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Materials (Including Composite and Smart Materials). Woods. Woods can be protected with finishes, this is needed especially if they are going to be used outdoors.
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Woods can be protected with finishes, this is needed especially if they are going to be used outdoors. • Wood stain will enhance the grain in wood. It comes available in natural colours but also in bright colours such as reds and blue. Wood stains wont always protect the wood so varnish would be used also. • Oils can help to maintain the woods natural appearance. Some oil based finishes will allow for protection outdoors. • Paint is often used to both colour and protect wood. Emulsion paints are cheaper but are water based so wont protect against water. • Polyurethane varnish can be used to seal and protect the surface of wood and give it a smooth surface finish. This can come clear or in a variety of colours. This is the best option for protecting the wood and allowing the natural appearance of the wood to be shown. Although wood is sustainable and new trees can be grown, it is best to reuse and recycle woods after use, to save the energy needed to process new trees into workable timbre. Woods
Heat treatements can soften or harden a metal material. • Annealing – this process involves heating the metal and leaving it to cool slowly making it softer, more ductile and less brittle. • Hardening – this involves heating metals and rapidly cooling them (in cold water or oil). This makes the metal harder but more brittle. This means the metal is often tempered. • Tempering makes the metal tougher and less likely to break. For example, when steel is tempered its cleaned (making it bright in appearance) and then gently heated. As the metal gets hotter it will gradually start to change colour with the colour being used to indicate how tough it has become. Metals can be finished for both protection and looks. • Painting – Primers such as red oxides and zinc chromates are needed for steel to allow for additional coats afterwards. The Golden Gate bridge has been protected red to prevent rusting and corrosion. • Plastic coating – A metal is evenly heated in an oven and then plunged into fluidised powder (very fine powder that’s made to act like a liquid by passing gas through it) for a few seconds. The metal can then be returned to the oven allowing the thin coating of plastic to fuse to the surface. • Polishing – done by hand or using a buffing wheel – the wheel is coated in abrasive polish (Rubs away the surface) and the metal is held against the spinning wheel until the required surface finish is achieved. (Chrome)
Thermoplastics and Thermosetting plastics can be bought in a number of different forms, for example powders, granules, pellets, and liquids. When processed they are available as films, sheets, rods, and tubes. Plastics don’t need surface finishes because they are resistant to corrosion and decay. Wet and dry paper can be used for a better quality finish, followed by a mild abrasive polish. Most plastics are made from crude oil, however new plastics are being generated that are made from substances found in plants. This will make the plastics more biodegradable and therefore more environmentally friendly. It is always better to recycle and reuse plastic as much as possible, as this means there is less need to make new plastic from oil, and used much less energy. Plastics
Composite materials: A composite material is a combination of two or more materials bonded together. This can make a material with more useful properties than either material alone. • GRP – Glass reinforced plastic, strands of glass fibres that have been coated in polyester resin. Can be moulded into shape, improves strength and toughness of the material. • Carbon fibre reinforced plastic, similar to GRP, carbon strands that have been coated in polyester resin. Stronger, tougher and lighter than GRP. • Kevlar, strong plastic materials woven to form a mat. Used in body armour, bullet proof vests for the army and police. Lighter and stronger than carbon reinforced plastic.
Smart Materials A smart material is a material that can change its properties when their environments change. Polymorph– plastic granules. When heated can change from a solid to a moldable state. Its shape can be changed when reheated. Good for ergonomic handles on children’s cutulary for example. Thermochromic– has the ability to change colour as the material changes temperature. Used in everyday technology such as Russell Hobbs kettles, Thermochromic inks are used in babies feeding spoons to ensure they are not to hot. Shape Memory Alloys– Can change shape when heated. Nitinolis used for teeth bracing, when heated the length shortens, pulling teeth back into shape. Memoflex spectacles can be bent and twisted and will regain its original shape.
