HISTORY OF PLASTICS
The United States plastics industry is a multi-billion dollar business, and it is still growing at a rate faster than most other industries in this country. Plastics have been used in every major market in the United States, including construction, packaging, automobiles and boats, electrical/electronics, pipe and fittings, and consumer goods, to mention just a few.
Plastics are basic materials, on par with metals, glass, wood, and paper, and they are essential to the needs of virtually the entire spectrum of American business. As lifestyles change, plastics will become ever more valuable to tomorrow's advanced new concepts in architecture, aerospace, communications, transportation -- even to medicine and the arts.
Plastic materials trace their origin in this country back to 1868, when a young printer named John Wesley Hyatt came up with Celluloid, the first American plastic. He mixed pyroxylin, made from cotton (one of nature's polymerics), and nitric acid, with camphor to create an entirely different and new product. Celluloid quickly moved into many markets, including the first photographic film used by George Eastman to produce the first motion picture film in 1882. The material is still in use today under its chemical name, cellulose nitrate.
In 1909, Dr. Lee Hendrik Baekeland introduced phenoformaldehyde plastics (or "phenolics", as they are more popularly known), the first plastic to achieve worldwide acceptance. More importantly, Baekeland also evolved techniques for controlling and modifying the phenolformaldehyde reaction so that products could be formed under heat and pressure from the material. This characteristic of liquefying the material so that it can be formed into various shapes under heat and pressure is still common to most plastics.
The third major thrust in the development of plastics took place in the 1920s with the introduction of cellulose acetate (which is similar in structure to cellulose nitrate, but safer to process and use), ureaformaldehyde (which can be processed like the phenolics, but can also be molded into light colored articles that are more attractive than the blacks and browns in which phenolics are available), and polyvinyl chloride (PVC, or vinyl, as it is commonly called). Nylon was also developed in the late 1920s through the classic research of W.T. Carothers.
Each decade saw the introduction of new and more versatile plastics. In the 1930's, there were acrylic resins for signs and glazing and the commercialization of polystyrene, which became the third largest-selling plastic, literally revolutionizing segments of the house wares, toys, and packaging industries. Melamine resins were also introduced; these later became a critical element (in the form of a binder) in the development of decorative laminate tops, vertical surfacing, and the like.
Polyethylene -- today's most widely used plastic -- evolved out of the need for a superior insulating material that could be used for such applications as radar cable during World War II. The thermoset polyester resins that only a decade or so later were to radically change the boat-building business in the United States were also a wartime development introduced for military use. And acrylonitrile-butadiene-styrene plastics, or ABS, (the plastic most often used today in appliance housings, refrigerator linens, safety helmets, pipe, telephone headsets, and luggage) owes its origins to research work emanating from the crash wartime program aimed at producing large quantities of synthetic rubber.
The decade of the 1950s saw the introduction of polypropylene and the development of acetal and polycarbonate, two plastics that, along with nylon, came to form the nucleus of a sub-group in the plastics family known as the "engineering thermoplastics." Their outstanding impact strength and thermal and dimensional stability enabled them to compete directly and favorably with metal in many applications.
The 1960s and 1970s also saw their share of new plastic introductions, most notably thermoplastic polyesters with the kind of outstanding resistance to gas permeation that made them applicable for use in packaging. During this period, another sub-group of the plastics family also started to emerge, the so-called "high temperature plastics," which includes the polyimides, polyamide-imides, aromatic polyesters, polyphenylene sulfide, polyether sulfone, and the like. These materials were designed to meet the demanding thermal needs of aerospace and aircraft applications. Today, however, they have moved into the commercial areas that require their ability to operate at continuous temperatures of 400 degrees F, or more.
Estimates are that by the year 2000, plastics materials will have grown to a 225 billion pound production level in the United States alone, making them one of the world's most important materials of use.
A Starting Point For Plastics
Like any material, plastics have their origins in nature, in such basic chemical elements as carbon, oxygen, hydrogen, nitrogen, chlorine, or sulfur. These materials are extracted from nature's storehouse of air, water, gas, oil, coal, and even plants.
From the basic sources come the feedstock's we call "monomers" (from "mono", which means one, and "mer", which means unit - in this case, the specific chemical unit). The monomer is subjected to a chemical reaction known as polymerization, which causes the small molecules to link together into longer molecules. Chemically, the polymerization turns the monomer into a "polymer" (many mers). Thus, a polymer may be defined as a high-molecular-weight compound which contains comparatively simple recurring units.
A monomer can contribute to the manufacture of a variety of different polymers, each with its own distinctive characteristics. The way in which the monomers link together into polymers, and resulting structural arrangement, is one determinant of the properties of the plastic. The length of the molecules in the molecular chain (referred to as "molecular weight") is a second determinant. And the type of monomer is a third determinant. Polymerizing two or more different monomers together (a process known as "copolymerization") is a fourth determinant. Incorporating various chemicals or additives during or after polymerization is a fifth.