What
Are Plastics?
By
Paul Gottlich
www.mindfully.org
History
In this era of many astonishing industrial developments, probably no industry
has under gone such rapid growth and development as the plastics industry.
According to most authorities in this field, the plastics industry really began
in 1868.
A young American printer, named John Wesley Hyatt, was
searching for a new material to be used as a substitute for ivory in the making
of billiard balls. A $10,000 prize had been offered for such a discovery. He
found that cellulose nitrate, formed by the action of nitric acid on cotton
cellulose, mixed with camphor and treated with proper amounts of pressure and
heat, produced a substance which could be molded into desired shapes. He called
his new material "Celluloid."
It was not until almost the beginning of the twentieth century that a
second plastic was produced. Adolph Spitteler, a German,
mixed sour milk and formaldehyde together to form a material which was
really a casein plastic. In 1909, Dr. Leo Baekeland, an
American born in Belgium, was trying to produce a synthetic resin. He did
this successfully by mixing phenol and formaldehyde together under certain
conditions, thus producing the first synthetic resin. This new plastic was
called "Bakelite."
Many new plastics have been made since "Bakelite." Production of
plastics has increased over 2000% since "Bakelite" was first produced,
and there are now more than twenty known types.
Research along the lines of plastics has given a great impetus to research
and invention in many other different fields of endeavor. Millions of dollars
are spent yearly in plastics research, trying to find new plastics and to
improve the existing ones.
Much research will be done in the future to lower the cost of producing plastics
so that their consumption will become greater. In spite of the
varied and widespread application of plastics in practically every
phase of everyday life, the possibilities of this wonderful new
material have been by no means exhausted. It seems safe to say
that if the application and use of plastics continue to increase
at the present rate, we may be living in a "Plastics Age."
Terminology
A dictionary of technical terms defines the word "plastic" as
"capable of being molded or modeled". It defines "plastics"
as " nonmetallic moldable compounds and the articles made from them".
Recent use has also given the adjective, "plastic," the additional
meaning of " made of plastics". An apt definition of plastics has been
given by the head of the Monsanto Plastics Research who says, "Plastics
are materials that, while being processed, can be pushed into almost any desired
shape and then retain that shape."
The term "plastics" is a commercial rather than a scientific
phraseology, because rubber and glass are easily formed into any desired shape
during processing, and retain that shape after cooling. The word "plastics"
now generally applies to the synthetic products of chemistry. These chemical
products can be cast, molded, or pressed into an unlimited variety of shapes.
Classification
Plastics, depending on their physical properties, may be classified as
thermoplastic or thermosetting materials. Thermoplastic materials can be formed
into desired shapes under heat and pressure and become solids on cooling. If
they are subjected to the same conditions of heat and pressure, they can be
remolded. Thermosetting materials acquire infallibility under heat and pressure
and cannot be remolded.
Plastics may be classified also according to their chemical sources. The
twenty or more known basic types fall into four general groups:
1. cellulose plastics
include the cellulose nitrates and cellulose acetates. The cellulose
nitrate plastics are the oldest in this group, and "Celluloid"
is the oldest example. These plastics are made from cotton or
wood pulp.
2. synthetic resin plastics
include the phenol formaldehyde, phenolic furfural, urea formaldehyde,
vinyl, styrene, and acrylic plastics. These plastics are made
from phenol, formaldehyde, urea, acetylene, petroleum, glycerol,
and phthalic anhydride.
3. protein plastics
casein plastics are the most common type in the protein group.
They are made from milk. Other protein plastics are made from
soy beans, coffee beans, peanuts, and other agricultural products.
4. natural resins
include shellac, asphalt, rosin, amber,
and pitch. These materials with fillers are usually cold molded.
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