It's 1915, and now the Germans are really in trouble. They are in the midst of the biggest war the world had ever seen with no rubber. The British will not let anyone sell rubber to the Germans, and every scrap of natural rubber has been reclaimed and recycled. German engineers have tried every substitute for rubber they can think of, and failed miserably. Germany is getting desperate!
Then, someone remembered about some pre-war trials in making synthetic rubber from 2,3-dimethylbutadiene, or methyl isoprene. Back in 1910, a pilot plant had been built to make methyl isoprene, which was used as the monomer for making methyl rubber. After initial testing, Dr. Carl Duisberg, director of Bayer, arranged to have a car fitted with tires made of methyl rubber which was presented to Kaiser Wilhelm II in 1912. After the car had been driven over 4000 miles without a tire puncture, which was quite a feat in the early days of automobiles, the Kaiser announced in June that he was "extremely satisfied" with the new driving experience, and ordered the entire fleet of automobiles to be fitted with methyl rubber tires. The "puncture proof" tires really were not as great as the Kaiser thought, however, because these tires were solid. That's right, no tubes, no air, just solid rubber. The tires could have had a pitchfork sticking out of the sidewall and they still would have been drivable!
Another problem with methyl rubber is it's propensity to degrade when exposed to oxygen. Methyl rubber would be great if it were to be used for tires on the lunar rover, but the space program was still a few decades off, and the Germans wanted to use their tires in the Earth's oxygen-rich atmosphere. So, after a few more tests, the chemists decided that methyl rubber was useless.
That is, until the desperate times of the Great War. A small amount of methyl rubber remained in the machines of the partially dismantled pilot plant, and after some testing, the methyl rubber is deemed to have sufficient properties to warrant large scale production. Anything is better than refaced old tire with melted jelly squirting out of them!
Now the Germans run up against another brick wall. The starting materials for making methyl isoprene are needed in other aspects of the war effort. Acetone is used in the manufacture of explosives, and aluminum is needed to build zeppelins and aircraft motors. Acetone can be made from wood or acetate of lime, but these supplies are quickly depleted. It can also be synthesized from acetic acid, the stuff that gives vinegar it's acidic flavor. Acetic acid, however, is the product of fermentation of grain or potatoes, but the troops on the battlefield and the civilians need to eat. The chemists are only allowed to use rotten potatoes, and that doesn't work well because the bacteria used for the fermentation is touchy. Finally, the industrious German chemists work out a roundabout procedure using lime and coal, two materials that are plentiful in Germany.
Now that they can make the monomer, they need to polymerize it to make the rubber. In these early days of polymer synthesis, any sort of polymerization takes several months to reach high conversion. Being in the midst of a war, the desperate chemists can not wait for the results of one reaction before starting another. After an enormous number of experiments, three methods are chosen.
If the methyl isoprene is allowed to stand in tin drums at 30oC (86oF) for six to ten weeks, H-rubber is formed. The "H" stands for the German word hart, or hard. This hard rubber is used for hard rubber goods such as submarine battery boxes, and cases for other electrical equipment, and is found to have more electrical resistance than hard rubber made from natural rubber latex.
If the methyl isoprene is placed in iron drums at 70oC (158oF) for three to six months, W-rubber is produced. The "W" stands for the German word weich, which, as you might guess, means soft. This is used for soft rubber goods such as belts, hoses, tires, and any other place you might want stretchy or flexible rubber. W-rubber, however, is far from satisfactory. It is difficult to vulcanize, and the crosslinked product is only elastic when warm. Solid tires made of the stuff are hard most of the year, and in the winter, large chunks will fall off of them when a car is started after staying in the cold overnight. Ideally, these vehicles would be placed in heated garages for the night. On the battlefield, however, cars have to be jacked up when left standing to prevent the tires from getting flat spots. At least this poor substitute for natural rubber tires is better than, wood, steel, and squirting melted jelly!
A third type of methyl rubber is formed by allowing the methyl isoprene to stand in contact with sodium wire in an atmosphere of carbon dioxide. This is B-rubber and it is used for insulating wires and coating balloon fabric.
By the end of the war, the Germans are producing about 150 tons of methyl rubber per month. A total of 2500 tons are produced in all, and factories are being built to increase production. As soon as the armistice is signed, however, production stops. The Germans know it is miserably inadequate, as does the rest of the world. It is just the best they had. The world has seen what chemists were capable of, and few are impressed. The plantation owners no longer tremble in fear at the word synthetic. But with British restrictions on rubber supply and the determination of the United States, Germany, and the Soviet Union, the synthetic rubber quest is far from over.
The development of methyl rubber is not exactly the high point of 1915. Here's something that is:
Einstein announces the general theory of relativity, which is a modification of Newton's theory of gravitation.
2. Herbert, Vernon and Attilio Bisio. Synthetic Rubber: A Project That Had to Succeed. Westport, Connecticut: Greenwood Press, 1985.
3. Howard, Frank A. Buna Rubber: The Birth of an Industry, D. van Nostrand Company, Inc., 1947.
4. Wolf, Howard and Ralph. Rubber: A Story of Glory and Greed. New York: Covici, Friede, 1936.