Plastics come of age. Great periods in history are marked by the materials and activities for which they are remembered. The Ages of Stone, Bronze and Iron, each apparently grander than its predecessor, have passed. It was iron that made possible the great machines on which the Industrial Revolution swept into the twentieth century. For a time, engineers were content to use cast iron and mild steel as their principal structural materials. Then copper emerged as a major material in the electric power industry. Copper alloys, especially brass, were the next to be widely used, along with lead for plumbing and roofing and zinc for protecting steel – a new material that was to reach hitherto unknown heights in strength and durability.
Mighty steel, however, after only a short reign, is now in danger of being toppled from its powerful position in the materials league. Its major rival is a range of new plastics that, until recently, would have been seen as fit only for cheap goods.
Today, plastics rate fourth in the world league of volume of materials used. Steel is third, cement second and, surprisingly, wood – humanity’s oldest – is the first. Throughout the history of civilization, materials have been selected on the basis of convenience and availability, and these criteria have predominantly determined price. Perhaps no other material is more convenient than wood – it is easily worked and is readily available. Moreover, it is one of our few renewable materials.
Similarly, cement is convenient. Its raw materials are easily quarried and local supplies are plentiful. Steel is altogether different. Although it is used most extensively in the developed countries, the iron ore from which steel is made comes largely from politically sensitive areas in the developing world, from which there is no guarantee of future supplies. Furthermore the alloying elements that give steel its unique properties, mainly chromium, nickel, molybdenum and manganese, are susceptible to wide variations in price and are sometimes prohibitively expensive.
In addition to the cost of the raw materials, processing steel is extremely expensive – both in monetary terms and, perhaps more significantly, in terms of energy.
Already, plastics are used extensively in packaging, furniture, electric products and the transportation industry. The cars of tomorrow will contain many more plastic components than at present.