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Today
more than 1000 different plants are known
in the tropics which produce sap, that can be used
for making rubber. The most important one is the
Para rubbertree, from the Amazon valley, that reaches
a height of up to 30 m. The tree needs a year round
temperature of 27º C and a yearly rainfall of 2000
mm. During the dry season it looses its leaves and
the flowers open together with the new leaves. The
fruits open with a loud crack.
To
keep the rubber monopoly to Brasil the
export of the seeds was strictly forbidden during
the last century. In 1877, 70000 seeds were smuggled
to Britain and grown in Kew Botanical Garden/London.
Since 1878 the trees were grown in the British colony
Malaya and in 1901 the Gouvernor of Trang Province
introduced them to Thailand. The first Para rubbertree
ever grown in Thailand is still standing in front
of his house in Kantang.
At
the age of 6-7 years the tree is big enough
and the bark is cut. This is done by the light of
a carbide lamp before sunrise. The milky white sap
runs into coconut halfes and is collected during
the forenoon. In flat tubs it is mixed with fornic
acid and after becoming solid it is rolled between
two cylinders giving it the shape of a small mat.
Most
often the mats hang on bamboo poles in
front of the houses to dry. During this process
the colour changes from white to light or dark brown.
The dried mats are bought by middlemen to deliver
them to factorys, where tires and gloves for single
use are produced. For that purpose sulphur is added
to obtain soft (4-5% sulphur ) or hard rubber (25-30%
sulphur). This vulcanisation process was invented
by Charles Goodyear in 1839 already.
With
1.5 Million tons Thailand is the world's
biggest producer of rubber and together with Indonesia
and Malaysia 75% of the worlds demand are produced.
Main markets are the USA, Germany, Italy, Great
Britain, Japan and South Korea.
After
25-30 years the trees are exhausted and
cut. They are used for burning charcoal and furniture.
On the cleared area new trees are planted.
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