The amazing properties of rubber and the amazing story of its invention

December 29, 2014 , Vassili Philippov

What do you feel when the goal of your life, which you devoted the last 15 years to, has been achieved? What’s next? The life story of Charles Goodyear, the inventor of rubber, who was born on this day, is just as unusual as the physical properties of rubber itself. Why do most bodies expand when heated and tires, on the contrary, shrink

Since time immemorial, Indians used goods made from the sap of the rubber tree: played with natural rubber balls, covered boat bottoms, made shoes out of it. Europeans, along with smoking, potatoes and chocolate, took over rubber from the Indians as well. Erasers were made of this material. Later, a Scottish chemist named Charles Macintosh while conducting a regular experiment smeared his sleeve jacket with a solution of rubber in turpentine and after a while noticed that the sleeve does not get wet. He patented and began producing waterproof coats - macintoshes.

Natural rubber is one of the simplest natural polymers. It consists of long chain-molecules which consist of repeating blocks:

isoprene

There may be tens of thousands of such blocks in one molecule.

polyisoprene

Such a structure has its drawbacks - natural rubber poorly keeps shape. Separate unbounded chain-molecules easily slip over each other, and the material ‘flows’. Because of this natural rubber becomes tacky and soft in warm weather.

The amazing story of the invention

In the first half of the 19th century many people’s minds were busy trying to get rid of this unpleasant property of natural rubber, while keeping all its advantages. As they used to say: to “cure” natural rubber. The American inventor Charles Goodyear also tackled this problem.

Charles Goodyear

And tackled it with passion. Working at home in the kitchen, by trial and error he mixed natural rubber with all that was at hand: coal, sugar, salt, pepper, oil, ink, in the hope that some substance binds natural rubber. His path was thorny. On the way were false hopes, disappointments, partner bankruptcy, and family hunger. But in the end, Charles found a way to “cure” natural rubber. One day he accidentally dropped natural rubber mixed with sulfur into the fireplace. The burnt piece became exactly the way Charles Goodyear wanted to see it.

Despite all of this Goodyear knew little about chemistry. Even having found a way to produce rubber, he did not understand its principles. The second part of his life Charles spent trying to convince the world of the usefulness of his invention. Unfortunately, his sad story does not become happy from now on. Even finding a way to do what he wanted most of his life, Charles was unable to make money on it. He spent all his money on exhibitions, patent disputes, and died in debt.

The amazing properties of rubber

In addition to the human drama, this story is also interesting about what is happening within rubber on a molecular level. Remember, we discussed that the long chain-molecules in rubber easily slip over each other, and this is the cause of its unpleasant properties? So what if these chain-molecules are glued together in some places? This is the process discovered by Goodyear. Sulfur atoms form a “bridge” between the long molecules of rubber, gluing them together and not allowing them to slip.

And how are the remarkable properties of rubber to expand and shrink back explained? What makes it such a wonderful material for slingshots? To understand this we must look at the structure of the molecules of rubber. Here I’ll give the word to Richard Feynman, it is hardly possible to explain it more evidently and clearly – he is definitely a genius!