Rheology, layered-silicate polymer

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. 

Krishnamoorti R, Silva AS (2000) Rheological properties of polymer layered-silicate nanocomposites. In Pinnavaia TJ, Beall G (eds) Polymer nanocomposites. Wiley, New York Ren J, Silva AS, Krishnamoorti R (2000) Macromolecules 33 3739... 

Krishnamoorti R, Giannelis EP (1997) Rheology of end-tethered polymer layered silicate nanocomposites. Macromolecules 30 4097-4102... 

S. S. Ray, K. Yamada, M. Okamoto, and K. Ueda, New polylactide-layered silicate nanocomposites. 2. Concurrent improvements of material properties, biodegradability and melt rheology, Polymer 44, 857—866 (2003). 

Samyn, F., Bourbigot, S., Jama, C., Bellayer, S., Nazare, S., Hull, R., Castrovinci, A., and Camino, G. (2008) Crossed characterisation of polymer-layered silicate (PLS) nanocomposite morphology TEM, x-ray diffraction, rheology and solid-state nuclear magnetic resonance measurements, European Polymer Journal 44(6) 1642-1653. 

Rheology of various polymer layered-silicate nanocomposites - intercalated, exfoliated and end-tethered exfoliated (prepared by in-situ polymerization from reactive groups tethered to the silicate surface), have been performed in a conventional melt-state rheometer in both oscillatory and steady shear modes. These experimental studies have provided insight into the relaxation of polymer chains when confined by the layers of inorganic silicates, as well as the role of shear in orienting the layered nanocomposites. 

Kotsilkova, R., Rheology-structure relationship of polymer/layered silicate hybrids, Mech. Time-Depend. Mater., 6, 283-300 (2002). 

Krishnamoorti, R., and Yurekli, K., Rheology of polymer layered silicate nanocomposites, Curr. Opin. Colloid Interface Sci., 6, 464-470 (2001). 

Lee, S. H., Cho, E., and Youn, J. R., Rheological behavior of polypropylene/layered silicate nanocomposites prepared by melt compounding in shear and elongational flows, J. Appl. Polym. Sci, 103, 3506-3515 (2006). 

Lim, Y. T., and Park, O. O., Phase morphology and rheological behavior of polymer/layered silicate nanocomposites, Rheol. Acta, 40, 220-229 (2001). 

Koo, C. M., Kim, M. J., Choi, M. N., Kim, S. O., and Chung, I. J. 2003. Mechanical and rheological properties of the maleated p>olypropylene-layered silicate nanocomposites with different morphology. Journal cf Applied Polymer Science 88 1526-1535. 

Among the entire potential nanocomposite precursors, those based on layered silicates have been most widely researched probably because the starting clay materials are easily available and environmentally friendly, due to their low cost, and because their intercalation chemistry has been studied for a long time [25], Biopolymer-clay nanocomposites are a new type of materials, which are prepared by adding low amounts of clay (1-5%) to the biopolymer matrix [26]. Montmorillonite is the most commonly used natural clay and has been successfully applied in numerous nanocomposite systems [13], Some studies have reported amelioration of mechanical properties, thermal stability, water absorption, and electrical, rheological, and morphological properties of alginate films via the incorporation of nanoclay into polymer matrices [27],... 

X. K. Zhang, G. S. Yang, and J. P. Lin, Synthesis, rheology, and morphology of nylon-11/layered silicate nanocomposite. Journal of Polymer Science, Part B Polymer Physics, 44 (2006), 2161-72. 

Krishnamoorti R, Vaia RA (2001) Polymer nanocomposites introduction. In Vaia RA, Krishnamoorti R (eds) Polymer nanocomposites. ACS symposium series, vol 804, pp 1-5 Krishnamoorti R, Yurekli K (2001) Rheology of polymer layered silicate nanocomposites. Curr Opin Colloid Interface Sci 6 464-470... 

To conclude this section, the LDPE/LDH nanocomposites, like many poly-olefin/layered silicate-based nanocomposites, represent a highly inhomogeneous system with almost luiknown interactions between the LDH particles and the particles and polymer matrix. Therefore, the rheological analysis... 

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