ApRii, 1, 1917.] 



THE INDIA RUBBER WORLD 



387 



What the Rubber Chemists Are Doing. 



JOINT RUBBEE INSULATION COMMITTEE'S SPECIFICATION FOR 30 PER results. Used in Connection with the analytic procedure the 



CENT HEVEA RtlBBER COMPOUND (CHEMICAL CLAUSES). .„•(;„.,.•„, ll ,„U} u ^ j j j 



specincation will enable purchasers to order a good compound 



THE following specilications and explanations are from the and to ascertain, with a greater certainty than heretofore, whether 

 report of the Joint Rubber Insulation Committee, pub- the material received represents the compound specified. 

 lished in full in "llie Journal of Industrial and Chemical The term Hevea applied to rubber means rubber from the 

 Engineering" (March, 1917). The analytic procedure was out- Hevea BrasiUeusis tree, whether wild or cultivated and regard- 

 lined in The India Rubber World (November 1, 1916). less of the locality in which it has been grown. Para rubber is 



Hevea rubber of the kind originally shipped from the port of 



SPECIFICATION . 



Para, Brazil, and comes in several grades. The rubber required 



1. A 30 per cent fine Para or best quality plantation Hevea ^y this specification should be Hevea rubber of good quality, 

 rubber compound with mmeral fillers shall be furnished. It ^^^h ^^ fi„(. p^^a or best quality plantation rubber. 



shall contain only the following ingredients: (1) rubber; (2) carbon is excluded, not only because it is considered, by some 



sulphur; (3) inorganic mineral matter; (4) refined sohd paraf- purchasers, to be deleterious, but because it interferes with the 



fin or ceresin. determination of rubber hydrocarbons. 



2. The vulcanized compound shall conform to the following r^^ jg^j -^ excluded because of the possibilities of its dele- 

 requirements, when tested by the procedure of the Joint Rubber terious effects on rubber 



Insulation Committee, results being expressed as percentages by Ozokerite is prohibited because the acetone extract obtainable 



weight of the whole sample. from it interferes with the separation of the acetone extract ob- 



REQUIREMENTS INDEPENDENT OF THE AMOUNT OF RUBBER tainable from the rubber, thereby vitiating the assay of the rub- 



FOUND. ber extract. This prohibition is unimportant to the manufactur- 



Maximum. Minimum. . i ■ i • -i. j • ,t • i ■ f 



„ , j^ J. ,, ,. ers, as ceresin, which is permitted, is the essential constituent of 



Waxy hydrocarbons 4 Ozokerite. 



reesiipiur .. j^^^ Upper limit is placed upon the rubber in order to prevent 



Red lead, carbon, or organic fillers shall not be present. j^e attainment of electrical and mechanical strength by the use 



REQUIREMENTS DEPENDENT UPON AMOUNT OF RUBBER "[ ^" ^'^""^ quantity of inferior rubber whose lasting qualities 



FOUND. might not be satisfactory. 



(Requirements for intermediate percentages shall be in proportion to the The hydrocarbons are limited, owing to their tendency tO sepa- 



percen ge o^ n^^ Cent"" 33 Per Cent. ^^^^ from the compound and thus cause porosity. 



Rubber Compoumd . Rubber Compoumd . The free sulphur is limited because an excessive amount may 



Maximum. Minimum. Maximum. Minimum. be deleterious.- 



Saponifiableacetoiie extract.. 1.35 0.55 1.50 0.60 xhe maximum limit on the saponifiable acetone extract is to 



Unsaponifiable resins 0.45 .... 0.50 .... , . , ,, 



Chloroform extract 0.90 1.00 .... prevent the usc of raw or reclaimed rubber with high saponifiable 



Ti'ta^silphunNou'")"::::: 2:" :;:: 2:30 :::: extract. The medium limit assists in forcing the use of //ez^^o 



Specific gravity 1.75 — 1.67 rubber, since it is characteristic of the acetone extract from 



3. The acetone solution shall not fluoresce. Hex'ca to be largely saponifiable. 



4. The acetone extract (60 cc.) shall be not darker than a The unsaponifiable resins are limited because a low proportion 

 light straw color. °f unsaponifiable resins is characteristic of Hevea rubber. A 



5. Hydrocarbons shall be solid, waxy and not darker than a high result might be due to the presence of reclaimed rubber, 

 light brown. The chloroform extract is limited, first to prevent the use of 



6. Chloroform extract (60 cc.) shall be not darker than a bituminous substances, and, second, to limit depolymerized and 

 straw color. under-cured rubber. 



7. Failure to meet any requirement of this specification will be The alcoholic potash extract is limited to prevent the use of 

 considered sufficient cause for rejection. saponifiable rubber substitutes. 



8. Contamination of the compound, such as by the use of The specific gravity is limited to reconcile the specification of 

 impregnated tapes, will not excuse the manufacturer from con- ingredients by weight with the practice of purchasing material by 

 forming to this specification. volume. 



Note 1. This specification shall be supplemented by appropriate Fluorescence of the acetone solution is prohibited, as it indi- 



clauses relating to tensile strength, elasticity, electric insulation cates the presence of bituminous substances, rosin oil or mineral 



resistance and dielectric strength. (See the Wire and Cable oils. 



Specifications of the American Society for Testing Materials, the The color of the acetone extracts is specified to conform with 



Association of Railway Electrical Engineers, etc., for examples the normal color of the extract of Hevea rubber, A darker 



of such clauses.) color indicates adulteration or an inferior grade of rubber. 



Note 2. The limit on total sulphur may be omitted at the The hydrocarbons are required to be solid in order to prevent 



option of the purchaser. the use of oils and paraffin of low melting point. The shade re- 

 quired is that obtained from paraffin wax or ceresin. Liquid 



EXPLANATION OF SPECIFICATION. hydrocarbons indicate reclaimed rubber softened with mineral 



Experience has shown that compounds of the grade which con- oil, or paraffin of low melting point, 



tains only good Hevea rubber, may be relied upon to be more The color of the chloroform extract is specified to conform 



permanent than those made of rubber of other grades. It is not with the color of dissolved gum in small quantities. The pres- 



affirmed by the committee that a compound which conforms with ence of bituminous substances would be indicated by a brown or 



this specification is necessarily permanent, or that a better com- black color. 



pound cannot be made, but it is believed that enforcement of the It would be desirable that the sulphur of vulcanization be 



specification will limit the use of inferior materials and that it limited to exclude reclaimed rubber, which contains the sulphur 



will put the manufacturers more nearly upon equality of en- of its previous vulcanization, but the committee has not yet de- 



deavor, where they can use their experience to obtain the best veloped an acceptable method for determining this quantit>. It 



