1 - Introduction to Plastic

Chapter Overview :

1.1 Definitions of  plastics and polymers
1.2 History of plastics
1.3 Raw material supply and pricing
1.4 Strategic material
1.5 The plastics industry
1.6 Uses of plastics in modern

1.1 Definitions of Plastics and Polymers

If only materials are only structural solids at normal temperatures are examined, three major
types of materials are encountered: metals, polymers, ceramics. The polymer materials
can be further divided into synthetic polymers and natural polymers.

Illustrate the definition of plastics.

Definition of Polymers 

Polymers can be gained by imaging them to be like a chain or, perhaps, a string of pearls

, where the individual pearls represent small molecules that chemically bonded together. Therefore, a polymer is molecule made up of smaller molecules that are joined together by 

chemically bonded. Molecule : Bond = Pearl : String.  

1.2 History of Plastics 

The history of humankind's use of polymers and eventually development of plastics has followed

a general pattern of events : 

1. Discovery of the polymers. (This usually implies a naturally occurring polymer, but some 

    discoveries of synthetic polymers were made in the laboratory unintentionally.)

2. Use of  polymer (The early applications were usually based upon the obvious properties of

    the polymer and required little modification of the material.)

3. Realization of deficiencies of material and attempts at modification usually by trial and error.

4. Investigation of the properties of the material and development of a conceptual view or model

    of the material's basic nature. (This step may take many years.)

5. Systematic modification or synthesis of materials that might mimic the properties of the

    natural polymer or, in latter cases, development of synthetic materials that do not have natural

    analogues but have useful properties in their own right.

Since the beginning of the history, people have benefited from natural occurring polymers.

These polymers have provided the raw materials for satisfying basic needs such as clothing

(cotton, wool, silk, flax, fur), shelter (lumber, asphalt), and food (starch, protein) and many higher

needs such as communication (papyrus, wood pulp), music (strings, glues, reeds, lacquers)

, decoration (amber), defense and war (arrows spears, bows), and recreation (rubber). Most

of these polymers could be used with only minor modifications, such as weaving the wool or the

cutting and shaping of wood.

In 1839, Charles Goodyear discovered that natural rubber heated with sulfur retained its

elasticity over a wider range of temperatures than the raw rubber and that it had greater

resistance to solvents. This process to be called Vulcanization.   

The combination of good structural models and several polymerization methods (addition and

condensation), coupled with the needs of War World II and the post war consumer boom,

resulted in rapid developments of many new polymers and hundreds of diverse new applications

for plastics. Teflon was discovered by accident and then synthesized and became an important

material for wire insulation, chemical-resistant, and non-stick applications. 

The combination of plastics with fiber reinforcement materials, usually ceramics or metals, but

occasionally very strong and stiff polymers, provided further advances in properties available to

society called Composite.  

The history of plastics began with people's use of  and curiosity about natural polymers.

Improvement of these natural polymers was inevitable. Over time fortuitous events led to the

discovery and characterization of synthetic polymers. 

1.3 Raw Material Supply and Pricing 

  

Modern plastics are generally made from small molecules and built up into polymeric chains

rather than by converting existing natural polymers into plastics.  The small molecules used to

make most plastics have been derived chiefly from crude oil. 

1.4 Strategic Materials  

Germany, for instance, was cut off from the world's supply natural rubber during World War II.

Because rubber was critical to the German goals, a substitute had to be found. The result was

synthetic rubber (a plastic), which served most of the applications previously served by natural

rubber. In the United States the silk supply was cut off. This was an impetus for the creation of

nylon. Nylon was designed as a silk substitute but became widespread as a rope materail

during World War II, even though its substitution for hemp, the previously dominant rope material,

was not a major target for the original nylon development.

1.5 The Plastics Industry

Dupont, ExxonMobile, Dow, Bayer, BASF, and Huntsman.

1.6 Uses of Plastics in Modern Society

Slip over...

I knew the history of plastics is monotonous, have you found something hang on the seat ??

Let's talk about the Nylon. Pan AM TV Series.

The Development of Nylon

In 1928, the DuPont Company hired a brilliant 32-year-old research chemist,

Wallance Carothers, who had graduated with a Ph.D. from the University of Illinois and then

taught organic chemistry at Illinois and Harvard universities. DuPont agreed that Carothers

would be given the finest staff and facilities in order to develop a concept that he had been

exploring. He believed that he might be able to create a giant molecule ( a large polymer ) by a 

new technique that involved a series of condensation reactions. 

In condensation reactions molecules combine to create larger molecules and a by-product 

molecule, like water, that condenses out of the reaction like dew condensing out of the 

atmosphere on a humid evening. 

Carother's idea was to choose reactants molecules that had two reactive ends  so that each

molecule could be chemically connected (bonded) to two others. If reacted in series and if 

continued long enough, the result would be a very long chain made up of the starting molecules

all bonded together (a polymer).

DuPont management that such a material made up of bonded molecules would be similar to

naturally occurring polymers such as silk. The research objectives for Carothers were, therefore,

to explore the concepts of this new reaction (pure research) but to keep in mind that the end 

result would be a usable product, ideally a synthetic silk (applied research).

The soundness of Carother's concept was demonstrated in 1930 when his chief associate, 

Dr. Julian Hill, observed that the compound he had been treating in the molecular 

( a device that removed the by-product and thereby encouraged the condensation reaction to 

continue, ) had become tough and semirigid, yet elastic. These were properties long associated

with natural polymers.  The change of the reactants into these polymeric materials was clear

evidence that Carothers' team was on the right track. Carothers named the new materials 

" Superpolymers."

About two weeks later, Hill made a second highly important observation. While investigating

the properties of the solid material, Hill found that when melted, the thick, molasses-like material

could be pulled into a fiber shape that was not brittle but was tough and surprisingly strong.

Some of the basic research objectives had been met -- a reaction to make a polymer, the

equipment to extend the chain, and as strong, pliable fiber -- but the material still melted at too 

low a temperature,softened in hot water, and was sensitive to normal cleaning fluids. Obviously

it was not yet viable substitutes for silk. The research team had been working on a reaction

system that made a class of organic chemicals known as Esters. Although these would later 

become a large and important group of polymers, further research was needed. For a time, 

both projects bogged down trying to improve physical properties.

Carothers became diverted and turned his attention to reactions of molecules containing the

organic chemical group acetylene. He felt that this system could lead a synthetic rubber. This

work paralleled the work of other chemists and, although many chemicals were developed, the synthetic rubber he sought was not formulated. ( One of the discoveries he made was an oil that

had an odor of musk, a highly prized ingredient in perfume that was, up to then, obtained only

from the rare musk-ox of Asia at almost prohibitive price.)

At the urging of his associates, Carothers returned to the concept of a synthetic silk. He

conceived a more practical synthesis route and focus on a different class of organic chemicals,

the amides, as the linking connection in the polymers. On May 23, 1934, another 

" Superpolymer " was synthesized by this new technique. This time, Carothers himself 

demonstrated how the " superpolymer " could be made into a fiber. He drew the hot viscous

substance into a syringe and from the needle squirted a tiny stream of it into the air. The floating

stream cooled into wispy filament, as fine as those of a spider's web. The lustrous filament had

excellent heat stability, withstood normal washing and cleaning, and was equal in strength and 

pliability to silk and other natural fibers such as cotton and wool. 

Here, said Carothers, walking into the office of the DuPont chemical director in charge, is your

synthetic textile fiber.

The DuPont Company began an intensive effort to build an experimental or pilot plant to

produce sufficient quantities of the material so that the commercial could be run. The material 

labeled by Carothers as 6/6 polyymer was selected as the most promising for immediate

investigation from the strictly practical standpoint. Eventually, the pilot plant produced the 

materials and small-scale manufacturing was demonstrated. 

On October 27, 1938, almost 11 years after the hiring of Carothers, DuPont publicly announced the development of " a group of new synthetic polymers " from which, among numerous 

applications, textile fibers could be spun of a strength-elasticity factor surpassing that of cotton,

linen, wool, rayon, or silk.

The new group of synthetic materials based on amide reactions was given the name nylon and

quickly captured the imagination of the world. Newspaper hailed the discovery as " one of most

important in the century of chemistry. " The first product made from nylon was bristles for 

toothbrushes. DuPont exhibited nylon stockings as the 1939 World's Fairs of New York and 

San Francisco. Nylon hosiery ( quickly dubbed " nylon " ) created a sensation when, 

on May 5, 1940, the first limited quantities were placed on sale. This began the " Nylon Riots ",

  and during the nest 12 months approximately 64,000,000 pairs of all-nylon hose were bought

by American women, whose demand far exceeded the supply.

Few, if any, major inventions have been so immediately successful as nylon. By the end of 1941,

DuPont had yarn plants in operation or being built capable of producing more than 2 million

miles of nylon yarn daily. By 1941, most  of toothbrushes made in United States, half of the

hairbrushes, and scores of industrial and household brushes were being bristled with nylon

filaments. Nylon was being used for tennis and badminton racquet strings, catheters, 

surgical sutures, fishing lines, musical stings,wire insulation, holt-melt glues, 

self-lubricating bearings, and many wartime applications such as parachutes and ropes.

Carothers sudden death in 1937 cut short a career that might have added other contributors.

It would be difficult, however, to surpass the contribution he made to plastics technology with

the development of nylon

Summary

Plastics are very large molecules that are synthetic and can be or have been shaped. This 

definition generally excludes unmodified or slightly modified natural polymers. If the natual

polymer has been substantially modified, the material can be considered a plastic, assuming

it is formable. ( Obviously some arbitrariness or opinion is contained in the assignment of some

materials, but that represents the situation in practice where some people and organizations 

consider some borderline materials to be plastics and others do not. On most materials,

however, widespread agreement exist.)

The history of plastics illustrates the principles of scientific investigation and development for

materials.