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Asbestos characteristics or properties:
This article series describes the physical properties of asbestos including its mechanical, chemical, electrical and related properties both in pure asbestos form and when asbestos is mixed with other materials like cement or rubber. As the author points out, while this is a lenghty article, there is far more detailed information about asbestos properties, chemistry, etc. A separate ASBESTOS BIBLIOGRAPHY gives access to much of that data.
Our articles about the properties, manufacture & uses of asbestos-containing products includes detailed information on the production methods, asbestos content, and the identity and use of asbestos-containing materials. Page top photo: tremolite asbestos in the forensic laboratory ©Daniel Friedman.
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The following text is Adapted from Rosato (1959) p. 37-611  © 2013 InspectApedia.com
The physical, mechanical, chemical, electrical, and related properties of asbestos without such added materials as Cement, rubber, etc., will be reviewed. However, it is important to appreciate that far more data for these afore-mentioned items are available. They are reviewed in the chapters listed at the end of this page - chapters which explain the properties of asbestos when it is combined with various other materials.
These data are directly related to the performance of products or end items; they are more important, inasmuch as more than 95 per cent of the asbestos used is combined with other materials. Some products are never identified as containing asbestos even when as much as fifty per cent of their content is asbestos, e.g., asphalt tile, vinyl tile, and plastics.
Basic properties of raw asbestos are interesting and important, but when the asbestos is combined with other materials, drastic differences may occur.
Physical and chemical properties of asbestos (as with many other materials) can be altered; e.g., heat resistance of asbestos fiber is a very important characteristic; it can produce more interesting results, however, when it is combined with other types of materials.
When asbestos fibers are subjected to a temperature of 1,200°F, their tensile strength values are extremely high. In comparison, tensile strength values of organic and inorganic fibers are completely destroyed or melt between 200 and 900°F.
Figure 2.2. View showing parallel fiber structure of asbestos vein, (Courtesy Johns-Manville-Corp.)
Ultimate tensile strength of chrysotile asbestos fibers is approximately 42,000 psi after two minutes at 1,2Q0°F ; 32 per cent strength retention occurs.
After one hour at 1,200°F, tensile strength drops to 2,000 psi. When the fibers are com- bined with silicone resin to produce structural plastics, the reinforced plastic can retain 50 per cent of its room temperature tensile strength or produce a minimum 10,000 psi after 5 to 10 hr. at 1,200°F.
With phenolic resins, asbestos products are produced which will provide insulation and retain strength when subjected to 5,000°F for periods of minutes (1 to 30 minutes) . See Figure 2.1 in which a rocket motor part is subjected to a temperature of 5,000°F. Figure 2.1. Rocket motor aft (asbestos-phenolic insulator) before and after firing at 5,000°F.
The temperature approximately 1/8 in. from the surface exposed to 5,000°F will be approximately 200°F after 1/2 to 1 min. of exposure.
When combined with magnesium carbonate and other similar products, heat insulators can be produced which will be useful for many years in such applications as boilers operating at temperatures from 500° to 1,200°F or 1,800°F. Although asbestos fiber mechanically breaks down at approximately 1,500°F, it does not completely disintegrate until 2,770°F. At this temperature, it can be related to such a ceramic material as magnesium oxide. When combined with other materials, it provides for interesting products in different temperature and time environments.
Asbestos is used with such binders as epoxy, furane and phenolic resins to produce chemical resistant products, otherwise immediate breakdown of the asbestos would occur. Typical applications include spinning bobbins for the manufacture of synthetic fibers, chemical corrosion re sistant asbestos-cement pipes, and chemical resistant plastic tanks.
Asbestos fibers can also be changed chemically to produce improved or completely different propertiès.*
Asbestos fiber or paper treated with a 20 per cent, by weight, of aqueous solution of magnesium chloride, dried, dipped in a 20 per cent aqueous solution of concentrated ammonium hydroxide, and dried at 175° F, causes an increase in strength ten times greater than its original strength. It also produces a 165 per cent increase in dielectric strength.
Reports on the various types of asbestos versus heat and chemical conditions have originated from various sources. In the majority of cases, specific data on physical or chemical properties of asbestos fibers have been obtained for use in special programs.
The method of conducting tests as well as conditions of evaluating data must be understood in order to obtain conclusive statements. In reviewing these data, it is important to recognize that specific conclusions can sometimes limit the application of the product.
For example, in the textile field ASTM Grade AAAA has been reported to have a service temperature as high as 900°F.
The ASTM Underwriters' Grade specifies service temperature as high as 450°F. These particular temperature values tend to be meaningless inasmuch as time periods are not included; therefore, their usefulness is limited.
See ASBESTOS TEMPERATURE PROPERTIES for more details about the effects of high temperatures on asbestos fibers & products.
Basically, asbestos is the only mineral which can be woven like cotton; it can resist fire, heat, time, weather and many 'acids or, alkalies. When it is used with other materials, its strong flexible fibers interlock to form .reinforcing webs within solids, liquids, and semiliquids.
The resulting products can gain durability and toughness as well as increased resistance to breakage, abrasion, and wear. The fibrous structure of an asbestos vein is shown in Figure 2.2 earlier on this page.
* Callinan, T. D. (to General Electric Co.) U.S. Patent 2,451,805 (Oct. 19, 1948).
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Web search 01/20/2011, original source: http://epa.gov/asbestos/pubs/verm_questions.html
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