Polystyrene

The invention: A clear, moldable polymer with many industrial

uses whose overuse has also threatened the environment.

The people behind the invention:

Edward Simon, an American chemist

Charles Gerhardt (1816-1856), a French chemist

Marcellin Pierre Berthelot (1827-1907), a French chemist

Polystyrene Is Characterized

In the late eighteenth century, a scientist by the name of Casper

Neuman described the isolation of a chemical called “storax” from a

balsam tree that grew in Asia Minor. This isolation led to the first report

on the physical properties of the substance later known as “styrene.”

The work of Neuman was confirmed and expanded upon

years later, first in 1839 by Edward Simon, who evaluated the temperature

dependence of styrene, and later by Charles Gerhardt,

who proposed its molecular formula. The work of these two men

sparked an interest in styrene and its derivatives.

Polystyrene belongs to a special class of molecules known as

polymers.Apolymer (the name means “many parts”) is a giant molecule

formed by combining small molecular units, called “monomers.”

This combination results in a macromolecule whose physical

properties—especially its strength and flexibility—are significantly

different fromthose of its monomer components. Such polymers are

often simply called “plastics.”

Polystyrene has become an important material in modern society

because it exhibits a variety of physical characteristics that can be

manipulated for the production of consumer products. Polystyrene

is a “thermoplastic,” which means that it can be softened by heat

and then reformed, after which it can be cooled to form a durable

and resilient product.

At 94 degrees Celsius, polystyrene softens; at room temperature,

however, it rings like a metal when struck. Because of the glasslike

nature and high refractive index of polystyrene, products made from it are known for their shine and attractive texture. In addition,

the material is characterized by a high level of water resistance and

by electrical insulating qualities. It is also flammable, can by dissolved

or softened by many solvents, and is sensitive to light. These

qualities make polystyrene a valuable material in the manufacture

of consumer products.

Plastics on the Market

In 1866, Marcellin Pierre Berthelot prepared styrene from ethylene

and benzene mixtures in a heated reaction flask. This was the

first synthetic preparation of polystyrene. In 1925, the Naugatuck

Chemical Company began to operate the first commercial styrene/

polystyrene manufacturing plant. In the 1930’s, the Dow Chemical

Company became involved in the manufacturing and marketing of

styrene/polystyrene products. Dow’s Styron 666 was first marketed

as a general-purpose polystyrene in 1938. This material was

the first plastic product to demonstrate polystyrene’s excellent mechanical

properties and ease of fabrication.

The advent ofWorldWar II increased the need for plastics. When

the Allies’ supply of natural rubber was interrupted, chemists sought

to develop synthetic substitutes. The use of additives with polymer

species was found to alter some of the physical properties of those

species. Adding substances called “elastomers” during the polymerization

process was shown to give a rubberlike quality to a normally

brittle species. An example of this is Dow’s Styron 475, which

was marketed in 1948 as the first “impact” polystyrene. It is called

an impact polystyrene because it also contains butadiene, which increases

the product’s resistance to breakage. The continued characterization

of polystyrene products has led to the development of a

worldwide industry that fills a wide range of consumer needs.

Following World War II, the plastics industry revolutionized

many aspects of modern society. Polystyrene is only one of the

many plastics involved in this process, but it has found its way into

a multitude of consumer products. Disposable kitchen utensils,

trays and packages, cups, videocassettes, insulating foams, egg cartons,

food wrappings, paints, and appliance parts are only a few of

the typical applications of polystyrenes. In fact, the production of polystyrene has grown to exceed 5 billion pounds per year.

The tremendous growth of this industry in the postwar era has

been fueled by a variety of factors. Having studied the physical

and chemical properties of polystyrene, chemists and engineers

were able to envision particular uses and to tailor the manufacture

of the product to fit those uses precisely. Because of its low cost of

production, superior performance, and light weight, polystyrene

has become the material of choice for the packaging industry. The

automobile industry also enjoys its benefits. Polystyrene’s lower

density compared to those of glass and steel makes it appropriate

for use in automobiles, since its light weight means that using

it can reduce the weight of automobiles, thereby increasing gas

efficiency.

Impact

There is no doubt that the marketing of polystyrene has greatly

affected almost every aspect of modern society. Fromcomputer keyboards

to food packaging, the use of polystyrene has had a powerful

impact on both the quality and the prices of products. Its use is not,

however, without drawbacks; it has also presented humankind

with a dilemma. The wholesale use of polystyrene has created an

environmental problem that represents a danger to wildlife, adds to

roadside pollution, and greatly contributes to the volume of solid

waste in landfills.

Polystyrene has become a household commodity because it lasts.

The reciprocal effect of this fact is that it may last forever. Unlike natural

products, which decompose upon burial, polystyrene is very

difficult to convert into degradable forms. The newest challenge facing

engineers and chemists is to provide for the safe and efficient

disposal of plastic products. Thermoplastics such as polystyrene

can be melted down and remolded into new products, which makes

recycling and reuse of polystyrene a viable option, but this option

requires the cooperation of the same consumers who have benefited

from the production of polystyrene products.