How Did Artificial Rubber Come About?
Curious about how the artificial rubber materials that make up our erasers and eraser tips came about? We take a deep dive into the history of this fascinating material.
The successful solution of the problem of industrial synthesis of rubber is one of the most significant achievements of science and technology of the 20th century, because industry needs clearly exceeded the natural ability to produce rubber rubber plants. The synthesis of rubber on a large factory scale for the first time in the world was carried out in 1932 in the USSR according to the method developed by S. V. Lebedev. In 1938, industrial production of styrene-butadiene rubbers in Germany was organized, in 1942 – large-scale production of synthetic rubbers in the United States. By 1972, synthetic rubbers were produced in more than 20 countries.
In the development of rubber synthesis S.V. Lebedev followed the path of imitation of nature. Since natural rubber is a polymer of a diene hydrocarbon, S.V. Lebedev also used a diene hydrocarbon, only a simpler and more accessible one — butadiene. Ethanol was used as raw material for butadiene. However, the obtained synthetic rubbers, surpassing the natural in individual indicators, were inferior to it in one property – elasticity. Meanwhile, this property is fundamental in the manufacture of products such as automobile and aircraft tires that experience multiple deformations during movement.
Further studies have shown that natural rubber has a stereoregular structure, the -CH2- groups in rubber macromolecules are not randomly located, but on the same side of the double bond in each link, i.e. are in cis position. Such an arrangement of the -CH2- groups, through which the links in the macromolecule are connected, contributes to its natural twisting into a ball, which causes the high elasticity of the rubber. In the case of trans-structure of the links, the macromolecules are more elongated and do not possess such elasticity. In the synthesis conditions, the stereoregular structure did not work, which affected the properties of the polymer. But the problem was still solved thanks to the catalyst (metallic sodium), which provides stereoregular stacking in the growing polymer chain. As a result, rubber is created according to properties similar to natural; It has good water and gas impermeability. To increase strength and elasticity, it, like natural rubber, is subjected to vulcanization.
The widespread use of butadiene rubber for the production of a variety of rubber products has led to major changes in the raw material base of rubber production. At the time of the synthesis of synthetic rubber, S. Lebedev used ethanol as a raw material for butadiene, and grain and potatoes were used to produce it. The interests of the economy demanded more accessible sources of raw materials, therefore, at present, hydrocarbons contained in petroleum gases and petroleum products are used to synthesize rubber.
Just as natural rubber is made from latex, artificial rubber is made from synthetic latex. It is produced from two main substances: butadiene-1,3 and sterol. Butadiene-1,3 is a gas derived from petroleum, and sterol is a liquid produced from petroleum and coal. Butadiene-1,3 and sterol are pumped into large containers containing a soap solution, which facilitates the process of forming rubber particles. Catalysts are added. When the mixture in the container is mixed, it gradually turns into a milky liquid — a synthetic latex that looks very similar to the natural one. When synthetic latex acquires the desired condition, inhibitors are added to stop the reaction. Then the latex is pumped to another container with acid and brine, where it coagulates. Curled pieces of rubber look like gray grains, which are subsequently washed to remove unwanted chemicals. Synthetic rubber is dried and compressed into pellets.
There are different types of synthetic rubber. They are produced by adding various additional substances or combining them in a special way.