Asbestos did not always have the negative reputation that it does today. Today it is a substance that is feared throughout Chicago and the surrounding areas, talked about in the Chicago and suburban Chicago media, generally vilified, removed from our homes and buildings, and is considered a dangerous health risk by everyone. We even hire experts to remove it from our homes and the buildings that we work in. The book I'm reviewing today is from another era however, when asbestos was considered a positive material with many very important uses in our society. The book is called "Asbestos from Rock to Fabric" and was written by Charles Caroll-porczynski. The book goes through the processing of asbestos from start to finish. It talks about how to mine it, where to obtain it, how to process it, and how to transform it into various useful substances like fireproof cloth fireproof coatings, etc. I've included an excerpt from this book below which focuses mainly on the heat resistance properties of asbestos. This is one of the main reasons why espestice became so popular as a building material.
HEAT RESISTANCE
EFFECT OF HEAT ON STRENGTH OF ASBESOS FIBRES, YARNS AND FABRIC
Most asbestos products must possess good heat-resisting properties; therefore fibre selection should be based on the results indicating which variety withstands better the higher temperatures on exposure to constant and repeated heating
Table 10 shows the effect of heat on the tensile strength of chrysotile asbestos. The tensile strength values are based on breaking loads applied to fibre bundles measuring approximately 20 microns in cross section:
Table 10A
Effect of heat on tensile strength of Canadian chrysotile crude
Temperature
Tensile strength
Lb./sq.in
Per cent of original
Tensile strength
Normal
Heated 3 mins at 600° F
Heated 3 mins at 800° F.
Heated 3 mins at 1000° F.
Heated 3 mins at 1200° F.
131,000
120,000
96,000
78,000
42,000
100.0
91.6
73.3
59.5
32.0
Canad. Min. metal. Bull., 1951, April.
Table 10B
Effect of heat on tensile strength of various asbestos fibres exposed for one hour to 375̠̠° ± 10° C.
Original Strength
Kilometres
Per cent loss
In strength
Chrysotile asbestos:
A. Canadian 3F
B. Canadian 3F
C. Canadian 3K
D. Canadian 3K
E. Canadian Crude No. 1
F. Rhodesian (milled)
Crocidolite asbestos:
G. South African (milled)
20•8
16•8
26•9
15•1
51•0
35•3
39•6
35•8
24•0
15•0
12•0
18•5
21•5
64•2
Note: All samples were exposed to a standard atmosphere for 10 hours after heating and prior to testing for strength.
PHYSICAL AND CHEMICAL PROPERTIES OF ASBESTOS
It is evident from the graph that pure asbestos tape retains its original breaking strength over a wide temperature range.
The crocidolite tape shows a small increase in breaking strength, followed by a decrease which is more rapid than in the case of chrysotile asbestos.
It is fair however, to mention that most of the textiles made from chrysotile asbestos contain admixtures of organic or synthetic fibres, whilst those made from crocidolite are usually pure.
It may be noted that the underwriter’s grade of asbestos tape begins to lose strength as soon as heat is applied. This is due to the cotton content.
EFFECT OF HEAT ON THE BREAKING STRENGTH OF
COMMERCIAL ASBESTOS YARNS
Most asbestos yarns contain varying amounts of carrier fibres mainly cotton and viscose. The author has made several experiments in order to determine the relation of the percentage of organic fibres to the strength of the yarn exposed to high temperatures. Some results are represented by Fig. 9. This shows that 30 minutes exposure at 550°F. completely decomposes cellulose fibres, thus gratly reducing the strength of the yarn by minimizing twist binding force.
Obviously the more organic fibres there are in the mixture, the greater will be the degree of strength deterioration. After decomposition of the organic matter, the remaining strength of the yarn decreases slowly until a temperature of 900°F is reached, and decreases rapidly at higher temperatures. Examination of the cloth made from these yarns and exposed to the same conditions, gave from 10-25 per cent higher strength retention than that of the yarn alone, depending upon the weave and setting employed.
In order to give some idea of the temperatures which the various grades of asbestos textiles will safely stand, the following may be stated to be a general rule.
ASBESTOS
Analysis Table B, it may be noted that the original strength of fibres differs considerably from mine to mine. Losses in strength suggest that some fibres are more resistant to heat than others within the same variety (e.g., chrysotile). Abnormal loss in weight was observed in case of chrysotile A sample and this may account for its exceptionally high loss in strength on exposure to 375°C.
While most of the fibres exposed to the standard atmosphere Sample A regained approximately one third only. As might be expected, the greatest loss in strength occurred in crocidolite or blue asbestos. However the test on one sample only may not reflect the true value for the bulk of this variety of asbestos.
Perhaps the most reliable means of evaluating the strength of the fibres on exposure to heat is to test the textile products prepared from them.
PHYSICAL AND CHEMICAL PROPERTIES OF ASBESTOS FIBRES
There are, however, other factors in addition to asbestos content that may contribute to the performance at elevated temperatures.
For example:-
(a) Quality of raw material.
(b) Effectiveness of the opening and blending.
(c) Spinning and weaving techniques.
Generally, longer fibers, finer counts and closer settings tend to promote greater strength retention on exposure of the asbestos fabric to heat. Finally, especially severe conditions (flexing, abrasion), may reduce these limits and conversely, ideal conditions of service may greatly increase them.
adxasbestos removal.com 125 S Clark St Chicago, IL
HEAT RESISTANCE
EFFECT OF HEAT ON STRENGTH OF ASBESOS FIBRES, YARNS AND FABRIC
Most asbestos products must possess good heat-resisting properties; therefore fibre selection should be based on the results indicating which variety withstands better the higher temperatures on exposure to constant and repeated heating
Table 10 shows the effect of heat on the tensile strength of chrysotile asbestos. The tensile strength values are based on breaking loads applied to fibre bundles measuring approximately 20 microns in cross section:
Table 10A
Effect of heat on tensile strength of Canadian chrysotile crude
Temperature
Tensile strength
Lb./sq.in
Per cent of original
Tensile strength
Normal
Heated 3 mins at 600° F
Heated 3 mins at 800° F.
Heated 3 mins at 1000° F.
Heated 3 mins at 1200° F.
131,000
120,000
96,000
78,000
42,000
100.0
91.6
73.3
59.5
32.0
Canad. Min. metal. Bull., 1951, April.
Table 10B
Effect of heat on tensile strength of various asbestos fibres exposed for one hour to 375̠̠° ± 10° C.
Original Strength
Kilometres
Per cent loss
In strength
Chrysotile asbestos:
A. Canadian 3F
B. Canadian 3F
C. Canadian 3K
D. Canadian 3K
E. Canadian Crude No. 1
F. Rhodesian (milled)
Crocidolite asbestos:
G. South African (milled)
20•8
16•8
26•9
15•1
51•0
35•3
39•6
35•8
24•0
15•0
12•0
18•5
21•5
64•2
Note: All samples were exposed to a standard atmosphere for 10 hours after heating and prior to testing for strength.
PHYSICAL AND CHEMICAL PROPERTIES OF ASBESTOS
It is evident from the graph that pure asbestos tape retains its original breaking strength over a wide temperature range.
The crocidolite tape shows a small increase in breaking strength, followed by a decrease which is more rapid than in the case of chrysotile asbestos.
It is fair however, to mention that most of the textiles made from chrysotile asbestos contain admixtures of organic or synthetic fibres, whilst those made from crocidolite are usually pure.
It may be noted that the underwriter’s grade of asbestos tape begins to lose strength as soon as heat is applied. This is due to the cotton content.
EFFECT OF HEAT ON THE BREAKING STRENGTH OF
COMMERCIAL ASBESTOS YARNS
Most asbestos yarns contain varying amounts of carrier fibres mainly cotton and viscose. The author has made several experiments in order to determine the relation of the percentage of organic fibres to the strength of the yarn exposed to high temperatures. Some results are represented by Fig. 9. This shows that 30 minutes exposure at 550°F. completely decomposes cellulose fibres, thus gratly reducing the strength of the yarn by minimizing twist binding force.
Obviously the more organic fibres there are in the mixture, the greater will be the degree of strength deterioration. After decomposition of the organic matter, the remaining strength of the yarn decreases slowly until a temperature of 900°F is reached, and decreases rapidly at higher temperatures. Examination of the cloth made from these yarns and exposed to the same conditions, gave from 10-25 per cent higher strength retention than that of the yarn alone, depending upon the weave and setting employed.
In order to give some idea of the temperatures which the various grades of asbestos textiles will safely stand, the following may be stated to be a general rule.
ASBESTOS
Analysis Table B, it may be noted that the original strength of fibres differs considerably from mine to mine. Losses in strength suggest that some fibres are more resistant to heat than others within the same variety (e.g., chrysotile). Abnormal loss in weight was observed in case of chrysotile A sample and this may account for its exceptionally high loss in strength on exposure to 375°C.
While most of the fibres exposed to the standard atmosphere Sample A regained approximately one third only. As might be expected, the greatest loss in strength occurred in crocidolite or blue asbestos. However the test on one sample only may not reflect the true value for the bulk of this variety of asbestos.
Perhaps the most reliable means of evaluating the strength of the fibres on exposure to heat is to test the textile products prepared from them.
PHYSICAL AND CHEMICAL PROPERTIES OF ASBESTOS FIBRES
There are, however, other factors in addition to asbestos content that may contribute to the performance at elevated temperatures.
For example:-
(a) Quality of raw material.
(b) Effectiveness of the opening and blending.
(c) Spinning and weaving techniques.
Generally, longer fibers, finer counts and closer settings tend to promote greater strength retention on exposure of the asbestos fabric to heat. Finally, especially severe conditions (flexing, abrasion), may reduce these limits and conversely, ideal conditions of service may greatly increase them.
adxasbestos removal.com 125 S Clark St Chicago, IL
