Layered silicate nanocomposites

Keywords Biodegradable nanocomposites, layered silicates, renewable resources, blends... 

Gilman, J. W., Harris, R. H., Shields, J. R., Kashiwagi, T., and Morgan, A. B. 2006. A study of the flammability reduction mechanism of polystyrene-layered silicate nanocomposite Layered silicate reinforced carbonaceous char. Polymers far Advanced Technologies 17 263-271. 

Montmorillonite, hectorite, and saponite are the most commonly used layered silicates for the preparation of nanocomposites. Layered silicates have two types of structure tetrahedral-substituted and octahedral-substituted. In the case of tetrahedrally-substituted layered silieates the negative charge is located on the surface of silicate layers, and henee, the polymer malrices can interact more readily with these than with oetahedrally-substituted material. 

Giannelis, E.P. 1996. Polymer layered silicate nanocomposites. Advanced Materials 8 29-35. 

Giannelis, E.P. 1998. Polymer- layered silicate nanocomposites synthesis, properties and applications. Applied Organometallic Chemistry 12 675-680. 

Homminga, D., Goderis, B., Hoffman, S., Reynaers, H. and Groeninckx, G. 2005. Influence of shear flow on the preparation of polymer layered silicate nanocomposites. Polymer 46 9941-9954. 

Ray, S.S. and Bousmina, M. 2005. Biodegradable polymers and their layered silicate nanocomposites In greening the 21 century materials world. Progress in Materials Science 50 962-1079. 

Ray, S.S. and Okamoto, M. 2003. Polymer/layered silicate nanocomposite a review from preparation to processing. Progress in Polymer Science 28 1539-1641. 

Sinha, R.S., Yamada, K., Okamoto, M. and Ueda, K. 2002. New polylactide/layered silicate nanocomposite A novel biodegradable material. Nano Betters 2 1093-1096. 

Xu, R., Manias, E., Snyder, A.J. and Runt, J. 2001. New biomedical poly(urethane uera)-layered silicate nanocomposites. Macromolecules 34 337-339. 

Zanetti, M., Camino, G., Thomann, R. and Mulhaupt, R. 2001. Synthesis and thermal behaviour of layered silicate-EVA nanocomposites. Polymer 42 4501- 4507. 

This mbber is very tacky in nature and contains acrylic group, which makes it polar in nature. Nanocomposites have been prepared based on this elastomer with a wide range of nanohllers. Layered silicates [53-55] have been used for this preparation. Sol-gel method [56,57], in situ polymerization [58], and nanocomposites based on different clays like bentonite [59] and mica [60] have been described. The mechanical, rheological, and morphological behaviors have been investigated thoroughly. 

Krishnamoorti, R., Vaia, R.A. and Giannelis, E. (1996) Structure and dynamics of polymer-layered silicate nanocomposites. Chemistry of Materials, 8, 1728-1734. 

Of particular interest are the recently developed nanocomposites consisting of a polymer and layered silicate because they often exhibit remarkably improved mechanical and other properties [3] when compared with pure polymer or conventional composites (both micro- and macro-composites). A primary progress in... 

Since the possibility of direct melt intercalation was first demonstrated [11], melt intercalation has become a method of preparation of the intercalated polymer/ layered silicate nanocomposites (PLSNCs). This process involves annealing, statically or under shear, a mixture of the polymer and organically modified layered fillers (OMLFs) above the softening point of the polymer. During annealing, the polymer chains diffused from the bulk polymer melt into the nano-galleries between the layered fillers. 

The rheological properties of insitu polymerized nanocomposites with end-tethered polymer chains were first described by Krisnamoorti and Giannelis [33]. The flow behavior of PCL- and Nylon 6-based nanocomposites differed extremely from that of the corresponding neat matrices, whereas the thermorheological properties of the nanocomposites were entirely determined by the behavior of the matrices [33]. The slope of G (co) and G"(co) versus flxco is much smaller than 2 and 1, respectively. Values of 2 and 1 are expected for linear mono-dispersed polymer melts, and the large deviation, especially in the presence of a very small amount of layered silicate loading, may be due to the formation of a network structure in the molten... 

Galgali and his colleagues [46] have also shown that the typical rheological response in nanocomposites arises from frictional interactions between the silicate layers and not from the immobilization of confined polymer chains between the silicate layers. They have also shown a dramatic decrease in the creep compliance for the PP-based nanocomposite with 9 wt% MMT. They showed a dramatic three orders of magnitude drop in the zero shear viscosity beyond the apparent yield stress, suggesting that the solid-like behavior in the quiescent state is a result of the percolated structure of the layered silicate. 

K. Okamoto and M. Okamoto also investigated the biodegradability of neat PBS before and after nanocomposite preparation with three different types of OMLF. They used alkylammonium or alkylphosphonium salts for the modification of pristine layered silicates, and these surfactants are toxic for microorganisms [56]. 

Okamoto, M. (2003) Polymer/Layered Silicate Nanocomposites , Rapra Review Report No 163, 166 pp Rapra Technology Ltd., London. 

Okamoto, M. (2006) Recent advances in polymer/layered silicate nanocomposites an overview from science to technology. Materials Science and Technology, 22 (7), 756-779. 

Ahmadi SJ, Huang YD, Li W (2004) Synthetic routes, properties and future applications of polymer-layered silicate nanocomposites. J Mater Sci 39 1919-1925... 

Laird DA, Barriuso E, Dowdy RH, Koskinen WC (1992) Adsorption of atrazine on smectites. Soil Sci Soc Am J 56 62-67 LeBaron PC, Wang Z, Pinnavaia TJ (1999) Polymer-layered silicate nanocomposites an overview. Appl Clay Sci 15 11-29 Lee J-F, Crum JR, Boyd SA (1989) Enhanced retention of organic contaminants by soil exchanged with organic cations. Environ Sci Technol 23 1365-1372 Lee J-F, Mortland MM, Boyd SA, Chiou CT (1989a) Shape-selective adsorption of aromatic molecules from water by tetramethylammonium-smectite. J Chem Soc Faraday Trans I 8 2953-2962... 

Layered silicates, in nylon-clay nanocomposites, 77 313 Layer-lattice solids, 75 246 Layers, in landfill design, 25 878-879 Lazurite, 79 406... 

Analysis of Thermoset Materials, Precursors and Products, Martin J. Forrest, Rapra Technology Ltd. Polymer/Layered Silicate Nanocomposites, Masami Okamoto, Toyota Technological Institute. 

M. Alexandre, P. Dubois, Polymer-layered silicate nanocomposites Preparation, properties and uses of a new class of materials, Materials Science and Engineering, vol. 28, pp. 1-63, 2000. 

P. C. LeBaron, Z. Wang, T. J. Pinnavaia, Polymer-layered silicate nanocomposites An overview, Applied Clay Science, vol. 15, pp. 11-29,1999. 

The most-popular nanofiller is a natural layered silicate, montmorillonite, that is subjected to specific treatments. The properties of the final nanocomposite depend on the these treatments and the mixing efficiency. 

Pol Tner Nanocomposites are novel plastic compounds with a filler having dimensions between 1 and 100 nm. They have attracted much attention in the past because nanocomposites exhibit markedly improved properties like stiffness, thermal flammability, improved barrier properties and others compared to the unfilled matrices [3], Among all potential fillers, those based on easily available clay and layered silicates have been more widely investigated for some time now. 

---