Platy minerals

Nonfibrous Reinforcements. Because of the higher costs associated with nonasbestos fibers and the performance requirements needed in replacing asbestos, platy minerals such as mica and talc, and metal powders such as iron and copper, are being used as a portion of the total reinforcement package in NAOs. 

De Sousa Santos, P., De Sousa Santos, H. and Brindley, G.W., 1966. Mineralogical studies of kaolinite-halloysite clays, 4. A platy mineral with structural swelling and shrinking characteristics. Am. Mineralogist, 51 1640-1648. 

Fibers are rolled around their long axis by gently tapping the cover slip with a dissection needle. Keep the fiber in view at all times as this is done. If a mineral plate is seen on edge it may resemble a fiber. Rolling the plate over reveals the true nature of the plate. This is a useful test when platy minerals such as talc or mica are being examined for the possible presence of asbestos. 

Many of the fine minerals shown previously in Figure 7 can be seen to be randomly oriented in fact, some of the platy minerals are found to be perpendicular to the layering. SAD experiments on some of the larger mineral plates typical of those shown in Figure 12 resulted in diffraction patterns of the type shown in the inset. The pattern was indexed as the (hkO) plane of kaolinite, indicating that the electron beam is parallel to the c-axis of the crystal. 

Platy minerals such as clays and talcs, are useful for providing stiffness to hot, semi-processed rubber products. This is particularly useful for thin-walled extrusions, which emerge from the die at high temperatures. The stiffening effect is usually sufficient to prevent collapse under the product s own weight immediately prior to and during cure. 

Fig. 5.70 Sections of a mica filled thermoplastic are shown in the optical (A and B) and TEM (C) micrographs. The platy mineral filler particles are aligned with the polymer. The particulate texture of the mica (black) in the TEM cross section reflects the effects of diamond knife fracture of individual mica flakes.

Luzenac America offers a broad selection of talc products designed specifically for plastic applications. Talc is a white, crystalline, platy mineral. It Is the softest of all minerals, and in many applications, its shape imparts cost-effective and beneficial structural properties to the final product. Luzenac talcs are available in various particle size distributions and from a wide variety of Luzenac-owned ore sources. 

Talc is a white, crystalline, platy mineral. It is the softest of all minerals. It must be mixed in the polymer melt to insure good dispersion. 

Wollastonite powder - This is milled wollastonite that has a low aspect ratio (3 1 - 5 1). It is produced fi om naturally low-aspect ratio ores and fi om high-aspect ratio ores that have been ground in a way that breaks the needles widthwise. Despite their relatively low aspect ratios, powder grades can provide better reinforcing properties than prismatic and even platy minerals in some applications. 

Kaolinite. Kaolinite is a leaf-like or platy mineral and is the major constituent of kaolin or china clay. Kaolin is used in the manufacture of paper products, plastics, rubber, ceramics, and refractory materials, and as a filler in paints. It is also found in inks, adhesives, insecticides, medicines, food additives, bleach, absorbents, cements, fertilizers, cosmetics, crayons, pencils, detergents, paste, floor tiles, and textiles. 

Vermieulite. Vermieulite is a platy mineral derived from biotite (aluminum magnesium silicate) that may be contaminated with fibrous mineral, such as tremolite. Vermieulite is expanded at high temperatures to form products for insulation and fireproofing and as a soil conditioner in horticulture. 

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