2 Goodyear's contribution

Most textbooks have it that Charles Goodyear ( 1800– 1860) was first to use sulfur to vulcanize rubber. Depending on whom you read, the Goodyear story is either one of pure luck, or one of careful research. Goodyear insists that it was the latter, though there are many contemporaneous accounts which indicate the former.

Goodyear claimed he discovered sulfur-based vulcanization in 1839, but did not patent the invention until July 5, 1843, and did not write the story of the discovery until 1853 in his autobiographical book, Gum-Elastica. Meanwhile, Thomas Hancock (1786-1865), a scientist and engineer, patented the process in the UK on November 21, 1843, eight weeks before Goodyear applied for his own UK patent.

The Goodyear Tire and Rubber Company adopted the Goodyear name because of its activities in the rubber industry, but it has no other links to Charles Goodyear and his family.

Here is Goodyear's account of the invention, taken from Gum-Elastica. Although the book is an autobiography, Goodyear chose to write it in the third person, so that 'the inventor' and 'he' referred to in the text are in fact, the author. He describes the scene in a rubber factory where his brother worked.

...The inventor made some experiments to ascertain the effect of heat on the same compound that had decomposed in the mail-bags and other articles. He was surprised to find that the specimen, being carelessly brought into contact with a hot stove, charred like leather.

Goodyear goes on to describe how he attempted to call the attention of his brother and other workers in the plant who were familiar with the behavior of dissolved rubber, but they dismissed his appeal as unworthy of their attention, believing it to be one of the many appeals he made to them on account of some strange experiment. Goodyear claims he tried to tell them that dissolved rubber usually melted when heated excessively, but they still ignored him.

He directly inferred that if the process of charring could be stopped at the right point, it might divest the gum of its native adhesiveness throughout, which would make it better than the native gum. Upon further trial with heat, he was further convinced of the correctness of this inference, by finding that the India rubber could not be melted in boiling sulfur at any heat ever so great, but always charred. He made another trial of heating a similar fabric before an open fire. The same effect, that of charring the gum, followed; but there were further and very satisfactory indications of success in producing the desired result, as upon the edge of the charred portion appeared a line or border, that was not charred, but perfectly cured.

Goodyear then goes on to describe how he moved to Woburn, Massachusetts and carried out a series of systematic experiments to discover the right conditions for curing rubber.

...On ascertaining to a certainty that he had found the object of his search and much more, and that the new substance was proof against cold and the solvent of the native gum, he felt himself amply repaid for the past, and quite indifferent to the trials of the future.

Goodyear never made any money out of his invention. He pawned all his family's possessions in an effort to raise money, but on July 1, 1860, he died with debts of over $200,000.

3 Subsequent developments

Whatever the true history, the discovery of the rubber-sulfur reaction revolutionized the use and applications of rubber, and changed the face of the industrial world.

Up to that time, the only way to seal a small gap on a rotating machine, or ensure that the gas (usually steam) in a cylinder applied its force to the piston with minimal leakage, was by using leather soaked in oil. This was acceptable up to moderate pressures, but above a certain point, machine designers had to compromise between the extra friction generated by packing the leather ever more tightly, or face greater leakage of the precious steam.

Vulcanized rubber offered the ideal solution. With vulcanized rubber, engineers had a material which could be shaped and formed to precise shapes and dimensions, and which would accept moderate to large deformations under load and recover quickly to its original dimensions once the load was removed. These, combined with good durability and lack of stickiness, are the critical requirements for an effective sealing material.

Further experiments in the processing and compounding of rubber were carried out, mostly in the UK by Hancock and his colleagues. These led to a more repeatable and stable process.

In 1905, however, George Oenslager , discovered that a derivative of aniline called thiocarbanilide was able to accelerate the action of sulfur on the rubber, leading to much shorter cure times and reduced energy consumption . This work, though much less well-known, is almost as fundamental to the development of the rubber industry as that of Goodyear in discovering the sulfur cure. Accelerators made the cure process much more reliable and more repeatable. One year after his discovery, Oenslager had found hundreds of potential applications for his additive.

Thus, the science of accelerators and retarders was born. An accelerator speeds up the cure reaction, while a retarder delays it. In the subsequent century, various chemists have developed other accelerators, and so-called ultra-accelerators, that make the reaction very fast, and are used in the compounds used to make most modern rubber goods.

Chemistry

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