Natural Rubber, Industry Sector AGRICULTURE

NATURAL RUBBER

Rubber starts life as a milky emulsion called Latex which is the sap of the Para rubber tree.  It is believed to have been named by Joseph Priestly, an English chemist who, in 1770, discovered that dried latex rubbed out pencil marks.

ORIGINS

In Central and South America, were the tree originates, evidence exists that the sap was being collected as early as 1600BC and the ancient Mesoamerican civilizations had made rubber balls and even dipped their feet in latex to produce a rubber shoe. In Brazil the natives used rubber to make water-resistant cloth.

START OF PLANTATIONS

In 1876 Henry Wickham gathered 70,000 seeds of the rubber tree from Brazil in a scheme financed by the Indian Government. The seeds were sent to Kew Botanical Gardens in England and 2899 plants were raised, this provided the basis for the worlds rubber industry. Rubber trees have been cultivated in plantations for over 100 years in 24 tropical countries in Asia, Africa and Latin America.

The tree which is fast growing to a height of 75ft requires temperatures of 74 - 95F and well distributed rainfall of 75 - 100 inches per year. Trees are planted 15 feet apart and have a useful life of 25 - 30 years.

HARVESTING THE LATEX - TAPPING

Using a jeboug knife a spiral cut is made round half the trunk, a small spout inserted and a cup hung below the spout. Every 1-3 days the cup is emptied and the process starts again with a new cut 1/16 of an inch lower. This continues for 6 months then the tree is rested for 3 months. The herbicide ethephon is used to stimulate the flow.

PROCESSING THE LATEX

The object of processing is to extract the solid rubber from the latex liquid in the same way that butter is made from milk. Originally latex was diluted with water and poured into coagulation tanks,  Acetic or Formic acid was added and after stirring and straining produced 30-35% rubber content. The "curd" was then squeezed between rollers to produce latex sheets. This method has now been largely replaced by massive centrifuges.

MAKING RUBBER STABLE

Uncured natural rubber turns sticky and smelly within a few days and starts to rot. In 1843 Charles Goodyear patented a process called vulcanizing in which the addition of sulphur to the raw rubber stopped it degrading making the material smooth and resistant to melting. More recent technologies have replaced sulphur with organic peroxides.

SYNTHETIC RUBBERS

Shortages of natural materials during World War II accelerated the production of man made rubber which had been mainly experimental since 1906. By 1960 synthetics production had overtaken natural rubber.

MARKET SIZE

The global production of natural rubber in 2003 was 8m tonnes (Source : FAO United Nations)  with the  major producers being Thailand 2.8m Indonesia 1.8m Malaysia 0.9m and India 0.6m tonnes.

Crazy Facts Corner

• If you can't find a rubber tree a fig tree or a dandelion might do, they both produce Latex.

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

Links

http://www.wikipedia.org
http://hort.purdue.edu/newcrop/tropical/lecture_22/lec_22.html
http://www.iisrp.com/synthetic-rubber.html

Researched by DynamicDave