Febrlaky 1, 1913. 



THE INDIA RUBBER WORLD 



233 



Commercial Possibilities of Synthetic Rubber. 



Dy Lothai- E. ll'ebcr, I'li.D. 



A PAPER READ AT THE THIRD INTERNATIONAL RUBBER 



CONFERENCE, HELD AT GRAND CENTRAL PALACE, 



NEW YORK. SEPT. 24 TO 30, 1912. 



IT is rather peculiar that although the conversion of isoprcne 

 into a ruhber-like siibstance has heen known for upwards of 

 twenty years, further progress in this direction has been 

 practically stagnant until recent date. This is rot altogether 

 due to lack of effort, but rather to the enormity of the problem. 

 The synthesis of rubber, however, received a new impetus about 

 three years ago w-hen two German chemists, Ilofmann and 

 Harries, working independently, succeeded in obtaining almost 

 simultaneously products which gave the chemical reactions of 

 rubber and had certain physical rcseml)lances to the natural 



Dr. Lothar E. Weber. 



product. Since then, considerable progress has been made in 

 this direction and, more recently, stock companies have been 

 formed and capital subscribed with a view to actually placing 

 synthetic rubber on the market. The daily press both in this 

 country and especially in Europe, gave this latest development 

 of synthetic rubber wide publicity, sharing the optimism of the 

 promoters and inventors of the new process, and as a result, 

 the general public and, to a very large extent, rubber manufac- 

 turers themselves, have been led to believe that synthetic rub- 

 ber can in the near future be manufactured in competition with 

 the natural product. 



T do not want to give the impression of holding in light re- 

 gard the magnificent work which has been accomplished by 

 European chemists in their efforts to synthesize rubber. I al- 

 most think that a certain amount of chemical training is neces- 

 sary to appreciate the innumerable difficulties and pitfalls which 

 face the investigator in these fields. These men deserve the 

 profoundcst admiration for their painstaking and laborious ef- 

 forts, but it is greatly to be deplored that the public was given 

 to understand that synthetic rubber is today a commercial possi- 

 bility, since, if the promise is not fulfilled, the attitude of the 

 public will scarcely be one of admiration. 



Synthetic rubber enthusiasts have been very fond of compar- 

 ing the synthesis of rubber with the synthesis of indigo, asserting 

 that the same fate awaits natural rubber that befell natural 



indigo. These two problems, however, have very little in com- 

 mon and differ from each other in such striking respects that 

 the two syntheses are not capable of comparison. I should like 

 to take up this comparison in more detail because I think in 

 this way the difficulties which will prevent commercial synthetic 

 rubber becoming a realization during the next few decades can 

 be more clearly shown. Before doing so. however, I would ask 

 your indulgence in attempting to make clear to those of you who 

 are not chemists, the meaning of a rather formidable looking 

 word which is always in evidence whenever there is any mention 

 of synthetic rublier. I refer to the word "polymerization." 



We are being continually informed that isoprene polymerizes 

 to rubber and that the process of converting isoprene into ru])ber 

 is one of polymerization. The process of polymerization briefly 

 stated, is one whereby a large number of small units combine to 

 make a single large unit. It is essentially a process of agglomer- 

 ation. This process of agglomeration takes place between the 

 molecules, the latter, as you know-, being regarded as the smallest 

 amount of substance that is capable of existence. The inolecules 

 of isoprene. at least 100 of them, unite and polymerize into one 

 single molecule of rubber. Unfortunately, we have not the least 

 idea exactly how many isoprene molecules go to make one 

 molecule of rubber, and it is probably certain that the natural 

 rubbers themselves vary very widely in the respect of their degree 

 of polymerization. It does, however, seem probable that the higher 

 the degree of polymerization ; that is to say. the more the num- 

 ber of isoprene molecules that unite to form one rubber molecule, 

 the l)ettcr are the physical properties of the rubber. In other 

 words, two rubbers of exactly the same chemical composition, 

 with different physical properties, owe this latter difference to 

 their different degrees of polymerization. It follows then, that 

 a uniform degree of polymerization would be the first require- 

 ment for a synthetic rubber. 



Unfortunately, the chemist of today is absolutely powerless in 

 determining this degree of polymerization experimentally and. 

 to a certain extent, of controlling it. For instance, it is not 

 possible to go into a laboratory with a quantity of isoprene and 

 polymerize the latter to any desired extent. In fact, we have 

 no means of feeling sure that we can on two different occasions 

 bring about the same degree of polymerization. With the chem- 

 ical methods available today it would be absolutely impossible 

 to make a product with an assured uriform degree of polymeriz- 

 ation, and until this is possible, I fail to see how there can be 

 any possibility of commercial synthetic rubber. The first re- 

 quirement of such a product is uniformity of polymerization, 

 InU as we have no means of determining this uniformity, or lack 

 of it, variations would be bound to occur which would make 

 the employment of such synthetic rubber by the manufacturer 

 altogether too precarious. We all know to what disagreeable 

 results variations in the uniformity of the natural product lead 

 and in the latter case the possibilities for uniformity are 

 infinitely more favorable than in the case of the synthetic product. 



Now let us briefly consider the case of indigo. Here the 

 problem was to manufacture an article of absolutely definite 

 characteristics and properties. It undoubtedly required a vast 

 amount of chemical skill before the composition of indigo was 

 determined, but once this important feat having been accomp- 

 lished, the chemist had a definite conception of the substance to 

 he synthesized. Furthermore, there could never be the least 

 doulit as to whether the investigator had actually succeeded or 

 not in obtaining indigo. It is the work of only a few moments 

 to be able to definitely decide whether a product is indigo or not. 



