melt blending showed synergistic effect in properties [76]. 

Figure 16.24 shows the schematic representation of dispersed clay particles in a polymer matrix. Conventionally dispersed clay has aggregated layers in face-to-face form. Intercalated clay composites have one or more layers of polymer inserted into the clay host gallery. Exfoliated polymer/clay nanocomposites have low clay content (lower than intercalated clay composites which have clay content -50%). It was found that 1 wt% exfoliated clay such as hectorite, montmorillonite, or fluorohectorite increases the tensile modulus of epoxy resin by 50-65%. Montmorillonite was used in a two stage process of nanocomposite formation. In the first step, montmorillonite was intercalated with vinyl monomer and then used in the second step to insert polystyrene by in situ polymerization. 

In this chapter, we shall deal mainly with montmorillonite (MMT) clay and with organo-clays and polymer/clay nanocomposites containing polystyrene (PS) as the matrix and incorporating MMT as the clay. 

Reference. [18] showed the strong infiuence of preparation route on the thermal properties of polystyrene (PS) nanocomposites. An appreciable reduction in Tg was observed only for composites obtained from solution, whereas the composites obtained by melt intercalation showed Tg values approximately equal to that of neat polymer. Some difficulties in detecting changes in Tg for polymer-clay nanocomposites occurring with the conventional DSC [19] method could be overcome using the TMDSC method. 

Several successful strategies are available in the literature [14] that increase the thermal stability of organic molecules. Full utilization of these strategies for the preparation of surface treatments of layered silicates with enhanced thermal stability for the development of polymer-clay nanocomposites has yet to be realized. An example of an effective strategy is the utilization of quaternary ammonium and phosphonium functional polystyrene as a surface treatment for montmorillonite that is employed to prepare polymer-clay nanocomposites [15]. TGA indicated a significant increase in the thermal stability of the organoclay and the polymer-clay nanocomposite. Imidazolium functional surface modifier for montmorillonite demonstrated a significant increase in the thermal stability of ABS terpolymer-clay nanocomposite when compared to the pure polymer and polymer-clay nanocomposites where the surface modification of the montmorillonite was produced with traditional quats [16]. These experiments were via TGA measurements. 

X. Fu, S. Qutubuddin (2001) Polymer-clay nanocomposites exfoliation of otgano-philic montmorillonite nanolayers in polystyrene. Polymer 42, 807. 

Nazarenko S, Meneghetti P, Juknon P, Olson BG, Qutubuddin S. Gas barrier of polystyrene montmorillonite clay nanocomposites effect of mineral layer aggregation. J Polym Sci B 2007 45(13) 1733-53. 

Akelah A, Moet A (1996) Polymer-clay nanocomposites free-radical grafting of polystyrene on to oiganophiUc montmorillonite interlayers. J Mater Sd 31 3589-3596... 

This book covers both fundamental and applied research associated with polymer-based nanocomposites, and presents possible directions for further development of high performanee nanocomposites. It has two main parts. Part I has 12 chapters which are entirely dedicated to those polymer nanocomposites containing layered silicates (clay) as an additive. Many thermoplastics, thermosets, and elastomers are included, such as polyamide (Chapter 1), polypropylene (Chapter 4), polystyrene (Chapter 5), poly(butylene terephthalate) (Chapter 9), poly(ethyl acrylate) (Chapter 6), epoxy resin (Chapter 2), biodegradable polymers (Chapter 3), water soluble polymers (Chapter 8), acrylate photopolymers (Chapter 7) and rubbers (Chapter 12). In addition to synthesis and structural characterisation of polymer/clay nanocomposites, their unique physical properties like flame retardancy (Chapter 10) and gas/liquid barrier (Chapter 11) properties are also discussed. Furthermore, the crystallisation behaviour of polymer/clay nanocomposites and the significance of chemical compatibility between a polymer and clay in affecting clay dispersion are also considered. 

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

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