Vulcanized discovery

Vulcanization was first reported in 1839 with the discovery that heating natural mbber with sulfur and basic lead carbonate produced an improvement in physical properties (2). In 1906, aniline was the first organic compound found to have the abiUty to accelerate the reaction of sulfur with natural mbber (3). Various derivatives of aniline were soon developed which were less toxic and possessed increased acceleration activity. 

In 1839, Charles Goodyear discovered that sulfur could cross-link polymer chains and patented the process in 1844 [1]. Since then rubber became a widely usable material. By the year 1853, natural rubber (NR) was in short supply. So attempts were made to undo what Goodyear had accomplished. Goodyear himself was involved in trying to reclaim vulcanized rubber to overcome the shortage of NR. Later, as a consequence of World War I, Germany introduced synthetic rubbers, namely the Buna rubbers, which raised the curiosity of polymer chemists all over the world. Subsequently, synthetic rubbers with tailor-made properties were born. This was followed by the discovery of new methods and chemicals for vulcanization and processing. It is obvious... 

Lord Kelvin s close associate, the expert experimentalist J. P. Joule, set about to test the former s theoretical relationship and in 1859 published an extensive paper on the thermoelastic properties of various solids—metals, woods of different kinds, and, most prominent of all, natural rubber. In the half century between Gough and Joule not only was a suitable theoretical formula made available through establishment of the second law of thermodynamics, but as a result of the discovery of vulcanization (Goodyear, 1839) Joule had at his disposal a more perfectly elastic substance, vulcanized rubber, and most of his experiments were carried out on samples which had been vulcanized. He confirmed Gough s first two observations but contested the third. On stretching vulcanized rubber to twice its initial length. Joule ob-... 

The vulcanization of rubber is often called one of the great accidental discoveries. But really, it was because Charles persisted in his work despite setbacks, and because his mind was prepared to see the importance of the discovery.There are now over 21 million metric tons of natural and synthetic (manufactured) rubber produced each year. Over half of all manufactured rubber is used for tires the rest is used for hoses, gloves, and other products.The GoodyearTire Rubber Company was named after Charles Goodyear, although he died 30 years before it was founded. 

Prior to the discovery of the vulcanization or cross-linking of hevea rubber with sulfur by Goodyear in 1838, Faraday has shown that the empirical formula of this elastomer is CsHg making it a member of the terpene family. The product obtained by pyrolysis of rubber was named isoprene by Williams in 1860 and converted to a solid (polymerized) by Bouchardat in 1879. 

Although sulfur vulcanization has been studied since its discovery in 1839 by Goodyear, its mechanism is not well understood. Free-radical mechanisms were originally assumed but most evidence points to an ionic reaction [Bateman, 1963]. Neither radical initiators nor inhibitors affect sulfur vulcanization and radicals have not been detected by ESR spectroscopy. On the other hand, sulfur vulcanization is accelerated by organic acids and bases as well as by solvents of high dielectric constant. The ionic process can be depicted as a chain reaction involving the initial formation of a sulfonium ion (XI) by reaction of the polymer with polarized sulfur or a sulfur ion pair. The sulfonium ion reacts with a polymer molecule by hydride... 

Around 1850, S. Wetherill of the New Jersey Zinc Company perfected a roasting furnace in which a grate was charged with coal and then covered with a mixture of zinc ore and coal. The zinc was reduced by the partial combustion of the coal and reoxidized at the furnace exit (direct or American process). These furnaces were subsequently improved but are now no longer used. During the second half of the 19th century, the use of ZnO in rubber was introduced to reduce the time needed for vulcanization. The discovery of the first organic accelerators for vulcanization in 1906 added to the importance of ZnO, which acts as an activator in these materials. 

As with any scientific endeavor, chance discovery played an important role in the development of polymers. In all cases, however, there was a scientist with an open and innovative mind who was ready to recognize and take advantage of a chance observation. Charles Goodyear accidentally tipped sulfur into heated natural rubber to discover vulcanized rubber. Christian Schobein inadvertently wiped up a nitric acid spill with a cotton rag to discover nitrocellulose. Jaques Brandenberger thought of cellophane as he observed the accidental stains on tablecloths. Also, as was discussed in Chapter 1, Teflon was discovered upon the unexpected disappearance of a chemical in a gas cylinder that Roy Plunkett was compelled to saw in half. 

The importance of crosslinked polymers, since the discovery of cured phenolic formaldehyde resins and vulcanized rubber, has significantly grown. Simultaneously, the understanding of the mechanism of network formation, the chemical structure of crosslinked systems and the motional properties at the molecular level, which are responsible for the macroscopic physical and mechanical properties, did not accompany the rapid growth of their commercial production. The insolubility of polymer networks made impossible the structural analysis by NMR techniques, although some studies had been made on the swollen crosslinked polymers. 

A critical requirement for obtaining engineering properties from a rubbery material is its existence in a network structure. Charles Goodyear s discovery of vulcanization changed natural rubber from a material that became sticky when hot and brittle when cold into a material that could be used over a wide range of conditions. Basically, he had found a way to chemically connect the individual polymer chains into a three-dimensional network. Chains that previously could flow past one another under stress now had only limited extensibility, which allowed for the support of considerable stress and retraction upon release of the stress. The terms vulcanization, rubber cure, and cross-linking all refer to the same general phenomenon. 

The discovery of the first organic accelerators for vulcanization in 1906 added to the importance of ZnO, which acts as an activator in these materials. 

Sulfur has relatively few uses as an element. One of the most important of those uses is in vulcanization. Vulcanization is the process of adding sulfur to rubber to make it stiff and hard. It keeps the mbber from melting as it gets warmer. The discovery of vulcanization by Charles Goodyear (1800-1860) in 1839 is one of the greatest industrial accomplishments of modern times. 

Goodyear, Charles (1800-1860). Discovered vulcanization of rubber (1844) by sulfur, inorganic accelerator, and heat. Hancock in England made a parallel discovery. 

Public awareness of natural rubber began as a scientific curiosity, when it was discovered by Priestley that it could be used to rub out pencil marks. This novel capability gave the material its name, but still gave rubber little utility because of its dimensional instability and poor durability. The discovery of vulcanization by Charles Goodyear in 1839 changed all this. Vulcanization, or the heating of natural rubber mixed with small amounts of sulfur. 

---