Montmorillonite agglomerate

Figure 1.7 Scanning electron micrograph of montmorillonite agglomerate (a natural cationic clay) prior to its dispersion into high aspect ratio nanoplatelets. 7000x. (Courtesy of Dr. S. Kim, Polymer Processing Institute.)...

Finely divided clay, often after drying and grinding to destroy natural agglomerates, is a common binder in tumble/growth agglomeration. One of the more common and best known is bentonite (Section 15.1), a montmorillonite (Al[Si205]0H). The most... 

A soil is essentially an agglomeration of mineral and organic matter, with pore spaces containing air, water, and nutrient solutions (73). Specific soils develop under the influence of five different factors parent material, climate, living organisms, topography, and time (74). The mineral portion of soils frequently includes clays such as montmorillonite and kaolinite, and crystalline minerals such as quartz, whereas the... 

Shearing forces vhll be required to break up agglomerates. The level of these shearing forces will depend upon the nature of the filler. For example, intense shearing is usually required when dispersing carbon black. Even more severe shearing will be needed to disperse montmorillonite clay into nanosized platelets. 

Table 6.1 includes typical quaternary ammonium salts used as organic modifiers in commercial montmorillonite nanoclays, which are to be primarily dispersed in nonpolar matrices. Figure 6.5 shows that hydrotalcite platelets of nanodimensions present a much smaller degree of agglomeration than the MMT particles. 

DMDHT-modified montmorillonite clay is supplied in an agglomerate form. The basic process involves drying and grinding the modified organoclay. Air classification is recommended to remove large particles in the milled products. A typical particle size distribution curve is shown in Figure 7.3. The mean particle size is normally in the range of 15-25 tim. Top size (99%) should be less than 60 trm. 

Absorption bands from stretching of silicon oxygen bonds (Si-0) occur in the region of 950-1100 cmThis is particularly important for layered clay-based bionanocomposites because Si-O bonds are present in clay. The absorption band for agglomerated clay layers (tactoids) is broad. The absorption band becomes narrower as the degree of exfoliation increases. Thus, FUR spectroscopy can be irsed to determine the extent of exfoliation in bio-nanocomposites (Klein et al., 2005). Absorption bands associated with different bonds of montmorillonite are shown in Table 1. 

Montmorillonite is usually modified with ammonium salts, in our study the selected ionic liquids were applied as modifying agents for the intercalation of montmorillonite. Surface properties of modified fillers, the zeta potential of suspended solids in the water, the oil absorption number, the impact of modifications on the tendency to agglomerate in the non-polar and polar medium were studied. 

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