18 T O R R E Y A 



Between 1910 and 1941 much progress was made on the problems of 

 producing synthetic rubbers. Various sources of isoprene were investigated 

 and chloroprene, butadiene, and other compounds for use instead of isoprene 

 were developed. Facts were learned about the polymerization of these ma- 

 terials and co-polymerization with other hydrocarbons. 



The point to be understood is that synthetic rubber is no eleventh hour 

 miracle developed in response to the war emergency. The conditions imposed 

 by war have accelerated certain phases of synthetic rubber development, but 

 the underlying facts have been accumulated over a long period of time. 

 Knowing this, one is more inclined to appreciate the many difficulties that 

 have been involved in the manufacture of satisfactory synthetic rubber. 

 Monumental progress has been made toward overcoming these difficulties, 

 and in constructing and putting into operation plants for the production of 

 synthetic rubbers. The final answer has not yet been obtained. Hundreds of 

 chemists are working on the problems and continued improvement in quality 

 and usefulness may be expected. Up to the present, however, the production 

 of synthetic rubber has not alleviated the critical need for natural rubber. 



It is perhaps worth mentioning here that actually there is no such thing 

 as synthetic rubber. If there were there would probably be no need for natural 

 rubber. So-called synthetic rubbers are substances having some of the 

 essential physical properties of rubber, but none of the synthetics has the 

 chemical structure of rubber and none has all of its physical properties. There 

 are many types of synthetic elastomers or plastomers. A synthetic elastomer, 

 to be designated as synthetic rubber, must be a substance capable of vulcaniza- 

 tion and after vulcanization must stretch to at least four times its normal 

 length and then resume its original length forcibly and rapidly when the 

 pressure is released. GR-S, or the Buna type, synthetic has this property, but 

 in going through the procedure generates vastly more heat than natural 

 rubber. It is this factor which limits its use in tires where there is rapid 

 flexing. 



Large amounts of natural rubber are needed for combining with the 

 synthetics in the manufacture of larger size truck and bus tires. Many uses 

 still demand pure natural rubber. When these facts are considered in the 

 light of the daily growing demands for both military and civilian products 

 made of rubber, the necessity of increasing our supplies of natural rubber is 

 highlighted. 



Attempts to increase and assure our supply of natural rubber have been 

 three-fold and all were initiated in 1940. Agreements were made with several 

 of the Tropical American countries whereby the United States government 

 undertook, through an official agency, to guarantee the price of crude rubber 

 over a fairly long period — in most cases extending to 1946. This move was 

 aimed at stimulating: the collection of rubber from wild trees in Central and 



