Short-fiber asbestos

Asbest-aufschlkmmung, /. asbestos suspension -drahtnetz, n. asbestos wire gauze, -faser, /. asbestos fiber. -filz,m. asbestos felt. -flocken f.pl. asbestos flocks, asbestos wool, -gewebe, n. asbestos cloth, -handschuh, m. asbestos glove, -holz, n. asbestos lumber, -luftbad, n. asbestos air bath, -oUtb, n, short-fibered asbestos, -papier, n. asbestos paper, -pappe,/. asbestos board, -platte, /. asbestos plate or board, -schale, /. asbestos dish, -schicht, /. asbestos layer or bed. -schlefer, m. asbestos alate. -schirm, m. asbestos screen, -schnur, /, asbestos twine or cord, -schurz, m -schurze, /, asbestos apron. -woUe, /. asbestos wool. 

Short-fiber asbestos A trade name for asbestos with relatively short fibers. Both chrysotile and amphibole asbestos may occur in short fibers. 

Asbestos fiber identification can also be achieved through transmission or scanning electron microscopy (tern, sem) techniques which are especially usefiil with very short fibers, or with extremely small samples (see Microscopy). With appropriate peripheral instmmentation, these techniques can yield the elemental composition of the fibers using energy dispersive x-ray fluorescence, or the crystal stmcture from electron diffraction, selected area electron diffraction (saed). 

Table 12 Typical Properties of Anorin-38 Based Asbestos Short Fiber Reinforced Brake Linings...

To conclude this brief digression into history, we may point out one more important aspect the high efficiency of the combined shear in molding of filled thermoplastics. One of the first works in this field was 31) which described experiments carried out with polypropylene filled with a disperse aggregate calcium carbonate (chalk) and a short-fiber material-asbestos. 

As discussed in Section 3.4.4 inhaled asbestos fibers that are deposited in the lung are principally removed by mucociliary transport into the alimentary canal and eventually are excreted in the feces. Chrysotile fibers appear to be cleared more readily than amphibole fibers, and long fibers are cleared more slowly than short fibers (Coin et al. 1992 Morgan 1991). 

Goodglick LA, Kane AB. 1990. Cytotoxicity of long and short crocidolite asbestos fibers in vitro and in vivo. Cancer Res 50 5153-5163. 

Important determinations of asbestos toxicity include exposure concentration, duration, fiber dimensions, and fiber durability. There is animal and human evidence that long fibers are retained in the lungs for longer periods than short fibers and that amphibole fibers, such as tremolite asbestos, are retained longer than chrysotile fibers. Short and long fibers may contribute to the pathogenesis of inflammation, fibrosis, and cancer in humans, but their relative importance is uncertain. 

The different qualities (see Table 5.2-2) are reflected in asbestos fiber prices. In 1993 the longest fibers cost ca. 3800 DM/t compared with 4427 DM/t in 1979, whereas short fibers of Group 7 cost only 290 DM/t compared with 220 to 420 DM/t in 1979. 

Asbestos friction materials introduced in 1908 contained up to 65% of short chrysotile asbestos fibers that served as a cost-effective, heat-resistant, insulating reinforcement and friction enhancer. Asbestos formulations were widely employed in drum and disk formulations for several decades until health and safety concerns triggered efforts to find suitable substitutes. These materials are being universally phased out in favor of nonasbestos formulations. 

Asbestos Magnesium silicate Short fiber 2.56 — Gray 1.52... 

Aramid pulp is widely used as a substitute for asbestos. The aramid paper is used as insulating paper. In this case, mica, ground quartz, glass fibers, alumina, or talc, can be incorporated to improve the insulating properties. In contrast, if alumina laminae, carbon black, or stainless steel short fibers are incorporated, electrical conductive papers are obtained. Aramid paper is also used as a reinforcing agent in honeycombs. 

The recorded history of short fiber technology starts over two thousand years ago with asbestos fibers and reaches into the future with silicon nano-whiskers and carbon nanotubes. Asbestos is derived from the solid phase, but today, the most important short inorganic fibers are derived from the vapor phase. 

A discussion of applications of whiskers, short fibers, microtubes and nanotubes must start with a discussion of asbestos fibers. The blanket ban in the United States on all forms of asbestos was lifted by the Environmentai Protection Agency in 1991, but the legal climate is still complex. This holds true not only for asbestos and its composites [3] but also for all other needle-like fibers such as siiicon carbide whiskers and its composites when the whisker diameters are as low as <3 pm [57-58]. Pertinent governmental regulations [3] [57-58] need to be considered in the iarge-scale production, use or disposal of short needle-like fibers. 

Floats n. A term used in the past for asbestos filler in the form of very fine, short fibers with associated dust. 

Davis GS, Giancola MS, Costanza MC, Low RB (1982) Analyses of sequential bronchoalveolar lavage samples from healthy human volunteers. Am Rev Respir Dis 126 611-616 Davis JM, Addison J, Bolton RE, Donaldson K, Jones AD, Smith T (1986) The pathogenicity of long versus short fiber samples of amosite asbestos administered to rats by inhalation and intraperitoneal injection. Br J Exp Pathol 67 415-430... 

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