Organic spherical fillers

Spheres. HoUow spherical fillers have become extremely useflil for the plastics industry and others. A wide range of hoUow spherical fillers are currently available, including inorganic hoUow spheres made from glass, carbon, fly ash, alumina, and 2h conia and organic hoUow spheres made from epoxy, polystyrene, urea—formaldehyde, and phenol—formaldehyde. Although phenol—formaldehyde hoUow spheres are not the largest-volume product, they serve in some important appHcations and show potential for future use. 

Incompatibility problems with organic and inorganic spherical fillers in plastics may be overcome by grafting reactive groups on their surface or adding coupling agents. 

Several inorganic fillers/organic additives, such as silica, talc, kaolin, CaC03, titania, zeolites, cross-linked acrylic copolymers, spherical silicon beads, and so on, are employed in the plastics/coatings industry to attain the desired blocking performance. Some of these fillers are discussed elsewhere in this book in terms of their primary function only amorphous silica forms (natural and synthetic), used for antiblocking, will therefore be discussed in this chapter. 

In their function as fillers, the organic spheres share the performances and benefits of the spherical form, similar to glass and ceramic spheres. However, their effect on a polymer matrix is normally not the enhancement of mechanical strength, such as tensile strength and abrasion resistance. Instead, they can impart new features to thermoplastics and thermosets, such as reduced density, improved resilience and ductility, mechanical and thermal stress absorption, or enhanced thermal and electrical insulating properties. When added to binders and plastisols for coatings, the function of the spheres can be surface modification of the coated surface this may include the creation of a visual effect or antislip properties, or to make a protective coating [2, 3]. 

Spherical Particles Nanofiller with three dimensions in the nanometer regime are the spherical nanofillers obtained by sol-gel process [9, 10]. In sol-gel process the organic/inorganic hybrid material can be formed by the condensation reaction between the functionalized prepolymer and the metal alkoxides, leading to the formation of a chemical bond between the polymer and the inorganic filler. Therefore, the incorporation of filler particles in polymer through the sol-gel process avoids the aggregation of filler. 

Available fillers are of various types and forms, namely, rigid, flexible, spherical, ellipsoidal, flakes, platelets, fibers or whiskers. They may be organic or inorganic in nature. All varieties of fillers have been tried in polymers in order to impart various advantageous benefits. The presence of the fillers in ttie polymer matrix alters the rheological properties of the polymer. 

Recently, a spherical form of silica has been introduced by Elkem under the trade name Sidistar . This product has the right particle size distribution to serve as an impact modifier and may provide synergistic improvements with organic additives (Chapter 10). Blends with calcium carbonate and with high-aspect-ratio fillers should be of interest in rigid PVC. 

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