Synthetic fibers Whiskers

Naturally occurring fibers such as cotton, cellulose, etc., have short whiskers protruding from the surface, which help to give a physical bond when mixed with rubber. Glass, nylon, polyester, and rayon have smooth surfaces and adhesion of these fibers to the rubber matrix is comparatively poor. In addition, these synthetic fibers have chemically unreactive surfaces, which must be treated to enable a bond to form with the mbber. In general, the fibers are dipped in adhesives in the latex form and this technology is the most common one used for continuous fibers. The adhesion between elastomers and fibers was discussed by Kubo [128]. Hisaki et al. [129] and Kubo [130] proposed a... 

Most minerals occur in a variety of morphologies. Although it is not exhaustive, the list we recorded as occurring in fibrous form (Appendix 1) contains more than 350 entries, each with a reference. The format follows that proposed in Dana s System of Mineralogy, (Palache, et al., 1944), one of the standard references in the field. The names of fibrous minerals are alphabetically arranged within each chemical group that is, elements, oxides, hydroxides, carbonates, sulfates, phosphates, and so on. A similar, parallel system has been adopted for the list of synthetic fibers (Appendix 2). The list of synthetics includes glassy fibers produced from natural materials, as well as whiskers. 

MMMF are synthetics that have crystalline rather than amorphous structures. Not surprizingly, early examples are reminiscent of the naturally occurring fibers synthetic chrysotile (lander and Wuhrer, 1938) and needles of amphibolelike composition and crystal structure (Shell et al., 1958). However, the bulk of the crystalline synthetic fibers, both in use and under investigation, do not have mineral equivalents therefore, we chose to use the term whiskers to distinguish crystalline man-made inorganic fibers from their natural relatives. 

This brief summary of the composition and structural characteristics of glass fibers, whiskers, and carbon and graphite fibers illustrates the ranges of synthetic inorganic fibrous materials. The purposes of the construction of these materials is to capitalize on the physical and chemical advantages of the fibrous morphology, size, and state. 

The large-production reinforcing agent used today is primarily glass. Other fibers include cotton, cellulosic fiber, sisal, polyamide, jute, carbon, graphite, boron, whiskers, steel, and other synthetic fibers.10 12> 289 291, 466 They all offer wide variations in composition, properties, fiber orientation/construction, weight, and cost (Tables 15.4 and 15.5... 

Sisal, and Whiskers, all of which see. Others sometimes used are chopped paper, macerated fabrics, synthetic fibers, and metal wires. To be effective, a reinforcement must form a strong adhesive bond with the matrix resin, to which end adhesion, promoting substances known as coupling agents are often preapplied to the fibers. Reinforcements differ from... 

Fibrous materials may be naturally occurring or synthetically manufactured by thermal or chemical processes (Fig. 1) (see Fibers, survey). Refractory fibers are generally used in industrial appHcations at temperatures between 1000°C and 2800°C. These fibers may be oxides or nonoxides, vitreous or polycrystalline, and may be produced as whiskers, continuous filaments, or loose wool products. 

The term s plastic, polymer, resin, elastomer, and reinforced plastic (RP) are some-what synonymous. However, polymer and resin usually denote the basic material. Whereas plastic pertains to polymers or resins containing additives, fillers, and/or reinforcements. Recognize that practically all materials worldwide contain some type of additive or ingredient. An elastomer is a rubberlike material (natural or synthetic). Reinforced plastics (also called composites although to be more accurate called plastic composites) are plastics with reinforcing additives, such as fibers and whiskers, added principally to increase the product s mechanical properties. 

The enhanced strength of whiskers and natural fibers, by comparison to the strength of materials of the same composition in another morphology, could be a coincidental in these crystalline synthetic and mineral fibers, a particular crystal direction is parallel to the direction of the applied stress. However, the inverse diameter-strength relationship indicates that factors other than crystal structure contribute to the mechanical strength of fibrous materials. 

Walker, J. S., and T. Zoltai (1979). A comparison of asbestos fibers with synthetic crystals known as whiskers. Ann. N.Y. Acad. Sci. 330 687-704. 

Whiskers are synthetic crystalline fibers of variable size, but with diameters of usually less than 25 microns. An upper limit in diameter exists because the physical and chemical properties approach those of the bulk material as the diameter of fibrous sample increases. Since the purpose of synthesis is to take advantage of some characteristic property of the material in fibrous form, such as enhanced strength for small volume, the optimum material has a small diameter. For similar reasons the aspect ratio of useful whiskers is often well over 100. Whiskers can be single crystals, but many are polycrystalline aggregates of fibrils with preferred orientations. The compositions and crystal structures of the compounds synthesized as crystalline fibers also have the broadest possible variety (Brenner, 1958). 

Scrolled-form fibers, eapillary whiskers, and the cage-framework zeolitic fibers offer not only large surface area, but sites for intrafibrillar reactions. These additional sites for adhesion are advantageous for special applications such as the use of fibers in filtration and in the eonstruction of composites. In faet, the synthetic composites most resemble bone, the tissue in which strength and resiliency are essential. It is not surprising that fibers will continue to be much used in our teehnologicaUy oriented society. 

Whisker, whisker-crystal A modern technical term originating in the field of solid-state physics for highly elongate crystals resembling mineral fibers that are synthesized from a variety of inorganic substances, usually at elevated temperatures or pressures. Whiskers are synthetic fibrous materials (see chapter 2). 

Use Monomer for acrylic and modacrylic fibers and high-strength whiskers ABS and acrylonitrile styrene copolymers nitrile rubber cyanoethylation of cotton synthetic soil blocks (acrylonitrile polymerized in wood pulp) organic synthesis adiponitrile grain fumigant monomer for a semiconductive polymer that can be used like inorganic oxide catalysts in dehydrogenation of tert-butanol to isobutylene and water. 

Potassium titanate whiskers were found to improve the tribological properties of NAO friction materials. These soft, synthetic refractory materials stabilize friction level, reduce pad wear, noise, fade, thermal conductivity, control porosity, and provide thermal reinforcement. Fibrous potassium titanates are being replaced by platelet and powder versions because of health concerns associated with respirable fibers. 

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