Asbestos types

Type II, fibrated lap cement (asbestos) Type III, fibrated lap cement (nonasbestos) Type I, nonfibrated... 

Optical microscope asbestos reference standards for use in identifying and quantifying asbestos types are available both from NIST and the Institute of Occupational Medicine flOM) in Edinburgh, Scotland. The lOM materials consists of various asbestos materials actinolite, amosite, anthophyUite, chrysotile (both from Cassiar, Canada and Zimbabwe), crocidolite and tremoUte. 

The NIST material SRM 1866a consists of a set of three common bulk mine-grade asbestos materials chrysotile, amosite and crocidolite, and one glass filter sample. SRM 1867 consists of a set of three imcommon mine-grade asbestos materials antophyllite, tremolite and actinohte. The optical properties of SRMs 1866a and 1867 have been characterized so that they may serve as primary calibration standards for the identification of asbestos types in building materials. 

The inorganic classification includes the metal pan type, consisting of a perforated metal pan with a sound-absorptive mineral wool pad the perforated cement-asbestos type, consiting of a perforated cement-asbestos sheet with a sound-absorptive mineral wool pad acoustical plasters and tile prepared from mixtures of inorganic or mineralized fibers with or without asbestos and other fillers. In general, acoustical products in this classification possess good fire and flame resistance, but are relatively expensive and difficult to manufacture and apply. 

Spiral wound gaskets cost about four to eight times more than compressed asbestos gaskets, but are easily worth it if they can prevent blowouts and leaks. Also, they generally last considerably longer than compressed asbestos-type gaskets. Spiral wound gaskets can be made in virtually any metal and filler... 

Asbestos type Species Median length ( j,m) Size distribution Carcinogenic effects Comments Conclusion Reference ... 

Dumortier P, Rey F. 1998. RE main asbestos type in pleural mesothelioma [Letter]. Am J Ind Med... 

Wagner JC, Berry G, Pooley FD. 1982a. Mesotheliomas and asbestos type in asbestos textile workers ... 

Polarized light microscopy is frequently used for determining the asbestos content of bulk samples of insulation or other building materials (see, for example, NIOSH Method 9002 [NIOSH 1989] and OSHA method ID-191 [OSHA 1994]). This method also enables qualitative identification of asbestos types using morphology, color, and refiactive index. 

Exposure to any asbestos type (i.e., serpentine or amphibole) can increase the likelihood of lung cancer, mesothelioma, and nonmalignant lung and pleural disorders. 

Are amphibole asbestos types more potent than chrysotile in inducing asbestosis and lung cancer ... 

Asbestos, the first inorganic fiber material used, is currently still exclusively produced from natural mineral deposits. It is formed by the hydrothermal conversion of basic and ultrabasic volcanic rock (olivine and pyroxene) to serpentine upon which the actual asbestos formation takes place leading to two asbestos sorts with different structures serpentine asbestos and amphibole asbestos. Asbestos can be produced synthetically by several hours heating of a polysilicic acid/metal oxide mixture (e.g. Mg, Fe, Co, Ni) in water at 300 to 350°C and 90 to 160 bar. The properties of four important asbestos types are summarized in Table 5.2-2. 

Table 5.2-2. Comparative Survey of the Properties of Four Important Asbestos Types,...

The macroscopic individual fibers of chrysotile asbestos consist of more or less parallelly oriented fibrils, which have a diameter of 15 to 40 nm and according to electron microscopic investigations are composed of carpet roll-like hollow fibers. The wall partitions of these small rolls consist of double layers of the composition Mg3(OH)4Si205, in which one brucite Mg(OH)2- and one Si205- layer are condensed with one another. These crystal lattices not fitting precisely with one another leads to curvature and hence a hollow fiber. Chrysotile asbestos is, as a result, easily fragmented into very fine fibers, which are soft and flexible and hence, of all the asbestos types, they lend themselves most easily to spinning. Industrially, however, chrysotile is always present as fiber bundles. 

Chrysotile is the asbestos-type most suitable for asbestos textiles. Only about 0.8% of the raw mtiterial is spinnable. In the manufacture of asbestos textile products, so-called carrier fibers (cotton or synthetic fibers) have to be added to achieve the required strength. These reduce the maximum operating temperature of the textiles from the ca. 480°C of yarn consisting of 99 to 1()09( asbe.stos, the temperature reduction being a function of the carrier fiber-content. Asbestos-free mineral fiber textiles arc generally used in the high temperature sector. 

At present, there is no official guidance defining what percentage of asbestos in soil would constitute a health risk and how this figure might depend upon the asbestos type, product, material, friability or moisture content etc. However, the UK HSE is also reviewing the test methods for asbestos materials in contaminated land and may provide additional guidance as part of this future documentation. 

TABLE 10.1 Asbestos Types and Their Chemical Compositions... 

Scanning electron microscopy (SEM) with an x-ray analyzer and transmission electron microscopy (TEM) are the most common techniques in electron microscopy. In the former technique, samples are scanned at 600 X and 2000 X and the metal ratios are quantitated from x-ray data. Element mass ratios, cation/anion ratios, and morphology are compared with empirical data from reference standards to identify the asbestos type. Air, water, and bulk samples may be analyzed by this technique. In blind tests, the correct identifications were made for more than 94% of fibers (Sherman et al. 1989). 

White asbestos (12001-29-5) refers to the degree to which the mineral surface achieves complete reflectance over the visible spectrum rather than to the actual colour or hue of the mineral consequently, white describes multiple asbestos types, although it is most commonly applied to actinolite, chrysotile, and sometimes anthophyllite and tremolite. Similarly, while brown asbestos principally refers to amosite, it actually describes the degree to which the mineral deviates from colourlessness toward yellow, tan, or brown. 

Quartz Glass fibre Polyamide Asbestos types... 

A low-power stereo binocular microscope is used to characterize and select suspected asbestos types fibers for further examination. Evaluation of the fibrous nature, color, luster, elasticity, flexibility, and other handling properties allows the detection and subsequent identification of asbestos in bulk materials at levels down to 10 mg kg... 

The primary variables [87,88] in depositing a diaphragm are the asbestos type and bath composition, rate of deposition, and baking, which are elaborated below. The guidelines discussed here are applicable with all the modifiers, although the precise values of the operating variables depend on the requirements at a given site. 

Asbestos Type. The primary source of chrysotile asbestos used worldwide is Zambezi asbestos. Zambezi fibers are mechanically processed and are soft with consistent length. Zambezi asbestos yields uniform diaphragms that are not prone to webs or bridging between the cathode fingers. However, they tend to form pinholes, especially on old cathodes. 

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