1 Materials Candidates should be able to: understand the physical and working properties in relation to using the common constructional materials, ie; plastics, woods and metals;  Plastic synthetic material: an extremely versatile synthetic material made from the polymerization of organic compounds. It can be moulded into shapes or fabricated in many different forms for use in commerce and industry.  Wood substance of trees: a hard fibrous substance that chiefly composes shrubs and trees and is found beneath their bark. Metal type of chemical element: a chemical element such as copper or iron that is usually solid in form, is usually a good conductor of heat and electricity, is malleable and ductile, and has a characteristic luster. Resistant Materials

2 Types of Materials Plastics (Real-World Technology Resistant Materials (RWTRM) pages 64 – 68) Candidates should be able to: show a working knowledge of the following: thermoplastic plastics - nylon, polythene, polyvinyl chloride (PVC), acrylic and polystyrene; thermosetting plastics - polyester resin including GRP, melamine, urea formaldehyde and phenol formaldehyde; Plastics, materials made up of large, organic (carbon-containing) molecules that can be formed into a variety of products. The molecules that compose plastics are long carbon chains that give plastics many of their useful properties. In general, materials that are made up of long, chainlike molecules are called polymers. The word plastic is derived from the words plasticus (Latin for “capable of moulding”) and plastikos (Greek “to mould,” or “fit for molding”). Plastics can be made hard as stone, strong as steel, transparent as glass, light as wood, and elastic as rubber. Plastics are also lightweight, waterproof, chemical resistant, and produced in almost any colour. More than 50 families of plastics have been produced, and new types are currently under development. Resistant Materials

3 Plastics Plastics are mouldable, synthetic (chemically-fabricated) materials derived mostly from fossil fuels, (oil, coal, or natural gas) trees (e.g. rubber) and plants (e.g. cellulose). The raw forms of other materials, such as glass, metals, and clay, are also mouldable. The key difference between these materials and plastics is that plastics consist of long molecules that give plastics many of their unique properties, while glass, metals, and clay consist of short molecules. Like metals, plastics come in a variety of grades. For instance, nylons are plastics that are separated by different properties, costs, and the manufacturing processes used to produce them. Also like metals, some plastics can be alloyed, or blended, to combine the advantages possessed by several different plastics. For example, some types of impact-resistant (shatterproof) plastics and heat-resistant plastics are made by blending different plastics together. Resistant Materials

4 Plastics Polymer, substance consisting of large molecules that are made of many small, repeating units called monomers, or mers. The number of repeating units in one large molecule is called the degree of polymerization.. Most of the organic substances found in living matter, such as protein, wood, chitin, rubber, and resins, are polymers. Many synthetic materials, such as plastics, fibres (Nylon; Rayon), adhesives, glass, and porcelain, are also to a large extent polymeric substances. A polyethylene molecule DNA molecule – a natural polymer Resistant Materials

5 Plastics Thermoplastic plastics These plastics are made up of lines of long chain molecules (right) with very few cross linkages. This allows them to soften when heated so that they can be bent into different shapes, and to become stiff and solid again when cooled. This process can be repeated many times. Long chain molecules Some examples Nylon Photo: Injection moulded gear wheels. Uses: Bearings, curtain rail fittings, combs, hinges, clothing, stockings, gear wheels and power tool casings. Resistant Materials

6 Thermoplastic plastics Polythene (High Density, HDPE) Photo: Blow moulded milk container. Uses: Bottles, pipes, bowls, milk crates and buckets. Polythene (Low Density, LDPE) Photo: Blow moulded drinks bottles. Uses: Packaging film, carrier bags, TV cable, toys, detergent 'squeezy' bottles and dip coating. Polyvinyl chloride PVC (Rigid) Photo: Injection moulded downpipe bend. Uses: Rainwater goods, pipes to carry air and water, window frames, chemical tanks, floor and wall coverings, shoe soles, shrink and blister packaging. Note: Rigid PVC has good weather resistance and is self extinguishing. Resistant Materials

7 Thermoplastic plastics Polyvinyl chloride PVC (Plasticised) Photo: Extruded hose pipe. Uses: Leathercloth, suitcases, dip coating, hose pipes, electrical wiring insulation, vinyl wallpaper, floor tiles, toys, dolls, footballs and cushioning (when foamed). Acrylic Photo: Cast acrylic car light cluster. Uses: Shop signs in the display industry, baths, machine guards, furniture, roof lights, glazing and car light lenses. Note: Acrylic scratches easily and tends to splinter. It can be polished to a high finish. Breakage resistance is 6-17 times greater than glass. Trade names: Perspex, Plexiglass. Resistant Materials

8 Thermoplastic plastics Polystyrene (High Impact) Photo: Injection moulded disposable razor. Uses: Low cost and disposable items produced by vacuum forming or injection moulding, internal secondary glazing, toys, model kits and refrigerator linings. Expanded Polystyrene Photo: Polystyrene decorations. Uses: Packaging, ceiling tiles and insulation. Note: Expanded polystyrene is lightweight and buoyant. It is a good sound and heat insulator. Normally white in colour. Expanded polystyrene crumbles easily which can be a disadvantage. Resistant Materials

9 Thermosetting plastics These plastics are made up of molecules which are heavily cross-linked (right). This results in a rigid molecular structure. Although they soften when heated the first time, and can therefore be shaped, they then become permanently stiff and solid, and cannot be reshaped. Cross-linked molecules Some examples Polyester Resin Photo: GRP children's ride. Uses: Laminated to form GRP (glass reinforced polyester), casting, encapsulating, car bodies and boats. Resistant Materials

10 Thermosetting plastics Melamine Formaldehyde Photo: Compression moulded bowl, mug and plate. Uses: Tableware, electrical insulation, synthetic resin paints and decorative laminates for work surfaces. Note: Melamine Formaldehyde is self extinguishing, odourless, strong, scratch and stain resistant. Urea Formaldehyde Photo: Compression moulded 'surge' protection plug. Uses: Electrical fittings, domestic appliance parts, textiles and wood adhesives. Note: Urea formaldehyde is strong but brittle. Phenol Formaldehyde Photo: Compression moulded light fitting. Uses: High strength fabrics, paper reinforced engineering laminates, dark coloured electrical fittings and parts of domestic appliances, bottle tops, knobs and door handles. Note: Phenol Formaldehyde is strong but brittle and is limited to dark colours. Resistant Materials

11 Plastics: Questions 1a) List four raw materials that are used in the making of plastics. ___________________________________________ ___________________________________________ b) What advantages and disadvantages do plastics have compared to wood? Advantages ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ Disadvantages ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ ___________________________________________ 2a) Briefly explain what a thermoplastic plastic is. _________________________________________________ _________________________________________________ _________________________________________________ _________________________________________________ b) Explain what a thermoset (or thermosetting) plastic is. _________________________________________________ _________________________________________________ _________________________________________________ _________________________________________________ Resistant Materials

12 Plastics: Questions Complete the table below Thermoplastic plastics MaterialProperties and working characteristicsUses Nylon (Polyamide) Polythene (High Density, HDPE) Polythene (Low Density, LDPE) Polyvinyl chloride PVC (Rigid) Polyvinyl chloride PVC (Plasticised) Acrylic Polystyrene (High Impact) Expanded Polystyrene Polypropylene Cellulose acetate Acrylonitrile butadienstyrene (ABS) Resistant Materials

13 Thermosetting plastics MaterialProperties and working characteristicsUses Polyester Resin Melamine Formaldehyde Urea Formaldehyde Phenol Formaldehyde Epoxy resin (epoxide) Plastics: Questions Complete the table below Resistant Materials