CHALLENGE
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MATERIALS
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ALUMINIUM Aluminium is a strong, lightweight, silver-white, ductile and malleable, metallic element, symbol Al. It is the third most abundant element in the Earth's crust and by far the most abundant metal on Earth. It is an excellent conductor of electricity and oxidizes easily making it highly resistant to tarnish. Aluminium comes from the word alumen, which is the Latin name for alum. Aluminium Sulphate (commonly known as alum) |
Alum |
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TITANIUM Titanium is a strong, lightweight, silver-grey, metallic element which is resistant to corrosion, symbol Ti. It is the ninth most abundant element in the Earth's crust, its compounds occur in practically all igneous rocks and their sedimentary deposits. The element was discovered in 1791 by English mineralogist William Gregor and was named by German chemist Martin Klaproth after Titan one of the giants of Greek mythology. It was not obtained in pure form until 1925. Titanium is the most bio-compatible of all metals due to its total resistance to attack by body fluids, high strength and low modulus. Titanium is widely used for implants, surgical devices, and pacemaker cases. Titanium replacements for hips and other joints are well established and have been in use for over 30 years. Advanced coatings are now available which hasten the bonding of titanium with adjacent bone. |
Molecular structure of Titanium |
Titanium is used for its excellent corrosion and erosion resistance, high heat transfer efficiency, and superior strength-to-weight ratio. The bio-compatibility and strength of titanium make it an ideal material for dental posts and other oral prosthetics. Bone naturally adheres to the surface oxide of titanium without additional coatings. |
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GLASS Glass is a transparent or translucent substance that is physically neither a solid nor a liquid. Although glass is easily shattered, it is one of the strongest substances known. It is made by fusing certain types of sand. |
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Molecular structure of Silicone Rubber
Polyethene Atoms |
POLYETHENE Polyethene is a tough white, translucent, waxy thermoplastic (which means it can be repeatedly softened by heating). Polymer of the gas ethylene (technically called ethene, C2H4). It is used for packaging, bottles, toys, wood preservation, electric cable, pipes and tubing. Polyethylene is produced in two forms: low-density polyethylene, made by high-pressure polymerization of ethylene gas, and high-density polyethylene, which is made at lower pressure by using catalysts. This form, first made 1953 by German chemist Karl Ziegler, is more rigid at low temperatures and softer at higher temperatures than the low-density type. Polyethylene was first made in the 1930s at very high temperatures by ICI. In the UK it is better known under the trademark Polythene. |
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POLYTETRAFLUOROETHYLENE (PTFE) PTFE is used in a wide variety of permanent implants from vascular grafts to coatings on sutures and other materials. There is a decades long history of use of PTFE: it is considered to be inert and benign in the body. Some major permanent implant uses of PTFE are given below. According to the estimates approximately 85 % by weight of the PTFE resin used for permanent implants is used for lifesaving implants. MAJOR IMPLANT APPLICATIONS
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POLYESTER Polyester is a synthetic resin formed by the condensation of polyhydric alcohols with diabasic acids. Polyesters are thermosetting plastics used in making sythentic fibres and constructional plastics. |
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NYLON Nylon is a synthetic long-chain polymer. Nylon was the first all-synthesised fibre, made from petroleum, natural gas, air, and water. It is used in the manufacture of medical sutures. Nylon fibres are stronger and more elastic than silk and are relatively insensitive to moisture and mildew. |
The manufacture of carbon fibre |
CARBON FIBRE Carbon fibre is a fine, black, silky filament of pure carbon produced by heat treatment from a special grade of Courtelle acrylic fibre and, used for reinforcing plastics. The resulting composite is very stiff and, weight for weight, has four times the strength of high-tensile steel. It is used in the aerospace industry, cars, and electrical and sports equipment. |
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POLYMETHYLMETHACRYLATE (PMMA) - PERSPEX Perspex is the trade name for a clear, lightweight, tough plastic first produced 1930. It is widely used for watch glasses, advertising signs, domestic baths, motorboat windscreens, aircraft canopies, and protective shields. Its chemical name is polymethylmethacrylate. |
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PLASTICS Plastics are any of the stable synthetic materials that are fluid at some stage in their manufacture, when they can be shaped, and that later set to rigid or semi-rigid solids. Plastics today are chiefly derived from petroleum. Most are polymers, made up of long chains of identical molecules. Since plastics have afforded an economical replacement for ivory in the manufacture of piano keys and billiard balls, the industrial chemist may well have been responsible for the survival of the elephant. Most plastics cannot be broken down by microorganisms, so cannot easily be disposed of. Incineration leads to the release of toxic fumes, unless carried out at very high temperatures. Processed by extrusion, injection-moulding, vacuum-forming, and compression, plastics emerge in consistencies ranging from hard and inflexible to soft and rubbery. They replace an increasing number of natural substances, being lightweight, easy to clean, durable, and capable of being rendered very strong for example, by the addition of carbon fibres for building aircraft and other engineering projects. Thermoplastics soften when warmed, then re-harden as they cool. Examples of thermoplastics include polystyrene, a clear plastic used in kitchen utensils or (when expanded into a 'foam' by gas injection) in insulation and ceiling tiles; polyethylene (polythene), used for containers and wrapping; and polyvinyl chloride (PVC), used for drainpipes, floor tiles, audio discs, shoes, and handbags. Thermosets remain rigid once set, and do not soften when warmed. They include Bakelite, used in electrical insulation and telephone receivers; epoxy resins, used in paints and varnishes, to laminate wood, and as adhesives; polyesters, used in synthetic textile fibres and, with fibreglass reinforcement, in car bodies and boat hulls; and polyurethane, prepared in liquid form as a paint or varnish, and in foam form for upholstery and in lining materials (where it may be a fire hazard). One group of plastics, the silicones, are chemically inert, have good electrical properties, and repel water. Silicones find use in silicone rubber, paints, electrical insulation materials, laminates, waterproofing for walls, stain-resistant textiles, and cosmetics. PolyAmides are widely used for the production of film, sheet, and injection-moulded articles. Nylon, the first polyamide, was synthesized in 1934 by Wallace Carothers at the du Pont laboratories in the USA and was intended to have many of the properties possessed of natural silk. Although it does have other applications, nylon is known principally for its applications in the textile field. Nylon yarn, once it has been stretched during the filament-forming process, has a combination of properties unique among textile fibres. One of the most notable is remarkable tensile strength, combined with lightness in weight and a high degree of resilience. shape-memory polymers.
temperature falls. Biodegradable plastics are increasingly in demand: Biopol was developed in 1990. Soil microorganisms are used to build the plastic in their cells from carbon dioxide and water (it constitutes 80% of their cell tissue). The unused parts of the microorganism are dissolved away by heating in water. The discarded plastic can be placed in landfill sites where it breaks back down into carbon dioxide and water. It costs three to five times as much as ordinary plastics to produce. Another plastic digested by soil microorganisms is polyhydroxybutyrate (PHB), which is made from sugar. |
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