Clay, as extender

McGuffog, Clays as Extenders in Decorative Paints. ECCInternational. 

Figure 19.11. Contrast ratio vs. percentage PVC. Courtesy of ECC International, St Austell, UK in McGuffog R M, Clays as Extenders in Decorative Paints. ECC International.

Polymers are often used in conjunction with other materials as composites. The most familiar types are the fiber-filled composites such as fiberglass and the carbon-, boron-, or Kevlar-filled advanced composites. Granular-filled composites such as those using clay as extenders in some plastics or ground quartz added to dental plastics to increase their wear resistance also represent an important class of materials. In these cases the presence of a second phase as well as the interface between polymer and filler increases the complexity of the failure analysis. 

Extenders are generally classified as such because they are low in cost compared to the polymer into which they are incorporated. A preferred term for clays used as extenders might be functional fillers because addition to a polymer almost always alters its properties to some extent (15). 

We have shown that the determination of vinyl silane on aluminum hydroxide powders is comparable to similar analyses on kaolin clays as reported earlier [2] and suggest with confidence that this technique can be extended to other powder substrate systems with sufficiently small particle sizes, i.e. comparable or less than the wavelength of the analytical frequency radiation as well as to the various other silanes that have been deposited on other substrates. 

Fillers are relatively nonadhesive substances added to the adhesive formulation to improve its working properties, strength, permanence, or other qualities. The improvements resulting from the use of fillers are listed in Table 1.8. Fillers are also used to reduce material cost. By selective use of fillers, the properties of an adhesive can be changed significantly. Thermal expansion, electrical and thermal conduction, shrinkage, viscosity, and thermal resistance are only a few properties that can be modified by the use of fillers. Common fillers are wood flour, silica, alumina, titanium oxide, metal powders, china clay and earth, slate dust, and glass fibers. Some fillers may act as extenders. 

Surface analytical techniques. A variety of spectroscopic methods have been used to characterize the nature of adsorbed species at the solid-water interface in natural and experimental systems (Brown et al, 1999). Surface spectroscopy techniques such as extended X-ray absorption fine structure spectroscopy (EXAFS) and attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) have been used to characterize complexes of fission products, thorium, uranium, plutonium, and uranium sorbed onto silicates, goethite, clays, and microbes (Chisholm-Brause et al, 1992, 1994 Dent et al, 1992 Combes et al, 1992 Bargar et al, 2000 Brown and Sturchio, 2002). A recent overview of the theory and applications of synchrotron radiation to the analysis of the surfaces of soils, amorphous materials, rocks, and organic matter in low-temperature geochemistry and environmental science can be found in Fenter et al (2002). 

Micas. If the double-chain amphibole structure diagrammed in Figure 2.8a is extended in two dimensions by the bonding of all three basal 0 atoms of each tetrahedron with Si atoms of other tetrahedra, a sheet silicate (phyllosilicate) is formed with the structure shown in Figure 2.9a. This polymer, extended infinitely in two dimensions, has the formula (Si40to) and is the basis of the mica structure (as well as the layer silicate clays, as will be discussed later in this chapter). 

The reinforcement of polypropylene and other thermoplastics with inorganic particles such as talc and glass is a common method of material property enhancement. Polymer clay nanocomposites extend this strategy to the nanoscale. The anisometric shape and approximately 1 nm width of the clay platelets dramatically increase the amount of interfacial contact between the clay and the polymer matrix. Thus the clay surface can mediate changes in matrix polymer conformation, crystal structure, and crystal morphology through interfacial mechanisms that are absent in classical polymer composite materials. For these reasons, it is believed that nanocomposite materials with the clay platelets dispersed as isolated, exfoliated platelets are optimal for end-use properties. 

Nonreinforcing fillers include calcium carbonate, clays, silicates, and alumi-nates. They are primarily used as extending fillers that is, they serve the purpose... 

Monsanto, until recently, produced high-molecular-weight vinyl acetate-MA materials as part of their Lytron resin series. These materials have been investigated as extenders for bentonite mud and as flocculants for drilling clays (Table The high carboxyl content and water solubility... 

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