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I
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
Vol. 9 , No. 3
REPORT OF THE JOINT RUBBER INSULATION COMMITTEE THE JOINT BUBBEB INSULATION COMMITTEE LIST OF MEMBEBS-la16
CONSUMERS’ CHEMISTS 8r ENGINEERS, AND CONSULTING CHEMISTS
W. A. Del Mar, Interborough Rapid Transit Co., New York. A. E. Ellis, Interborough Rapid Transit Co., New York. W. B. Geiser, New York Central R. R. Co., Collinwood, Ohio. E. W. Gundy, Pennsylvania R. R. Co., Altoona, Pa. H. B. Rodman, Binghamton, N. Y. J. B. Tuttle, Bureau of Standards, Department of Commerce, Washington, D. C. C. F. Woods, A. D. Little & Co., Boston, Mass. MANUFACTURERS
C. R. Boggs, Simplex Wire & Cable Co., Boston, Mass. W. S. Clark, General Electric Co., Schenectady, N. Y. G. d’Eustachio, Standard Underground Cable Co., Perth Amboy, N. J. C. W. Walker, American Steel & Wire Co., Worcester, Mass. E. L. Willson, Hazard Mfg. Co., New York. RESIGNED
P. Poetschke, Lederle Laboratories, New York. J. P. Millwood, Consulting Chemist. SECRETARY
W. A. Del Mar, 621 Broadway, Room 807, New York City.
.......*.. PABT I-GENERAL
REPORT
NEED OF SPECIFICATIONS
A demand for specifications which will enable purchasers of rubber insulation for wire or cable to secure good material on the basis of competitive bids has existed for many years. I n recent years, there has been no difficulty in securing insulation having the dielectric strength, specific resistance, elasticity and mechanical strength required in practice. Indeed, with the possible exception of dielectric strength these qualities are usually in excess of actual service requirements. There is another quality, namely, permanence, which although equally essential, has not been so easy t o obtain. While the physical properties of rubber insulation are susceptible of positive determination by tests which can be made before acceptance by the purchaser, the permanence of insulation can be ascertained with certainty only by actual trial, often a t great loss, inconvenience and even danger. It should, therefore, be the aim of specifications t o overcome this difficulty and by some indirect means, ensure that the manufacturers supply compounds having the required endurance. This obviously presents a d f i c u l t problem, as it requires that some relation be established between permanence and one or more of the properties which are susceptible of test. It has been established by experience that Hevea rubber or the rubber of the Hevea Brasiliensis tree, when properly cured, is a superior grade which is entirely satisfactory for electrical insulation of the class under consideration. Hevea rubber may, therefore, be specified with advantage, although certain other rubbers of good quality may be excluded. The rubber has t o be Hevea rubber of good quality, the materials associated with it in the compound must be known t o be non-deleterious and the compound itself must be well prepared, applied and vulcanized. TYPES OF SPECIFICATIONS
Two types of specifications have been devised t o compass those restrictions. The first type of specification proceeds on the assumption that certain physical characteristics are developed t o an unusual degree by the use of Hevea rubber, especially the grade known as fine Para. Among the qualities affected by the
grade of rubber, and alleged t o be useful indications of the presence of Para rubber, are the tensile strength, elasticity and specific electrical resistance. Accordingly some specifications have been issued in which one or more of these qualities is specified in an exaggerated degree. Experience has shown that such specifications are ineffective, as the specified physical quality can be obtained either by manipulation of poor compounds or a t the expense of permanence in compounds made originally of good materials. I n consequence of this, specifications based exclusively on physical tests have fallen into disrepute, but such tests now serve in modified form as adjuncts t o other types of specifications. The second type of specifications to be considered is that in which a more or less rigid formula for the compound is specified and compliance with it exacted either by inspection during manufacture, or by chemical analysis supplemented by other tests of the finished product. Inspection which will really ensure compliance with such specifications is usually impracticable. Reliance must, therefore, be placed principally upon chemical analysis. Three difficulties a t once arise. I n the first place, chemical analysis cannot directly ascertain the quality of the rubber which has been used in the manufacture of a compound; it can determine quality only by the indirect method of measuring certain characteristic constituents. It is, therefore, necessary to present in the specification a relation between the desired formula and the chemical findings. The second difficulty is that in the past, chemists have employed diverse methods of analysis which give inconsistent results. It is, therefore, necessary to establish a satisfactory and standard procedure for analysis. The method of analysis must not only yield the information desired, but it must also be practical and capable of yielding uniform results when applied t o the same compound by different chemists. I n order to secure this uniformity it is important t o describe the methods of analysis in detail. The third difficulty has been the non-uniform interpretation of analytical results. The specification hereinafter presented is of the second or chemical type, in which an endeavor has been made t o meet the three objections hitherto urged against such specifications. It contains a table showing the range of analytical results that should be obtained from a good compound containing 30 per cent of high class Hevea rubber, and is supplemented by a detailed analytical procedure. The specification is not complete as given, it being necessary t o add appropriate electrical and mechanical test requirements. Examples of complete rubber insulation specifications are cited in Part VI of this report. The specification should always be used in conjunction with the analytical procedure. The latter will, however, serve for the analysis of any compounds of the 30 per cent Para type with mineral fillers, provided the interpretation is made t o correspond. HISTORY OF THE COMMITTEE
The necessity of purchasing insulated wire under conditions of competitive bidding led the various departments of the government, the railroads and other large consumers, to issue specifications for rubber insulation. These specifications were based upon the individual experience or theories of a number of engineers, aided by suggestions from some of the manufacturers. For several years no attempt was made to standardize these specifications, and much trouble was given t o the manufacturers by the diversity of requirements contained in them. I n 1906, the Rubber Covered Wire Engineers’ Association, consisting of representatives of the leading manufacturers, prepared a specification which was offered as a standard. This was followed in 1911 by the revised specification of the National Board of Fire Underwriters, which, however, calls for a comparatively
Mar., 1917
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
low grade of compound. The former specification, although the best that could be agreed upon a t that date, was so defective as t o afford little or no protection t o consumers. The latter occupies a field by itself, and makes no pretension t o specifying the highest quality of compound. Consumers desiring highgrade insulation of great permanence, therefore, continued t o use their own specifications, altering them from time to time, in accordance with the best information available, with a growing tendency t o rely upon chemical rather than physical tests. Some difficulty was experienced both in obtaining bids and in enforcing these specifications owing t o the inability of chemists t o make concordant analyses of rubber compounds. This matter reached an acute stage in 1911,when a number of manufacturers and consumers held a conference in order t o discuss the possibility of standardizing specifications and analytical methods for rubber insulation. This conference was held a t New York on December 7, 1911,Col. Samuel Reber of the U. S. Signal Corps presiding. The following interests were represented : Signal Corps, U S. Army. General Electric Co. rlmerican Chemical Society. Hazard Manufacturing Co. Lederle Laboratories. Simplex Wire & Cable Co. New York Central Lines. Standard Underground Cable Pennsylvania R. R. Co. co. After a full discussion of the subject, a Committee was appointed to devise a specification and a n analytical procedure for rubber insulation, the Committee to report a t a future conference. The Chairman, assisted by other members, appointed the following t o serve upon this Committee which was named “The Joint Rubber Insulation Committee :” C. R. Boggs, Simplex Wire & Cable Co. W. S.Clark, General Electric Co. W. A. Del Mar, N. Y. Central R. R. Co. (later Interborough Rapid Transit Co.). W. B. Geiser, N. Y. Central R. R. Co. J. P. Millwood, Consulting Chemist. P. Poetschke, Lederle Laboratories. H. B. Rodman, Pennsylvania R. R. Co. Later a t the request of the Committee and by unanimous consent of the members of the original Conference, the following were added: J. B. Tuttle, U. S.Bureau of Standards. E. L. Willson, Hazard Manufacturing Co. W. A. Del Mar was elected secretary of both the Conference Committee and of the Joint Rubber Insulation Committee. No permanent chairman was elected, it being left to the Committee t o elect a chairman a t each meeting. The Committee immediately upon its formation decided t o confine itself t o the development of a specification and an analytical procedure for compounds of the 30 per cent Para type. I n accordance with this policy it made a study of the chemical characteristics of Hevea rubber and of the available analytical procedures. New procedures were also developed and studied. Samples of different rubber compounds were analyzed by these tentative methods. The results were unsatisfactory and the discrepancies were investigated. Subcommibtees were formed t o do much of this work. Twelve regular committee meetings, besides numerous sub-committee meetings, were held; many different compounds were distributed to be analyzed by the entire committee, and others were experimented upon by the sub-committees and individual members. After two years of this work the Committee presented a preliminary report to a Second conference which was held a t New York on October 15. 1913,Col. S. Reber again presiding. The report was unanimously accepted by the Conference and the Committee authorized to continue in existence for another year 2
The invitations were issued by Mr. E. B. Katte, Chief Engineer
of Electric Traction, of t h e Xew York Central Railroad Company.
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for the purpose of making any revisions that might appear necessary in its report, as the result of a year of experience with it. The Committee was also authorized to publish the preliminary report. This was accomplished through the courtesy of the American Chemical Society, the American Institute of Electrical Engineers, and the U. S. Bureau of Standards, the report appearing in their official publications, THIS JOURNAL (January, 1914),the Proceedings of the American Institute of Electrical Engineers (January, 1914),and Bureau of Standards Circular No. 38, respectively. Instead of reporting in a year. the Committee found it necessary to devote nearly 3 years t o this work, holding 13 additional meetings, or a total of 2 5 general meetings exclusive of subcommittee meetings. The Committee was authorized a t the second Conference, t o increase its personnel without securing the approval of the Conference Committee. It has added the following chemists t o its membership: A. E. Ellis, Interborough Rapid Transit Co., New York. G. d’Eustachio, Standard Underground Cable Co. E. W. Gundy, Pennsylvania R. R. Co. C. W. Walker, American Steel & Wire Co. C. F. Woods, A. D. Little Co., Inc., Bostoq. The following resignations have been accepted since the Second Conference: J. P. Millwood and P. Poetschke. Mr. Geiser also resigned, due to stress of other work, but has been reelected. The Joint Rubber Insulation Committee’s specification for rubber insulating compound has been adopted by the principal engineering societies which issue standards of the kind. Among these are the American Electric Railway (Engineering) Association, the Association of Railway Electrical Engineers and the American Society for Testing Materials. The specification has also been adopted by a large number of important purchasers of insulated wire, including the U. S. Signal Corps, the Panama Canal, the New York Central R. R. Co., the Interborough Rapid Transit Co., the Public Service Corporation of New Jersey, etc. The Committee desires t o express its thanks t o the many gentlemen not members, who have actively participated in the work, especially to Messrs. F. S. Deemer, F. A. Hull, M. M. Kahn, C. B. Martin, G. H. Savage, J. F. Tinsley and D. Whipple.
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PABT 11-SPECIFICATION FOB SO P E B CENT REVEA RUBBER COMPOUND (CHEMICAL CLAUSES)
I-A 30 per cent fine Para or best quality plantation Hevea rubber compound with mineral fillers, shall be furnished. It shall contain only the following ingredients: (I) Rubber; (2) Sulfur; (3) Inorganic mineral matter; (4)Refined solid paraffin or ceresine. 2-The vulcanized compound shall conform t o the following requirements, when tested by the procedure of the Joint Rubber Insulation Committee, results being expressed as percentages by weight of the whole sample: REQUIREMENTS INDEPENDENT OF THE AMOUNTOF RUBBERFOUND Maximum Minimum Rubber 33 30 Waxy Hydrocarbons 4 Free Sulfur.. 0.7 Red lead, carbon. or organic fillers shall not be present. REQUIREMENT^ DEPENDENT UPON AMOUNT OF RUBBERFOUND (Requirements for intermediate percentages shall he in proportion to the percentage of rubber found.) 30 PER CENT 33 PER CENT RUBBERCOMPOUND RUBBERCOMPOUND Maximum Minimum Maximum Minimum Saponifiable Acetone Extract 1.35 0.55 1.50 0.60 Unsaponifiable Resins 0.45 0.50 Chloroform Extract.. 0.90 .... 1.00 Alcoholic Potash Extract.. .. 0.55 .... 0.60 Total Sulfur (see note 2) . . . . 2.10 .... 2.30 Specific Gravity . . . . . . . . . . . . . . . 1.75 .... 1.67
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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y 3-The acetone solution shall not fluoresce. 4-The acetone extract (60 cc.) shall be not darker than a light straw color. j-Hydrocarbons shall be solid, waxy and not darker than a light brown. 6-Chloroform extract (60 cc.) shall be not darker than a straw color. 7-Failure t o meet any requirement of this specification will be considered sufficient cause for rejection. 8-Contamination of the compound, such as by the use of impregnated tapes, will not excuse the manufacturer from conforming t o this specification. NOTE I-This specification shall be supplemented by appropriate clauses relating t o tensile strength, elasticity, electric insulation resistance and dielectric strength. (See the Wire and Cable Specifications of the American Society for Testing Materials, the Association of Railway Electrical Engineers, etc., for examples of such clauses.) NOTE 2-The limit on total sulfur may be omitted a t the option of the purchaser. (See Part IV of this Report.)
Yol. 9, NO. 3
not more than 2 0 per cent will pass through a 40-mesh sieve. Sift all the material through a no-mesh sieve, regrinding what is retained on the sieve until the entire sample has passed through. The wires of the sieves shall be evenly spaced in both directions and shall be of 0.016 and 0.010 inch diameter in the 20- and 40-mesh sieves, respectively. Remove with a strong magnet any metal that may have come from the grinder and thoroughly mix the sample. EXTRACTION APPARATUS-The extraction apparatus shall conform with the accompanying Fig. 111. It shall be heated so that the period of filling an empty syphon cup with acetone and completely emptying it will be between z1/2 and 3'/2 minutes. PREPARATION OF REAGENTS: I-Acetone shall be freshly distilled over anhydrous potassium carbonate, using the fraction 56-57' C. n-Alcoholic potash solution shall be of normal strength and shall be made freshly by dissolving the proper amount of potassium hydrate (purified by alcohol) in 9 j per cent alcohol which has previously been distilled over potassium hydrate. The solution shall be allowed t o stand for 24 hours and only the clear liquid used. 3-Ether shall be washed with three successive portions of distilled water and distilled, using the fraction 34-36' C. 4-Chloroform shall be shaken with water, dried by calcium
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PART 111-ANALYTICAL PROCEDURE
OBJECT OF THE ANALYSIS-The
object of this procedure of analysis is t o determine whether rubber compounds comply Two 2 arm. S a m p / e s o f R u b b e r (-Mohe
Ace'fone Extract!ons)
I
I
Res;due:(Unii.ed) (SaponJfy
with
son) Res!duo
Sopont'f/ob/e €xtract
( T r e a t w / f h HCI C h e o f )
(Treat w l t h noand E t b e r )
1 Resj& dExu a l
Hydrocarbons. Unsaponifiab/e
8:
KO
Solution
Resins.
T o f a / Waxy Hydr ocar bons - A
frocf
., >lOTI\'E
POWER DEP:\RT-
IIEST, SEW TORK: Specification S o . 2 . S E W YORE; C E S T R A L R.\ILROAD CO., ELCCTRIC.XL DEPAKTXEST: Specification S o . 300. PASAIIA C.XSAL:Office oi General Purchasing .%gent, Circular S o . 1038. SIGS.IL
CORPS,
r.s. ARJIT:GencrA Specification S o . j81-Iz. ctc.
