Clay, compositions siliceous

Micro-composites are formed when the polymer chain is unable to intercalate into the silicate layer and therefore phase separated polymer/clay composites are formed. Their properties remain the same as the conventional micro-composites as shown in Figure 2(a). Intercalated nano-composite is obtained when the polymer chain is inserted between clay layers such that the interlayer spacing is expanded, but the layers still bear a well-defined spatial relationship to each other as shown in Figure 2(b). Exfoliated nano-composites are formed when the layers of the day have been completely separated and the individual layers are distributed throughout the organic matrix as shown in Figure 2(c). 

Clays are silicate minerals that may be platy or fibrous and are usually of exceedingly fine grain size, ranging from colloidal, a few nanometers in diameter, to a maximum of about a tenth of a micrometer. Similarly to other aluminosilicates, clays show considerable range in chemical composition with concomitant structural modifications (Fig. 2.13). A few of the clay minerals described as fibrous are briefly mentioned here. 

Clay-coal siliceous shale 48.0 ritic composition 148.0... 

It should be born in mind that this is a overall clay composition. When we compare the representations of a clay composition in both tables, we notice that chemists apply the existing nomenclature rules (chapter 3, Chemistry). Furthermore the above represention proves that clay contains a number of silicate minerals. The structure of these silicate minerals and of quartz was already discussed in the chapter on Geology and Minerology. In the next paragraph we will concentrate on a certain group of silicates, the so-called clay minerals. Without these minerals clay would not possess its specific clay properties. 

CAS 1332-58-7. A white-burning aluminum silicate that, due to its great purity, has a high fusion point and is the most refractory of all clays. Composition Mainly kaolinite (50% alumina, 55% silica, plus impurities and water). 

Deep-sea sediments cover more than 50% of the earth s surface and consist of carbonates, red clay and siliceous ooze (cf. Chap. 1). On average, red clay covers about 31% of the world s ocean basins but its abundance is much higher in the Pacific (49%) than in the Atlantic (26%) and Indian (25%) Oceans (Glasby 1991). Carbonates act as a diluent for the transition elements in deep-sea sediments because of the low contents of these elements in them and the composition of deep-sea sediments is therefore often presented on a carbonate-free basis. 

Figure 6.13 Structures of some clay and mica related minerals, formed from composite silicate-hydroxide layers...

Recently, Ahmadi et al. [320] prepared EPDM/clay nanocomposites with organoclay that was intercalated with MA-grafted EPDM (MA-g-EPDM) and EPDM-clay composites with pristine clay via indirect melt intercalation method. Authors characterized the dispersion of the silicate layers in the EPDM matrix by XRD and TEM analysis methods. They showed that the particles of organoclay were completely exfoliated in EPDM matrix, and the mechanical, thermal, and chemical properties of nanocomposites were significantly improved compared with conventional composites. 

The two decades have witnessed an extensive research and development in the field of thermoset nanocomposites. The physics and chemistry of intercalation of clay (layered silicate) in thermoset resin have been understood to a great extent though synthesis of fully exfoliated thermoset-based nanocomposites still remains as a challenge. More research is necessary to study the feasibility of integrating the nanoreinforced thermoset resins into the fibre-reinforced plastics to develop composite structure not... 

An alternative to in situ polymerization involves direct intercalation of macromolecules into layered structures. Silicates are most often used. The insertion of polymer molecules into layered host lattices is of interest from different points of view. First, this insertion process leads to the construction of organic-inorganic polylayered composites. Second, the intercalation physical chemistry by itself and the role intercalation plays in the gain of electronic conductivity are of interest. This becomes important in the construction of reversible electrodes " or when improving the physicomechanical properties of nylon-layered silicate nanocomposites, hybrid epoxide clay composites," and nanomaterials based on hectorite and polyaniline, polythiophene or polypyrrole. ... 

Nano-clay composites contain very thin, high aspect ratio, alumino-silicate platelets, derived from the stacks present in the parent clay. Two types of stmcture can be recognised, intercalated and delaminated. In the intercalated form, the stacks of platelets are still present, but with polymer chains present between clay platelets, pushing them apart. In the delaminated form, the original stacks are no longer present, and the platelets are fully dispersed. 

Carbonaceous Chondrites Type of stony meteorite, characterized by the presence of hydrated, clay-type silicate minerals and abnndant organic matter. They represent among the most primitive material known in the solar system, and are thought to approximate the bulk composition of the accreting solar nebula. 

In the case of rubber blend clay composites good state of exfoliation of the clay, sufficiendy strong filler-rubber interactions as well as the compatibility between different rubber phases are playing major role. The presence of intercalated organoclays restricts the mobility of the rubber chains due to their confinement between the layers. As the concentration of nano filler increases the loss modulus increased. This can be explained in terms of the friction between the filler particles and the rubber matrix when the filler particles are uniformly dispersed in the mbber matrix. The damping values are found to decrease with the amount of filler due to the restricted mobility of the polymer chains owing to the intercalation of polymer chains into the layers of silicates. 

Recently, the utility of inorganic nanoparticles as additives to enhance the polymer performance has been established. Various nano reinforcements currently being developed are nano-clay (layered silicates),cellulose nanowhiskers, ultra fine layered titanate, and carbon nanotubes. Carbon nanotubes, however, are the most promising of the new nanomaterials. Carbon nanotube-based polymer composites are poised to exhibit exceptional mechanical, thermal and electrical properties. ... 

The ineorporation of a few weight pereent of modified layered silieates whieh are properly dispersed in the mbber matrix ean result in very high surface areas for rubber-elay interactions, as compared to the conventional rubber-filler composites. According to the strength of the interfacial interactions between rubber matrix and layered silicate four type of rubber-clay composites can be produced ... 

---