Interaction clay-solvent

The effect of polymer-filler interaction on solvent swelling and dynamic mechanical properties of the sol-gel-derived acrylic rubber (ACM)/silica, epoxi-dized natural rubber (ENR)/silica, and polyvinyl alcohol (PVA)/silica hybrid nanocomposites was described by Bandyopadhyay et al. [27]. Theoretical delineation of the reinforcing mechanism of polymer-layered silicate nanocomposites has been attempted by some authors while studying the micromechanics of the intercalated or exfoliated PNCs [28-31]. Wu et al. [32] verified the modulus reinforcement of rubber/clay nanocomposites using composite theories based on Guth, Halpin-Tsai, and the modified Halpin-Tsai equations. On introduction of a modulus reduction factor (MRF) for the platelet-like fillers, the predicted moduli were found to be closer to the experimental measurements. 

Choudhury et al. [86] have studied the effect of polymer-solvent and clay-solvent interaction on the mechanical properties of the HNBR/sepiolite nanocomposites. They chose nine different sets of solvent composition and found that chloroform/methyl ethyl ketone (Qi/MEK) (i.e., HNBR dissolved in Ch and sepio-lite dissolved in MEK) is the best solvent combination for improvement in mechanical properties. XRD, AFM, , and UV-vis spectroscopy studies show that the dispersion of clay is best in the Ch/MEK solvent combination and hence polymer-filler interaction is also the highest. images shown in Fig. 14a, b clearly elucidate the aforementioned phenomena. Consequently, the tensile strength and modulus are found to be higher (5.89 MPa and 1.50 MPa, respectively) for the Ch/MEK system due to the minimum difference in interaction parameter of HNBR-solvent (xab) and sepiolite-solvent (Xcd)- Choudhury et al. have also studied the effect of different nanoclays [NA, , 15A, and sepiolite (SP)] and nanosilica (Aerosil 300) on the mechanical properties of HNBR [36]. The tensile... 

Role of Polymer-Solvent and Clay-Solvent Interaction Parameters on the Morphology Development of Polymer-Based Nanocomposite... 

In order to understand the relationship between the difference in the interaction parameter of rubber-solvent (Xab) and clay-solvent (xcd) systems and the properties of HNBR/SP nanocomposites, the plots of modulus at 100% elongation and tensile strength versus Xab-Xcd are represented in Fig. 45a, b. An exponential decay in both modulus and tensile strength is observed with the increase in difference of interaction parameter. 7) and 7max follow the same trend as above. 

M. Maiti and A. K. Bhowmick, Effect of Polymer-Clay Interaction on Solvent Transport Behavior of Fluoroelastomer-Clay Nanocomposites and Prediction of Aspect Ratio of Nanoclay, Journal of Applied Polymer Science, 2007, 105, 435. 

Figure 2.6 Snaps of stacked platelets (each of size 16 ) after 10 time steps on 64 lattice with clay-solvent interaction e s = -2 (T= 1, left top, 7=5 right top), e = -1 (7= 1, left bottom), Ens = 1 ( =1) ight bottom). Solvent particle concentration is 0.2. (From Ref [36. )...

Figure 2.7 Transverse planar density (c/J of clay (filled) and solvent (open) particles versus x at T= 1-10 with clay-solvent interaction e s= 1, —1, -2 plates are in the...

Green, W.J., Lee, G.F., Jones, R.A., and Palit, T. Interaction of clay soils with water and organic solvents implications for the disposal of hazardous wastes. Environ. Sci. Technol, 17(5) 278-282, 1983. 

Solvent-polymer and solvent-clay interactions are very important in determining the morphology of polymer/clay nanocomposites. There are many reports describing the preparation of PNCs by solution mixing [65, 231-235]. Ho and Glinka [38]... 

It has been found that the HNBR/SP nanocomposite provides the best thermal and mechanical properties when HNBR is dissolved in Ch and SP is dispersed in MEK. XRD, AFM,TEM, and optical transmittance studies show that the dispersion of clay is best in the Ch/MEK solvent combination and, hence, polymer-filler interaction is also highest in this system. Thus, rather than implying that the solvent selection directly affects the physical properties of the nanocomposite, solvent acts on the properties through its influence on the developed morphology. 

It is well known that the lower the AGM value, the better is the rubber-filler interaction. As for the Ch/MEK solvent combination x is zero, hence the A CN, cp2X term of (27) is zero for such a solvent combination. In all other solvent combinations, where x 0. the A l N r tp2X term of (27) is positive. Thus, AGM of the system for the Ch/MEK solvent combination is the least, and dispersion (if clay is in the rubber matrix) is also best in this solvent combination, giving rise to the highest polymer-filler interaction. 

Microwave heating has proven to be of benefit particularly for reactions under dry media (e.g., solvent-free conditions) in open vessel systems (i.e., in the absence of a solvent, on solid support with or without catalysts) [4]. Reactions under dry conditions were originally developed in the late 1980 s [51], but solventless systems under microwave conditions offer several additional advantages. The absence of solvent reduces the risk of explosions when the reaction takes place in a closed vessel. Moreover, aprotic dipolar solvents with high boiling points are expensive and difficult to remove from the reaction mixtures. During microwave induction of reactions under dry conditions, the reactants adsorbed on the surface of alumina, silica gel, clay, and other mineral supports absorb microwaves whereas the support does not, and transmission of microwaves is not restricted. Moreover, microwaves can interact directly with reagents and, therefore, can more efficiently drive chemical reactions. The possible accelerations of such reactions are expected... 

Proteins contain a variety of functional groups that can bind them to mineral surfaces carbonyl, alcoholic, carboxylic acid, and amine. Studies have shown that protein adsorption to clays is rapid at a pH below the isoelectric point of the protein (e.g., McLaren, 1954 Armstrong and Chesters, 1964). Conversely, then, protein should be extracted by a solvent system with a pH above the protein s isoelectric point. There are also hydrophobic regions on some proteins that create the possibility for hydrophobic interactions between the sorbed protein and the mineral surface (Quiquampoix, 2000). 

Clays are aluminosilicates with a two-dimensional or layered structure including the common sheet 2 1 alumino- and magnesium- silicates (montmorillonite, hectorite, micas, vermiculites) (figure 7.4) and 1 1 minerals (kaolinites, chlorites). These materials swell in water and polar solvents, up to the point where there remains no mutual interaction between the clay sheets. After dehydration below 393 K, the clay can be restored in its original state, however dehydration at higher temperatures causes irreversible collapse of the structure in the sense that the clay platelets are electrostatically bonded by dehydrated cations and exhibit no adsorption. 

The first application we would like to discuss involves the analysis of thiofanox formulated on a clay carrier. Two specific questions for which FTIR provided answers were (1) are there interactions between the compound and the carrier material and (2) is the active ingredient completely removed by solvent extraction The answer to these questions required a comparison of spectra from the blank carrier and the formulated material before and after extraction. These spectra were obtained by thoroughly grinding each sample, mixing with KBr, and pressing... 

Figure 2.3a is purely a sketch. The exact interaction potential between n-butylammonium-substituted clay plates (or other charged colloidal particles) in solution must incorporate many effects, such as the size of the small ions and the molecular degrees of freedom of the solvent, that are beyond the scope of either the coulombic attraction theory or DLVO theory. However, whatever the complicated functional dependence, the curve must comprise two states of equal thermodynamic potential. Somehow, the valleys in VT, the total potential, must be of equal depth. As discussed previously, in Figure 2.3b we see that the DLVO theory can never account for this experimentally proved phenomenon. 

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