Page 315 - Academic Press Encyclopedia of Physical Science and Technology 3rd Polymer

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Encyclopedia of Physical Science and Technology EN014B-670 July 28, 2001 16:50

Rubber, Natural

Stephen T. Semegen
STS Technical Services

I. Introduction
II. Agriculture
III. Preparation
IV. Modified Rubber and Derivatives
V. Properties
VI. Product Usages
VII. Economics
VIII. Research

GLOSSARY Transition, glass Reversible change in a material from a
viscous or rubbery state to a brittle glassy state.
Crystallization, polymer Arrangement of previously Vulcanization Irreversible process changing the chemi-
disordered polymer segments of repeating patterns into cal structure of a rubber (cross-linking), becoming less
geometric symmetry. plastic, more elastic, and extending the usable temper-
Latex, rubber Colloidal aqueous dispersion of rubber. ature range.
Monomer Low-molecular-weight substance consisting
of molecules capable of reacting to form a polymer.
Polymer Three-dimensional substance of molecules NATURAL RUBBER is a cis-1,4-polyisoprene obtained
characterized by repetition of one or more monomer from a botanical source and is the oldest known rubber. It
units. is also the most versatile one for fabrication into rubber
Rubber Materialthatiscapableofrecovering(retracting) products. Before World War II, natural rubber accounted
quickly from large deformations. for practically 100% of all rubber usage. Two-thirds of
Rubber product Item of commerce whose major portion this total usage is for tires. However, natural rubber did
consists of rubber. not become an important industrial commodity until the
Rubber, raw Vulcanizable macromolecular material, discovery of sulfur vulcanization in 1839 and the invention
used to produce a rubber product. of the pneumatic tire in 1888.
Tack, rubber Property causing contacting surfaces of Even so, natural-rubber-containing trees originally
raw rubber to adhere to each other. grew wild in the jungles of South America. They had
Transition, first order Reversible change in phase of a to be domesticated and raised as an agricultural crop
material, as in melting or crystalization of polymers. on cultivated farms and plantations. Finally, a tapping

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