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The History of Plastics
The History of Plastics
Introduction
Since pre-historic times, man has exploited for his own use the properties of natural polymers such as horn, waxes and bitumens. Over the years, it was gradually learned that the properties of such materials could be improved by techniques such as purification and modification with other substances.
By the turn of the 19th century, with the explosion of scientific knowledge in fields such as chemistry and physics, coupled with demands from industry for materials with properties which could not be found in Nature, the scene was set for the development of a whole range of new materials —among them the early plastics.
The Natural Polymers
In the 17th century, an Englishman, John Osborne made mouldings from the natural polymer, horn. By the 19th century, the moulded horn industry was thriving and geared to sell mass produced items to the emerging middle classes.
Gums from tropical trees were exploited, especially rubber and gutta percha for which Bewley invented the plastics extruder in 1847. Gutta percha was used to protect and insulate the first submarine telegraph cables in 1850.
With his brother Charles, Thomas Hancock worked extensively with this material but is now best known for his discovery (1839) of the vulcanisation of rubber whilst Goodyear independently discovered it in America. Theirs was the first deliberate chemical modification of a natural polymer to produce a moulding material.
In America in the 1850’s, shellac was being compounded with wood flour to mould Union cases to display early photographs. Shellac based compositions were used until the 1940’s to mould gramophone records.
Lepage worked in France with albumen and wood flour to produce his decorative Bois Durci plaques, and many others worked with a wide variety of ingredients including seaweed, peat, paper and leather. Nearly 10% of all British patents issued in 1855 referred to moulding materials but the major breakthrough was in the modification of cellulose fibres with nitric acid to give the first semi-synthetic plastics material, cellulose nitrate.
The Semi Synthetics
Cellulose Nitrate (Celluloid, Xylonite, Parkesine)
Cellulose nitrate, known by most people as ‘celluloid’, was the first plastics to achieve real success — but only after many false starts and financial failures. Credit for the invention goes to the British inventor, Alexander Parkes (photo), who displayed his material (which he called Parkesine) at the Great International Exhibition in London, 1862. Among other things, he saw his material as a substitute for the increasingly scarce materials ivory and tortoiseshell and his display of brooches, decorative trinkets and knife handles were to win for Parkes an ‘award for excellence’.
To exploit his invention he formed in 1866 the Parkesine Company but this was soon to go into liquidation as he attempted to cut quality in his drive for lower costs. It was to be a decade or so later, under the direction of the Merriam family and their British Xylonite Company Limited, that the material (by then renamed Xylonite) began to achieve commercial success with products such as combs, collars and cuffs. Most of the credit for commercial success and technical excellence, however, goes to the Hyatt brothers in America with their material, which they called ‘celluloid’. Through the unlikely work to develop a substitute for the ivory, billiard ball they devised a process for manufacturers using a cellulose nitrate composition. In their patent of 1870 they described the all-important discovery —the solvent action of camphor on cellulose nitrate. Among their earliest commercial successes was dental plates for false teeth.
Cellulose Acetate (Bexoid, Clarifoil, Tenite)
Cellulose nitrate had one severe drawback — its flammability This had prevented its use in mass production, rapid moulding techniques. Cellulose acetate, developed around the turn of the century met this problem. Among its early uses were as ‘safety’ film and dope to stiffen and waterproof the fabric wings and fuselage of early aeroplanes. It was initially fabricated like celluloid in the form of rod, sheet or tube but later became available as a moulding powder in various degrees of hardness which could be quickly and economically shaped by injection moulding. As such it did much to encourage the development of injection moulding machinery — one of the key processes in plastics fabrication.
Casein Formaldehyde (Lactoid, Erinoid, Galalith)
Invented at the turn of the century, manufacture was based on fat-free milk to which resin was added to form curds which, when suitably dried, processed and coloured, could be extruded into rods and made into sheets. The material was then hardened in a bath of formaldehyde from whence it was machined into the desired end use. The brilliant colours and patterns made casein a leading material for making products such as buttons, buckles, fountain pen, barrels and knitting needles.
The Thermosetting Plastics
Phenolics (Bakelite, Nestorite, Mouldrite)
Phenolic materials, popularly known as Bakelite, were the first completely synthetic plastics materials. The name ‘Bakelite’ was coined by the Belgian-born inventor Leo H. Baekeland to describe the amber-coloured synthetic resin made by the condensation of phenol and formaldehyde in the presence of a catalyst. In Britain, similar researches were being carried out by a British inventor, Sir James Swinburne whose search for a material with good electrical properties led him to develop similar resinous products. His researches, however, were less complete than those of Baekeland but the two were to get together in the 1920’s to develop the Bakelite business in Britain.
Although widely used as a casting resin which could be poured into moulds to make artefacts such as umbrella handles and pipe stems, or used to impregnate papers and fabrics to make high-pressure laminates of vital interest to the then emerging telephone and radio industries, Bakelite is best known as a moulding material.
Phenol formaldehyde resins have excellent heat resistance and low electrical conductivity Different fillers such as wood flour, mica, asbestos and textile fabric enable considerable strength and resistance properties to be built into the range of products. Applications are innumerable and range from domestic items such as toasters, clocks, fires, radios, ash trays and lavatory seats to car components and electrical fittings.
Amino Plastics
Urea Formaldehyde (Beetle, Scarab, Mouldrite U)
The darkish colour of phenolic resins, particularly when subjected to heat, meant that only sombre toned mouldings could be produced — notably black, and shades of brown. The search for a colourless resin with similar properties to phenolics, led to the development in the 1920,s / 1930’s of urea and thiourea resins. When combined with cellulose fillers and suitable colorants, the resins made possible the production of articles such as trays, cups, picnic-ware and lampshades in white and brilliant colours. Like mouldings made from phenolics, such items are keenly sought after by collectors who enthuse upon both the visually exciting simulations of alabaster and marble and the exotic trade names such as BEATL, BANDALASTA and LASTALONGA. As with the phenolic resins, however, the urea resins found important industrial applications in varnishes, laminates and adhesives.
Malamine Formaldehyde
With the development of melamine resins around the mid 1930’s, the family of thermosetting formaldehyde condensation resins was complete. The melamines closely resemble the urea formaldehyde plastics in their general properties and colour range, but they enjoyed more resistance to heat, water and detergents. The porcelain-type appearance of mouldings made it a particularly attractive material for moulding cups, saucers, plates and similar domestic items although they were more costly than similar items in urea formaldehyde.
Thermoplastics
With the start of the 1930’s came the ‘Poly’ era: the first of many thermoplastics was Polyvinyl Chloride. Originally observed in the 1870’s by Baumann, it did not become a commercial reality until suitable plasticisers were developed early in the 1930’s. At about the same time an American producer, Du Pont, launched the first polyamide —nylon 66 — perfected after minute analysis of the structure of silk by their chemist Wallace Carothers. Only a few months later German researchers succeeded in producing the first nylon6 from caprolactam. The major event in the UK came in 1935 when, after three years research, ICI Alkali Division laboratories produced polyethylene, the material whose dialectic properties were to be vital to wartime development of radar.
Another material with a lengthy gestation was polystyrene. Originally discovered in 1839 by a German apothecary Simon, it was another German, organic chemist Staudinger, who realised that the solid that Simon had isolated from natural resin was in fact composed of long chains of styrene molecules.
Commercial production still had to wait until 1937 before an economic way of preventing polymerisation during storage could be found. The other ICI development which made a vital wartime contribution was polymethyl methacrylate, more commonly called acrylic or ‘Perspex’. First produced commercially in the UK in 1934, its shatter-resistant properties were soon in vast demand for aircraft canopies and all kinds of protective screens.
Other materials Other developments of the 1935-1945 period were silicones, widely used as water repellents and in heat resistant paints, epoxy resins which have outstanding properties of adhesion and chemical resistance and polyester resins which combined with glass fibre offered a structural material for boat and car bodies. Since then new polymers have been introduced every few years including PTFE, polycarbonate, PET, polypropylene, polyurethane, ABS and acetal. Now researchers are combining resins both together and with fillers and reinforcing agents to produce the next generation of plastics materials.
High-Tech Plastics
Engineers and designers are becoming increasingly aware of the important position plastics play across a wide band of engineering applications. Advances in electronic and automotive engineering depend heavily on plastics. The aerospace industry would grind to a halt without advanced plastics composites.
New materials and new applications are being found almost daily.
The ability of plastics to be moulded to very complex shapes gives the designer the opportunity to design for assembly, to reduce overall cost and produce a more efficient end product. For the future, composites look set to play a most important role. Both thermoplastic and thermosetting plastics reinforced with glass, carbon and aramid fibres, have already made their mark on products from racing cars to tennis rackets.
The car of the future could well have a body made from reinforced plastics, springs made from glass reinforced plastics and plastics components in the engine. Though we may never see a practical all-plastics car, the world’s manufacturers are increasingly turning their attention to developing new mass production techniques in plastics.
In industry, advanced plastics and composites are everywhere replacing metal components in processes from food production to nuclear reprocessing. Plastics have revolutionised the sports goods, household appliance and electronics industries, and tissue compatible plastics, notably carbon fibre and PTFE, have made a great impact on the design of medical equipment and prostheses.
But it is the aerospace industry which still leads the way The 1980’s saw flight tests of the first ‘all plastics’ aircraft, the Beechcraft Starship 1, and the next generation of the ‘prop-fan’ engines for airlines. Most exciting of all is the proposed HOTOL sub-orbital space-craft which will continue man’s penetration of aerospace by tomorrow’s plastics.
