Tactoids polymers

Ogata et al. (1997) first prepared PLA/ organoclay (OMMT) blends by dissolving the polymer in hot chloroform in the presence of dimethyl distearyl ammonium modified MMT (2Ci8MMT). XRD results show that the silicate layers forming the day could not be intercalated in the PLA/MMT blends, prepared by the solvent-cast method. Thus, the clay existed in the form of tactoids, consisting several stacked silicate monolayers. 

The addition of polymer has no effect on the phase transition temperature between the gel and tactoid phases of the clay system. 

FIGURE 8.23 Particles are formed from coacervates of crystallites that condense over tactoids and crystalloids to particulate floes. Upon aging the floes condense to dense agglomerates, but maintain the shape of the original crystallites. (From Heller, W., in Polymer Colloids II, R.M. Fitch, Ed., Plenum Press, New York, 1980. With permission of Elsevier Science.)... 

Conventional composites in conventional composites, the clay tactoids exist in their original aggregated states with no intercalation of the polymer matrix into the clay lamellae. 

The Eq. (55) was received for nanocomposites polymer/organoclay with oiganoclay intercalated structure and its application in the given case proves to be correct by organoclay packets (tactoids) (N > ) availability, that is a typical sign of Na -montmorillonite intercalated stmcture [56]. For nanocomposites PBT/MMT value is varied within the limits of 1.5-16.6 within the range of W=l lO mass. % [70]. 

Hence, the results stated above confirmed that the models, developed for the microcomposites rheology description, did not give melt viscosity adequate treatment for nanocomposites polymer/oiganoclay as well. And as earlier, the indieated nanoeomposites iheologieal properties deseription ean be obtained within the fiamewoik of a viseous liquid flow fractal model. Na -montmorillonite plates aggregation in paekets (tactoids) simultaneously reduces both melt viscosity and elasticity modulus in solid-phase state of nanocomposites. 

Li et al. [2003] postulated that the storage modulus of CPNCs, G, is a sum of three contributions these of the polymer matrix (G ), the confinement in the intercalated stacks (G c), and the interparticle frictional interactions between tactoids (G ) ... 

Smectic and nematic meso phases can be easily interconverted in the case of low-molar-mass compounds, and this gives melts of these compounds the characteristics of liquids. On the other hand, these melts are optically anisotropic because of their one-dimensional order, and so, have characteristic colors. Consequently, they are also known as liquid crystals. Solutions of rod-shaped macromolecules exhibit similar ordered behavior they are called tactoidal solutions. One-dimensional order can be induced in polymer melts by lowering the temperature below the melt or glass transition temperature, whereby the one-dimensional order is frozen in. The characteristic X-ray diagrams discussed above are then obtained. 

Figure 1.15 Schematic representation of formation of polymer-based CMP systems viz. (a) conventional bulk CMP (tactoid), (b) intercalated NCs, and(c) exfoliated NCs, via physical mixing (dry/solution phase mixing or melt compounding) and in-situ polymerization routes.

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