Materials Revision Metals, Plastics, and Woods This powerpoint runs through materials and their properties, fixing methods (temporary and permanent), and finishing techniques

Metals can be broken down into two main categories: Categories of metals Non-ferrous Metals don’t contain iron aluminium, copper, tin and lead are all non- ferrous. Ferrous Metalscontain iron will corrode unless protected attracted by a magnet.

Alloys A mixture of two or more metals Brass is an alloy of 65% copper and 35% zinc High tensile steel is an alloy of low carbon steel and nickel Stainless steel is an alloy of steel, chromium, nickel and magnesium. Categories of metals

Materials can be joined temporarily or permanently. Three methods of joining metals are shown below. Joining metals Riveting Nut, bolt & washer MIG Welding

Working with metals – finishing techniques Several surface finishing techniques can be used on metals. The most common ones are detailed below: Paint Plastic Coating Lacquering Enamelling Surface must be smooth & de- greased Primer required Hammerite is a good one-coat metal paint. Suitable for most metals Object is heated and dipped in a tank of powder paint Object is returned to oven to ensure a smooth, glossy finish. Helps to prevent corrosion after polishing A layer of cellulose or varnish is applied Often used on jewellery. Powdered glass is melted onto the metal surface Provides a hard (but brittle) finish with different colours and textures.

Plastics can be broken down into two categories: thermoplastics and thermosets. Categories of plastics Thermoplastics Soften when heated Can be reshaped More commonly used in schools Thermosets Initially set by heat Cannot be reshaped once set Extremely strong and durable

Plastics have an extremely wide range of uses. Here are some common products made from thermoplastics. Uses of plastics (thermoplastics) Acrylic High Density Polyethene Polystyrene ABS Low Density Polyethene Polypropene

Thermosets have different qualities to thermoplastics. Here are some uses for thermosets. Uses of plastics (thermosets) Melamine formaldehyde Urea formaldehyde GRP Phenol formaldehyde Epoxy resin

Working with plastics – other processes Plastics can also be worked in other ways. Buffer Oven Scroll Saw Drill Hot wire strip heater

Materials can be joined temporarily or permanently. Three methods of joining plastic are shown below. Joining plastics Nut, bolt and washer Riveting Adhesive

Working with plastics – finishing techniques Plastics have excellent surface qualities. As they are self-finishing, plastics require little or no surface finish. However, when designers want a specific colour or texture, spray paints can be used. Use wet and dry paper (wet) to smooth the surface down and create a ‘key’ for the primer to grip to. Primer is used to create an undercoat to protect the plastic and provide a good surface finish for the top coat. The primer should be rubbed down using wet and dry paper between coats. Top coat is applied once the primer has completely hardened. There are different surface textures: gloss, matt and metallic being the most common. Top coat is applied in several layers to build up a thick, tough surface layer on the top of the primer.

Timbers can be broken down into three categories: Categories of timbers Hardwoods come from deciduous trees can be very expensive. Softwoods come from coniferous trees grow in colder climates. Manufactured boards available in sheet form user friendly.

A closer look at hardwoods

A closer look at softwoods

A closer look at manufactured boards

Working with timber – other processes Timber can also be worked in other ways. Scroll Saw Drill Belt Sander Wood Lathe

Materials can be joined temporarily or permanently. Two methods of joining timbers are shown below. Joining timbers Screws Nails Can you think of any other methods?

Working with timber – finishing techniques Timbers can be treated with several surface finishes. They have different purposes and are chosen depending on where the product is going to be used and what type of visual appearance is desired: Paint Stain Wax Varnish Indoor and outdoor use Wood is sealed with a primer first Coats the surface of timber Cost effective Enhances the grain Penetrates the surface of timber A variety of colours is available Gives a dull gloss shine Enhances the grain Surfaces must be sealed Tough surface develops Resistant to heat and water Can be coloured