BS 903 and vulcanized Rubber – a brief bounce back through history

What is Vulcanized Rubber?

Vulcanized rubber is a mixture of rubber and a curing ingredient, usually sulfur, which is then heated under pressure. The rubber becomes more elastic, durable, and more resistant to extremes in temperature.  The process is named after Vulcan, Roman God of Fire.

Vulcanized material is less sticky than raw rubber and has superior mechanical properties.  It is used in the production of shoe soles, hoses, rubber seals and gaskets.  Hard vulcanized rubber is sometimes sold under the brand names ebonite or vulcanite, and is used to make hard articles such as bowling balls!

Goodyear and Hancock

The process was invented by the US inventor Charles Goodyear in the 1830’s - the namesake of the Goodyear Tire and Rubber Company.  Back then, gum elastic was being used and experimented with for many products, but manufacturers had not yet found a way of making the rubber stable over time. It was susceptible to rotting, and aged quickly.  Goodyear decided to try to find a way to make rubber stable so that it would last a long time under adverse conditions.

Through experiments Goodyear tried mixing Indian rubber with various compounds, but no mixtures produced the effect he wanted until 1839.  According to tradition, he accidentally spilled a mixture of India rubber and sulfur onto a hot stove, but in later writings, he denied that the discovery was accidental.  There is some speculation therefore that he may have tried heating the mixture as part of his experiments.

In 1844 the process was sufficiently perfected that he felt it safe to take out a patent in the US.

In 1852 Goodyear travelled to Europe and saw the British inventor Thomas Hancock.  Hancock claimed to have invented vulcanization independently, and received a British patent, initiated in 1843, but finalized in 1844.  In 1855, Hancock's patent was challenged in court with the claim that he had copied Goodyear after noticing sulfur residue on rubber samples that Goodyear has distributed to Europe.  Hancock won the case and his patent in the UK remained.

British Standards appear

During the 1930’s, several British Standards for rubber products appeared, covering rubber joint rings for gas mains, rubber conveyors and elevator belting, jointing rings for pipes, and hoses.  During the preparation of these standards it became apparent co-coordinating test methods would be helped by the issue of a British Standard on rubber testing. The Research Association of British Rubber Manufacturers proposed to BSI that a publication combining all rubber testing methods would be of general value to the industry.

In 1940, two rubber testing standards were issued – BS 902 (methods of Testing Latex, Raw Rubber and Unvulcanized Compounded Rubber) and BS 903 (methods of testing Vulcanized Rubber).

A greatly expanded version of BS 903 appeared in 1950.

Throughout the 1950’s and 60’s, many parts to BS 903 were released as separate publications.  BS 903 Part A1 (Determination of Density and Specific Gravity) was the first, and was followed by at least 30 more in the Part A, B and C series.  BS 903:1950 as a separate publication was withdrawn in 1966.

In 1990 the title of BS 903 was changed to “Physical testing of rubber" as many of the methods in the BS 903-A series are suitable for testing thermoplastic as well as vulcanized rubber. The change of title also anticipated the transfer of the methods in the Part B series to a separate standard for the chemical testing of rubber.

What’s available in the Knowledge Centre?

BSI’s Knowledge Centre can provide access to withdrawn BS 903 series back to its first appearance in 1940. Members can view withdrawn standards without charge in Chiswick, and they are available for purchase in hard copy and PDF. BSI members receive a 50% discount, free postage and can buy on account.

To find out more please contact the Knowledge Centre at: knowledgecentre@bsigroup.com or on +44 (0)20 8996 7004

 


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