Page 49 - FOUNDATIONS FOR LIFE; EXPLORING GOD’S UNIVERSE

Science Y5 – God’s Amazing Matters – lesson 7
In its native Central America and South America, rubber has been collected for a long time. The
Ancient Mesoamericans had a ball game using rubber balls and a few Pre-Columbian rubber balls
have been found (always in sites that were flooded under fresh water), the earliest dating to about

1600 BC. The Maya also made a type of temporary rubber shoe by dipping their feet into a latex
mixture. Rubber was used in various other contexts, such as strips to hold stone and metal tools to
wooden handles, and padding for the tool handles. In Brazil the natives understood the use of rubber
to make water-resistant cloth.

When samples of rubber first arrived in England, it was observed by Joseph Priestley, in 1770, that

a piece of the material was extremely good for rubbing out pencil marks on paper, hence the name.

The Para rubber tree initially grew in South America, where it was the main source of what limited
amount of latex rubber was consumed during much of the 19th century. About 100 years ago, the
Congo Free State in Africa was a significant source of natural rubber latex, mostly gathered by
forced labour.

Properties

Rubber latex (milky juice of rubber tree)

Rubber exhibits unique physical and chemical properties.

Rubber's stress-strain is often modeled as hyper-elastic.

Rubber strain crystallizes.

Current sources of rubber

Close to 21 million tons of rubber was produced in 2005 of which around 42% was natural. Today
Asia is the main source of natural rubber, accounting for around 94% of output in 2005. The three
largest producing countries (Indonesia, Malaysia and Thailand) together accounts for around 72% of
all natural rubber production.

Early experiments in the development of synthetic rubber led to the invention of Silly Putty.

Natural rubber is often vulcanized, a process by which the rubber is heated and sulphur products are
added to improve resilience and elasticity, and to prevent it from perishing. Vulcanization greatly
improved the durability and utility of rubber from the 1830s on. The successful development of
vulcanisation is most closely associated with Charles Goodyear. Carbon black is often used as an
additive to rubber to improve its strength, especially in vehicle tyres.

Uses

The use of rubber is wide spread, ranging from household to industrial products, entering the
production stream at the intermediate stage or as final products. Tyres and tubes are the largest
consumers of rubber, accounting for around 56% total consumption in 2005. The remaining 44% are
taken up by the general rubber goods (GRG) sector, which are all products except tyres and tubes.

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