IGCSE Plastics 1 PDF

Plastics: How plastics are used. Plastics are man-made materials that can be shaped into almost any form. They are one of the most useful materials ever created. Plastics...

Plastics: How plastics are used. Plastics are man-made materials that can be shaped into almost any form. They are one of the most useful materials ever created. Plastics have been developed that are as rigid as steel or as soft as cotton. They can be made in any colour or clear and colourless. They can be rubbery or rigid, and they can be shaped into an endless variety of objects, ranging from car bumpers to squeezable bottles to soft fabrics. Plastic products, especially those used by industries, often have a useful life of many years. Plastics consist of long chains of molecules called polymers. These chains are made of repeating patterns of smaller molecules. The chains can be rigid and are lined The chains can be flexible and They can have very strong up like logs flowing down a river. tangled like spaghetti on a plate. cross links These different structures give plastics their most notable characteristic, the ability to be shaped. In fact, the word plastic comes from the Greek word “plastikos”, which means able to be shaped. Plastics: How plastics are used. Plastics can replace metals, natural fibres and hides, paper, wood and stone, and glass and ceramics. Manufacturers use the different properties of plastics to make products that are Stronger; Lighter; Longer lasting; Easier to maintain and Less expensive to make Plastics are used to replace: Metals. Plastic parts are replacing metals in airplanes, cars, and many mechanical devices. Airplane manufacturers use plastic wing and body assemblies to reduce the weight of an aircraft, thereby reducing fuel consumption. Plastic car parts do not rust, nor do they dent as easily as metal ones. They are also easier and often less expensive to repair. Surgeons mend broken bones with plastic parts rather than metal ones, because the plastics are less likely to trigger a harmful reaction. Dentists often use plastic fillings because--unlike metal fillings--the plastic ones can match the patient's tooth colour. Plastics: How plastics are used. Plastics are used to replace: Natural fibres and hides. The textile industry uses plastics to replace such natural fibres as cotton, silk, and wool. Plastic fibres may have such qualities as strength, durability, and resistance to stains and wrinkling. Some plastic fibres are tough enough to be used for safety belts in cars or bullet-proof vests. Durability and resistance to stains make plastic fibres excellent for clothing, carpeting, and furniture coverings. Manufacturers can also treat plastic fibres to make them more difficult to burn. Kevlar is very strong and very light, weight for weight about five times as strong as steel. This is due to its chemical structure. Kevlar is a polymeric aromatic amide, an aramid. This means it is a polymer containing a benzene ring. Kevlar doesn’t burn easily because the ratio of carbon to Benzine ring – a closed chain of 6 hydrogen atoms is quite high it requires strong carbon atoms with hydrogen atoms concentrations of oxygen which leads to a low attached flammability. Plastics: How plastics are used. Plastics are used to replace: Paper. Plastics have replaced paper in many packaging applications. Plastic-foam packing materials provide more protection for boxed products than crushed paper does. Many fast-food restaurants use foamed plastic containers that help keep food warm. Wood and stone. Plastics have replaced wood and stone in many applications. Laminated plastic worktops come in a variety of patterns. Some look like marble. Laminated worktops are lighter, less expensive, and easier to install than marble ones. They also resist marring and stains. Glass and ceramics. Because they are lighter and far less likely to break, plastics have replaced glass or ceramics in a variety of products. Aeroplane windows made of acrylic plastics are lighter and less brittle than glass. Plastic bottles are shatterproof, and they have replaced glass ones in packaging many foods and household goods. Plastics: How plastics are used. To provide new characteristics. Plastics are used in many ways not possible for other materials. They have many medical applications because they are not harmful to the body and can be formed into any shape. Parts made from plastics can replace damaged hip, knee, and finger joints. Plastic pieces are used to rebuild facial structures damaged by accidents. Plastics can be used to replace glass in artificial eyes and can be used to save peoples lives when used as an artificial heart pump. As well as replacing the entire organ plastic can be used to replace worn out heart valves. Artificial plastic heart Thermoplastics Resin Identification Code The Society of the Plastics Industry, Inc. (SPI) introduced its resin identification coding system in 1988 at the urging of recyclers around the country. A growing number of communities were implementing recycling programs in an effort to decrease the volume of waste subject to rising tipping fees at landfills. Recycling firms have varying standards for the plastics they accept. Some firms may require that the plastics be sorted by type and separated from other recyclables; some may specify that mixed plastics are acceptable if they are separated from other recyclables; while others may accept all material mixed together. Not all types of plastics are generally recycled, and recycling facilities may not be available in some areas. Plastics Types of plastics. Although there are hundreds of different plastics, all of them belong to one of two basic types, based on how they behave when heated. These are: Thermoplastics Thermoplastics can be melted and re-formed. Their polymer chains do not form cross-links. Thermosetting plastics Thus, the chains can move freely each time the Thermosetting plastics--or thermosets, for plastics are heated. Manufacturers use short--can be heated and set only once. They thermoplastics more than thermosets because cannot be re-melted or reshaped. When a thermoplastics are easier to handle. thermoset is heated, it undergoes a chemical reaction called cross-linking, which binds its Because their molecules can slide slowly past polymer chains together. Because thermosets one another, some thermoplastics tend to lose cannot be re-melted, engineers use them in their shape when exposed to constant pressure applications that require high resistance to heat. over a long period of time. Thermoplastics Polyethylene Terephthalate (PET or PETE) PET is clear, tough and has good gas and moisture barrier properties. The vast majority of this plastic ends up in soft drink bottles and blow moulded containers, although sheet applications are increasing. In addition, a small volume of PET is now used outside the packaging industry for the production of injection moulded components such as bicycle mud guards. Cleaned, recycled PET flakes and pellets are in great demand for spinning fibre for carpet yarns and producing fibrefill and geotextiles. Other outlets include strapping, moulding compounds and both food and non-food containers. Qualities: Uses: Recycled Products: Clarity, strength/toughness, barrier to Plastic soft drink bottles, mouthwash Tote bags, dishwashing liquid gas, resistance to grease/oil, stiffness, bottles, peanut butter and salad containers, laser toner cartridges, resistance to heat. dressing containers. picnic tables, hiking boots, lumber, mailbox posts, fencing, furniture, sweatshirts. Thermoplastics High Density Polyethylene (HDPE) HDPE is a relatively straight chain structure, but, as its name implies, exhibits a higher density. It is naturally milky white in appearance and finds wide application in blow moulded bottles for milk, water and fruit juices. Copolymer HDPE, pigmented with a variety of colorants, is used for packaging toiletries, detergents and similar products. Qualities: Uses: Recycled Products: Stiffness, strength/toughness, low cost, Milk, water and juice containers, Recycling bins, benches, bird feeders, ease of forming, resistance to grocery bags, toys, liquid detergent retractable pens, clipboards, fly chemicals, permeability to gas, ease of bottles. swatters, dog houses, vitamin bottles, processing. floor tile, liquid laundry detergent containers. Thermoplastics Vinyl (Polyvinyl Chloride or PVC) In addition to its good physical properties, PVC has excellent transparency, chemical resistance, long-term stability, flammability resistance, good weather ability, flow and insulator electrical properties. The diverse slate of vinyl products can be broadly divided into rigid and flexible materials. Rigid applications, accounting for 60 percent of total vinyl production, are concentrated in construction markets which include pipe and fittings, siding, carpet backing and windows. Bottles and packaging sheet are also major rigid markets. Flexible vinyl is used in wire and cable insulation, film and sheet, floor coverings, synthetic-leather products, coatings, blood bags, medical tubing and many more applications. Qualities: Uses: Recycled Products: Versatility, ease of blending, Clear food packaging, shampoo Air bubble cushioning, flying discs, strength/toughness, resistance to bottles. decking, film, panelling, recycling grease/oil, resistance to chemicals, containers, roadway gutters, clarity, low cost. snowplough deflectors, playground equipment. Thermoplastics Low Density Polyethylene (LDPE) A plastic used predominantly in film applications due to its toughness, flexibility and relative transparency. Because of its lower melting point at a given density, it is used in applications where heat sealing is easily accomplished. LDPE is the preferred resin on older unconverted film extrusion equipment due to its ease of extrusion. Typically, LDPE is used to manufacture flexible films such as those used for plastic retail bags and garment dry cleaning and grocery bags. LDPE is also used to manufacture some flexible lids, and it is widely used in wire and cable applications for its good insulatory electrical properties and processing characteristics. Qualities: Uses: Recycled Products: Ease of processing, barrier to moisture, Bread bags, frozen food bags, grocery Shipping envelopes, garbage can strength/toughness, flexibility, ease of bags. liners, floor tile, furniture, film, compost sealing, low cost. bins, paneling, trash cans, landscape timber, mud flaps. Thermoplastics Polypropylene (PP Polypropylene has excellent chemical resistance, is strong and has the lowest density of the plastics used in packaging. It has a high melting point, yet is readily heat-sealable. In film form it may or may not be oriented (stretched). It is also relatively inexpensive. PP is found in everything from flexible and rigid packaging to fibers and large molded parts for automotive and consumer products. Qualities: Uses: Recycled Products: Strength/toughness, resistance to Ketchup bottles, yogurt containers and Signal lights, battery cables, brooms chemicals, resistance to heat, barrier to margarine tubs, medicine bottles. and brushes, ice scrapers, oil funnels, moisture, low cost, versatility, ease of landscape borders, bicycle racks. processing, resistance to grease/oil. Thermoplastics Polystyrene (PS) Polystyrene is a very versatile plastic that can be rigid or foamed. General purpose polystyrene is clear, hard and brittle. On a per-pound basis, it is a very inexpensive resin. It is a rather poor barrier to oxygen and water vapour and has relatively low melting point. Typical applications include protective packaging, containers, lids, bottles, trays and tumblers. Qualities: Uses: Recycled Products: Versatility, insulation, ease of Videocassette cases, compact disc Thermometers, light switch plates, processing, low cost, clarity. jackets, coffee cups, knives, spoons insulation, egg cartons, vents, desk and forks, cafeteria trays, grocery store trays, rulers, license plate frames. meat trays and fast-food sandwich containers. Thermosetting plastics Melamine Formaldehyde Qualities: Uses: Recycled Products: self extinguishing, Tableware, electrical Can be ground into odourless, strong, insulation, synthetic powder and used as scratch and stain resin paints and a filler in resins. resistant. decorative laminates for work surfaces. Melamine Formaldehyde Photo: Compression moulded bowl, mug and plate. Polyester Resin Qualities: Uses: Recycled Products: Can be layered to Laminated to form Can be ground into provide strength in GRP (glass powder and used as all directions. reinforced polyester), a filler in resins. Strong, easily casting, moulded and encapsulating, car shaped. bodies and boats. Photo: GRP children's ride. Thermosetting plastics Urea Formaldehyde Qualities: Uses: Recycled Products: Hardwearing, Electrical fittings, Can be ground into extremely good domestic appliance powder and used as electrical resistance. parts, textiles and a filler in resins. strong but brittle wood adhesives. Photo: Compression moulded 'surge' protection plug. Phenol Formaldehyde Qualities: Uses: Recycled Products: Hardwearing, High strength fabrics, Can be ground into extremely good paper reinforced powder and used as electrical resistance. engineering a filler in resins. strong but brittle. laminates, dark Limited to dark coloured electrical colours. fittings and parts of domestic appliances, bottle tops, knobs and door handles. Photo: Compression moulded light fitting.