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The temperature properties of asbestos: this article describes the heat resistance of asbestos in various forms and notes the effects of high temperature on asbestos fibers, cloth, or other products.
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.
Temperature Properties of Asbestos Fabric or Cloth by Grade
As Rosato notes at ASBESTOS PROPERTIES, some forms of asbestos actually become stronger when subjected to high temperatures.
[Click to enlarge any image]
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.
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.
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
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.
In an effort to investigate the elevated temperature properties of some of the asbestos textile products and to make
comparisons between various grades and constructions, a
test set-up was adopted that had previously been developed
and used to determine the high temperature serviceability
of treated leather and some glass textiles.
The unit consists
of a Glo-bar heating element sop ositioned that a sample of
material to be tested can be placed in contact with it. The
material can be drawn or dragged over the heated Glo-bar while suspending a load of 2 lb. In this work, the samples
contacted the heating element four times per min for a duration of 7 1/2 sec over a 4-in. length.
The sample moved over
the heating element at a rate of 80 ft per hr. Abrasion occurs
during the test.
Shaw , M. C., Report No. 42, Sept., 1957, Report No. 44, March,
1958. Asbestos Textile Institute, Phila., Penna.
Fabrics composed wholly of glass have also been tested
on this machine; it has been found that such materials fail
immediately at 1,100°F. Upon making contact with the heat-
ing element at 1,100°F, the glass materials melt and the
sample tears apart.
Asbestos fabrics in grades from Underwriters through
AAA were studied. However, several other styles of chryso-
tile asbestos textiles were included, as well as samples of a
blue asbestos cloth in a style comparable to the standard
Tests performed on samples of blue asbestos revealed that
under the conditions of the test, this material proved to be
quite durable up to 1,500°F
however, at 1,600°F failure
was induced after 5
1/2 mm at 1,700°F failure was promoted
after one min; at 1,800°F failure occurred upon the second
contact or in approximately 10 sec.
Failure in the latter case
was caused primarily by melting; the abrasive action served
only in a minor degree to hasten destruction. Chrysotile data
are given in Table 2.8 fpimd below.
An asbestos textile
may be composed entirely of asbestos
fibers with varying amounts of an organic fiber, usually
cotton and rayon. The resistance to degradation by heat is
a function of the asbestos content and the
higher the asbestos content the higher will be its elevated
temperature serviceability characteristics.
of construction, weight and weave may also influence the ele
vated temperature properties and there should be an ap-
preciation of the potential influence of these factors if the
most efficacious adoption of an asbestos textile to a given
application is to be effected.
TABLE 2.8. GLO-BAR TEST ON ASBESTOS FABRIC (CHRYSOTILE)
Time in Mm, oF
* Review chapter on Textile for identification of grades.
! Shaw, M. S., Report No. 45, June 6, 1958. Asbestos Textile Insti-
tute, Philadelphia, Penna.
The generally accepted system of grading or classification
for asbestos textiles includes six grades ranging from 75 to
100 per cent asbestos content (see chapter on Textiles).
Manufacturing operations are such that as the asbestos
content is lowered and the cotton or other organic fiber content
is increased, it is possible to utilize asbestos fibers of a
shorter length than when there is a complete absence of or
only very small amounts of organic fiber present. The organic
fibers normally serve as a carrier fiber in the manufacturing
operation and contribute quite markedly to the
original strength of the textiles so formulated.
However, as the asbestos content of the cloth is increased
and the organic fiber content decreases, it becomes necessary
to utilize asbestos fibers of greater length. This action serves
to improve both the high temperature degradation resistance
characteristics and the strength properties over the entire
range of serviceability.
FIGURE 2.3 above describes the temperature properties of asbestos cloth or fabric of different grades. [Click to see an enlarged, detailed version of this or any image or table at InspectApedia.com]
Asbestos textiles are manufactured in a great many styles
and weaves, each being designed and manufactured to meet
specific application. Present day fabrics normally range
weights from 1.00 to 3.70 lb per sq yd in single cloth constructions.
FIGURE 2.4 above describes the hight temperature properties of asbestos cloth or fabricbased on temperature. [Click to see an enlarged, detailed version of this or any image or table at InspectApedia.com]
Asbestos yarns range from 8 to 35 cut; these are utilized
to provide several varieties of designs and weaves. The
varying . conditions of design and construction definitely
influence the physical properties and elevated temperature
characteristics of each type of cloth ; the extent of this influence
must be understood if there is to be a proper application
of these materials.
The elevated temperature serviceability characteristics of
wide variety of asbestos textiles have been determined as
function of the tensile strength retention properties ; this
information is set forth graphically in Figures 2.3 and 2.4.
Thermal Insulation Properties of Asbestos
There are some organic and inorganic materials which
can be classified as better insulating agents against heat
and electricity) than asbestos. However, in many instances,
these materials lack physical and chemical properties. Asbestos possesses a combination of different properties which
make ft particularly suitable for insulation.
TABLE 2.11. EMISSIVITY OF DIFFERENT MATERIALS
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Material Temperature, F Total Normal Emissivity
Shaw M C Asbestos Textile Institute Phila.,Penna.. (April 1951)
Organic fibers in cork may be strong and resistant enough for heat insulation,
but they are subject to oxidization and to thermal
decomposition. Magnesia, less sensitive against oxygen and
decomposition than cotton, has no inherent strength. Asbestos
combines these properties as well as others. In heat
insulation, it is important that numerous air cells or air
pockets exist. Asbestos provides for this type of structure.
Thermal reflectivity of materials is an important characteristic.
The ratio of heat radiated by a body to that of a
black body or the emissivity of asbestos is desirable for
insulation. In Table 2.11 [shown above] emissivity of various materials
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 Asbestos, its Industrial Applications, D.V. Roasato, engineering consultant, Newton MA, Reinhold Publishing Co., NY, 1959, Library of Congress Catalog No. 59-12535. We are in process of re-publishing this interesting text. Excerpts & adaptations are found in InspectApedia.com articles on asbestos history, production & visual identification in and on buildings.
 "Asbestos in Plastic Compositions", A.B. Cummins, Modern Plastics [un-dated, pre 1952]
 "Asbestos in Your Home," Spokane County Air Pollution Control Authority, Spokane WA 509-477-4727 www.scapa.org provides a one-page image, a .pdf file drawing of a house warning of some possible sources of asbestos in the home. The sources are not ranked according to actual risk of releasing hazardous levels of airborne asbestos fibers and the list is useful but incomplete.
 The US EPA provides a sample list of asbestos containing products epa.gov/earth1r6/6pd/asbestos/asbmatl.htm
 "Characterization of asbestos exposure among
automotive mechanics servicing and handling
asbestos-containing materials", Gary Scott Dotson, University of South Florida, 1 June 2006, web search 3/9/2012 original source: scholarcommons.usf.edu/cgi/viewcontent.cgi?article=3505&context=etd [copy on file as /hazmat/Automotive_Asbestos_Exposuret.pdf ].
 Asbestos Identification and Testing References
Asbestos Identification, Walter C.McCrone, McCrone Research Institute, Chicago, IL.1987 ISBN 0-904962-11-3. Dr. McCrone literally "wrote the book" on asbestos identification procedures which formed
the basis for current work by asbestos identification laboratories.
Stanton, .F., et al., National Bureau of Standards Special Publication 506: 143-151
Pott, F., Staub-Reinhalf Luft 38, 486-490 (1978) cited by McCrone
 ASBESTOS IN YOUR HOME U.S. EPA, Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
 Asbestos products and their history and use in various building materials such as asphalt and vinyl flooring includes discussion which draws on ASBESTOS, ITS INDUSTRIAL APPLICATIONS, ROSATO 1959, D.V. Rosato, engineering consultant, Newton, MA, Reinhold Publishing, 1959 Library of Congress Catalog Card No.: 59-12535 (out of print, text and images available at InspectAPedia.com).
 "Handling Asbestos-Containing roofing material - an update", Carl Good, NRCA Associate Executive Director, Professional Roofing, February 1992, p. 38-43
 EPA Guidance for Controlling Asbestos-Containing Materials in buildings, NIAST, National Institute on Abatement Sciences & Technology, [republishing EPA public documents] 1985 ed., Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460 Copy on file as ASBESTOS IN YOUR HOME - U.S. EPA, Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
Basic Information about Asbestos, US EPA, web search 08/17/2010, original source: http://www.epa.gov/asbestos/pubs/help.html
"Handling Asbestos-Containing roofing material - an update", Carl Good, NRCA Associate Executive Director, Professional Roofing, February 1992, p. 38-43
EPA Guidance for Controlling Asbestos-Containing Materials in buildings, NIAST, National Institute on Abatement Sciences & Technology, [republishing EPA public documents] 1985 ed., Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
Copy on file as ASBESTOS IN YOUR HOME - U.S. EPA, Exposure Evaluation Division, Office of Toxic Substances, Office of Pesticides and Toxic Substances, U.S. Environmental Protection Agency, Washington,D.C. 20460
[copy on file as /hazmat/Vermiculite_US_EPA.pdf/ Current Best Practices for Vermiculite Attic Insulation - May 2003, U.S. EPA
[copy on file as] /hazmat/Vermiculite_Health_Canada.pdf] Vermiculite Insulation Containing Amphibole Asbestos - September 2009, Health Canada
Managing Asbestos in Place, How to Develop and Maintain a Building Asbestos Operations and Maintenance (O&M) Program, U.S. EPA, web search 01/20/2011, original source: http://www.epa.gov/asbestos/pubs/management_in_place.html
Asbestos Strategies, Lessons Learned about Management and Use of Asbestos: Report of Findings and Recommendations on the Use and Management of Asbestos, 16 May 2003, US EPA, web search 01/20/2011, original source: http://www.epa.gov/asbestos/pubs/asbstrategiesrptgetf.pdf
prepared by the: Global Environment & Technology Foundation, 7010 Little River Turnpike, Suite. 460, Annandale VA 20003
Other US EPA Publications on asbestos: web search 01/20/2011, see http://www.epa.gov/asbestos/pubs/pubs.html
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