帖子 由 Giraffe 于 周二 七月 28, 2009 7:29 am

What is the rubber

What is Rubber? Rubber is a sticky, elastic solid produced from a milky
liquid called "latex," which has different properties than the sap
found in trees. Although latex is found in the bark, roots, and stems,
branches, leaves, and fruit of over 400 different plants and trees, the
bulk is found, and extracted, from the inner bark of the branches, and
from the trunk, of the rubber tree. Quite simply, it would not be
cost-effective to extract the latex from rubber producing plants, such
as the dandelion, the milkweed, and the sagebrush. Just visualize some
poor soul laboring over one of these with a syringe!

Rubber, derived from the gum of a tree, has existed since prehistoric
times. For example, fossils of rubber-producing plants date back almost
3,000,000 years. Crude rubber balls, discovered in ruins of ancient
Incan and Mayan civilizations in Central and in South America, are, at
very least, 900 years old. Natives of Southeastern Asia used rubber,
prepared from the "juice" of trees to waterproof their baskets and
jars. Even Columbus, on his second voyage to the New World, observed
Haitian natives playing with balls made from "the gum of a tree."

Latex consists of tiny particles of liquid, solid, or semi-fluid
material, that appears in the form of a watery liquor, not to be drunk!
The breakdown on this watery liquid is only about 33% rubber, with the
remainder being, not surprisingly, water! When the rubber particles in
the latex join together, they form a ball of rubber.

Rubber producing plants grow best within 10 degrees of the Equator,
where the climate is hot and moist, and the soil is deep and rich. For
this reason, the area of about 700 miles on each side of the Equator is
known as the "Rubber Belt." Brazil, from whence the best, and
top-producing rubber tree hails, is firmly planted within the Rubber
Belt. This Latino tree with a Latin name, Hevea brasiliensis, produces
approximately 96% of the world's supply of natural rubber, and now is
cultivated in other Rubber Belt countries.

Most likely, the French, prior to the 1800s, were the first white
men to take advantage of rubbers' elasticity. They manufactured "rubber
bands" for use with their garters and their suspenders, to help to keep
their pants up. Rubber belts did not exist at that time.

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