The term 'plastic' is ambiguous. Literally, it means a material that is malleable (can be shaped without breaking), and can be engineered and molded by flow (the raw material is liquid during manufacture). However, 'plastic surgery' does not refer to the use of materials, but rather emphasises the malleable aspect of plastic, in the reshaping of flesh.
The general use of the word 'plastic' is for a broad range of materials. These consist of large, long-chain molecules, which are organic polymers, and are usually synthetic, with high molecular mass. The large range of plastics have different properties, such as hardness, malleability, elasticity, resistance to temperature and chemicals, which can be controlled by the manufacturing process, and the additives. There are three main sub-groups of plastics: thermoplastics, duroplasts, and elastomers. The raw substance from which plastic is made is typically petrochemical in origin, although biosynthetic plastics can be derived from non-fossil sources, such as natural plant oils.
In 1844, Charles Goodyear finalised his technique for vulcanizing rubber, and industry embarked on a revolution in materials made to order.
In 1856, the metallurgist Alexander Parkes produced Parkesine. Prompted by a competition to find a substitute for ivory for billiard balls, he had treated cellulose with nitric acid to produce cellulose nitrate (pyroxilin), which, when dissolved in alcohol, hardened into a transparent elastic material. It was pigmented so that it would resemble ivory. It was registered as Celluloid in 1870, and, being a thermoplastic, could be moulded to any shape, from dentures to movie camera film.
However, it was not until 1907 that the first fully synthetic plastic was commercially produced. Leo Baekeland invented the term 'plastics' for his new 'bakelite'. Once the advantages of plastics over traditional materials, such as wood, stone, leather, metal, glass and ceramics, for household and other goods, had been realised, the plastics industry leapt upon every new polymer the chemists could produce.
Development in the 1920s and 1930s led to synthetics with enormous commercial potential, not only as a cheaper alternative to traditional materials, but materials, such as nylon, which made entirely new products possible. World War Two provided a stimulus for the mass-production of plastics, such as acrylic glass as an alternative to silicate glass for airplane windscreens.
By the 1950s, mass production of products made from plastics like polystyrene (PS) and polyvinyl chloride (PVC) transformed the consumer manufacturing industries. By the 1980s, the world was producing trillions of plastic bags for throw-away shopping conveniences, and packaging still accounts for as much as 40% of plastic use.
Wallace Carothers was an American chemist and pioneer in pure research into large-molecular weight polymers.
As a result, the love affair with the new materials grew into a nightmare, as millions of tonnes of discarded plastic waste entered the biosphere. Its characteristic of durability and non-degradability, so treasured by the manufacturing industry, was a cause of enormous concern for the environment. The natural world does not know what to do with unnatural products.
Reclaiming value from plastic waste is a very important issue in modern waste management. Up to 20% of plastic by mass can be additives to modify the properties of the basic carbon polymer chain. These additives, such as highly toxic organotin, create complications for effective waste management.
Plastic is cheap to produce, light and easily stored. It makes airtight, hygienic and tough containers, and strong, lightweight carriers, so is ideal for packaging, storage and transport. Plastic production uses 8% of the world oil production, which is 7 million barrels a day. Half of this oil is for feedstock in the production of plastic, and half is consumed in the production process itself. Reducing the amount of plastic produced will reduce energy consumption and emissions of carbon-dioxide (CO2), nitrogen-oxide (NO) and sulphur-dioxide (SO2) during manufacture, and reduce non-biodegradable landfill waste.
There are three basic ways to ensure the most is obtained out of plastic:
It is unlikely that plastic will ever be 100% recycled or reclaimed, at least not in the foreseeable short-term. Therefore, degradability of plastic is the next best option, ensuring that if the plastic ends up in a landfill, or worse, in the environment, it will degrade on a timescale which reduces the danger to wildlife, and nuisance to humans, considerably.
Bio-plastics are synthetic polymers made from plants, sugars, or plastic which is grown within genetically modified plants and micro-organisms. The use of bio-plastic avoids the use of non-renewable fossil fuel as feedstock, and also reduces risks from chemical additives in standard plastics. Toy manufacturers have begun to switch over to bio-plastics for health and safety reasons.
Acrylonitrile butadiene styrene, used for electronic equipment casings, computer monitors, printers, and drainpipes
Polypropylene, yoghurt tubs, drinking straws, bottle caps, many appliance casings, car bumpers, piping
Polyethylene, [(C2H4)n], used for supermarket bags, plastic bottles, and many other packagings and uses
High-density polyethylene, used for milk jugs, detergent bottles, molded containers
Low-density polyethylene, used for shower curtains, floor tiling, skirting boards
Polyvinyl chloride, used for plumbing piping, shower curtains, window frames and flooring
Polyvinylidene chloride, used for food packaging
Polystyrene, used for packaging foam, food containers, plastic tableware, CD cases
Polyamide, used for toothbrush bristles, fishing lines, fibres
Polycarbonate, used for CDs, riot shields, break-resistant windows, traffic lights, lenses
Polyethylene terephthalate, used in carbonated drinks bottles, non-glass jars, plastic film, microwave packaging
Polyurethane, very common plastic, used for cushion foam, insulation, car parts
Polyepoxide, used for adhesives, electronic component pots, and in composite materials, such as with hardeners
Polymethyl methacrylate (acrylic), perspex, plexiglas, hard contact lenses, glazing
Silicon is a heat resistant resin, used as a sealant in bathrooms, cooking utensils, and in paint
Polyester, used in fibers and textiles
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1916 - 2004
Francis Crick was a physicist who worked with molecular biologist James Watson to discover the structure of the DNA molecule in 1953. Their work heralded the 'coming of age' of the biological sciences, and permitted the later breaking of the 'code of life'.
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