December 1, 1916.] 



THE INDIA RUBBER WORLD 



149 



The Editor's Book Table. 



THE STABILITY OF VULCANIZED RUBBER AND THE OPTIMUM 

 Cure. By Henry P. Stevens, M.A., Ph.D., F.I.C, Reprinted (rom 

 "The Journal of the Society of Chemical Industry," London, England. 



THIS pamphlet, of value to every manufacturer of vulcanized 

 rubber, recapitulates the common knowledge of the sub- 

 ject, such as the danger of over-curing with consequent 

 hasty deterioration of the vulcanized product, the tendency to- 

 ward under-curing in order to prolong the life of the product 

 and the fact that this also causes gradual deterioration. The 

 methods of Schidrowitz and of Eaton and Grantham to deter- 

 mine the temperature, period of heating, etc., which will yield 

 the perfect or optimum cure are explained, and it is pointed out 

 that both methods fail to take into consideration the fact that 

 the tensile properties of a vulcanized rubber vary with the age 

 of the specimen. Figures obtained in any sort of tensile or 

 stretching tests will vary accordingly, inasmuch as vulcanization 

 appears to continue very slowly at the temperature of the air. 

 Thus Dr. Stevens concludes that any optimum cure method based 

 only upon load and elongation figures is valueless for technical 

 purposes ; rather that it should be based upon a correlation of 

 physical properties and aging tests. 



Then follows a corroboratory description of exhaustive experi- 

 ments with tabulated results, which were more fully referred to 

 in The India Rubber World, October 1, 1916. In studying 

 these it is particularly interesting to note that the crepe rubber 

 compounds cured for 3, SVa and 4 hours all show greater de- 

 terioration over any given period than the corresponding sheet 

 rubber compounds. This Dr. Stevens attributes to the method 

 of preparation. Whereas sheet rubber is merely squeezed after 

 coagulation and retains the original shape of the coagulated rub- 

 ber, crepe rubber is put several times through a washing mill 

 where it is torn up and ground in a stream of water. In his 

 experience, the extent to which rubber is worked previous to vul- 

 canization tends to reduce the life ©f the vulcanized product. 



THE FUNCTION OF LITHARGE IN THE VULCANIZATION OF 

 Rubber, Part II. By Henry P. Stevens, M.A., Ph D., F.I.C. Re- 

 printed from "The Journal of the Society of Chemical Industry," 

 London, England. 



Dr. Stevens here reviews and discusses the investigations which 

 have been made to determine the influence of the resinous constit- 

 uents. In 1912 Beadle and Stevens showed that the removal of 

 the greater part of the resins by acetone extraction retarded the 

 cure, impaired the tensile properties and increased the perishabil- 

 ity of the vulcanized product. L. E. Weber corroborated these 

 statements and even expressed the belief that ''the resins play an 

 active part in the vulcanization, and not merely as a catalyzer, 

 their presence being absolutely essential," in fact that the com- 

 pound prepared from resin-e.xtracted rubber "could not be vul- 

 canized," this latter statement being based upon the poor tensile 

 properties of the rubber. 



In the present pamphlet, however. Dr. Stevens maintains that 

 rubber may possess poor tensile properties and yet be vulcanized 

 to some extent or even over-vulcanized. He refers to his own 

 investigations to the effect that the degree of vulcanization is 

 largely dependent upon the relative proportions of rubber, sulphur 

 and litharge in the compound, and points out that the highly 

 specialized type of compound containing litharge which Weber 

 employed appears to be hardly suited to the purpose of ascer- 

 taining the specific vulcanizing properties of any particular rub- 

 ber sample. The fact that an essential criterion of a properly 

 cured rubber is its aging quality was also emphasized, any con- 

 clusion based upon the coefficient of vulcanization or upon phy- 

 sical tests with the freshly vulcanized specimen without taking 

 the aging quality into consideration being inaccurate. Then fol- 



lows a detailed account with considerable tabular matter descrip- 

 tive of an exhaustive series of tests pointing to the following 

 conclusions : 



Certain types of litharge compounds cannot be sufficiently 

 vulcanized to bring out their full tensile properties and co- 

 efficient of vulcanization without over-curing and consequent 

 deterioration or "perishing" with age. The removal of resinous 

 matter by acetone extraction retards vulcanization, as indicated 

 by the tensile properties and coefficient of vulcanization, particu- 

 larly with compounds containing litharge. It also reduces the 

 "stability" of the vulcanized compound, the effects of over-curing 

 being more marked than with untreated rubber. Throughout 

 the tests it was noticeable that plantation smoked sbeet rubber 

 vulcanized faster than the air dried (pale) sheet, although in 

 other respects both behaved similarly. 



EXPORTING TO LATIN AMERICA. BY ERNST B. FILSINGER. 

 D. Appleton & Co., New York City. [Large 8vo, 565 pages. 

 Price $3.] 



To the importer — whether of rubber or of any other com- 

 modity — and more particularly to the exporter, this book is 

 indispensable. It contains a vast fund of varied information 

 essential in making a success of exporting to our neighbor re- 

 publics to the southward. Written by a business man for busi- 

 ness men, it dispenses facts rather than theories, and provides 

 an intimate first-hand knowledge of the economic, social and 

 commercial situation of each South and Central American coun- 

 try that will enable manufacturers in the United States to deal 

 directly with their prospective customers. The resources, indus- 

 tries, needs and purchasing power of each are detailed; the 

 business methods and characteristics of the Latin people are 

 described, and former European export methods which have 

 pleased them are discussed. Considerable space is devoted to 

 tariffs, custom house regulations, packing, shipping routes and 

 facilities, local agents and publicity, while the appendix consti- 

 tutes in compact form a comprehensive encyclopedia of statis- 

 tical and descriptive information, including an extensive bibliog- 

 raphy of magazines, dictionaries, grammars and books devoted 

 to travel and the principal industries. Intelligent classification 

 and indexing makes any needed item available at a moment's 

 notice. 



Our readers will find this book of especial interest because 

 rubber and rubber goods are so frequently mentioned. The 

 author points out that although much of the crude rubber of the 

 world comes from Brazil and Peru, manufactured articles of 

 which rubber forms the basis are not produced in either coun- 

 try. As a consequence a splendid market exists for nearly 

 every line of rubber goods in demand in the United States, par- 

 ticularly rubber footwear, raincoats and other waterproof cloth- 

 ing adapted to the climate, druggists' sundries, rubber and woven 

 hose, tubing, sheeting and blankets, erasers, mats, life pre- 

 servers, etc. 



Manufactures are growing rapidly in South America and 

 natural resources are being developed so that much rubber belt- 

 ing and insulated wire are being used. The adoption of the 

 motor car in large cities for pleasure driving, parcel delivery 

 and even freight handling, together with the increased building 

 of improved country roads, are ever demanding more rubber 

 tires. Games and sports are being introduced which insure an 

 increasing need of tennis and golf balls, rubber-soled shoes and 

 the like. Indeed, the rubber manufacturer, in whatever line, 

 will find a considerable outlet for his product if he will but 

 study this market and approach it in the right way. Until the 

 war, Germany held a virtual monopoly of South American trade, 

 chiefly because she made it a point to give these merchants what 

 they wanted, carefully packed so as to arrive in perfect condi- 

 tion, prepaid to its destination and piloted through the custom 



