Chemistry - Material Choices - Physical Properties & Uses of Important Thermoplastic Polymers.

Type Properties and Characteristics Uses
Polyethylene ('Polythene') One of the most versatile thermoplastics. It is tough and flexible over a wide temperature range with good dimensional stability. Easily moulded. Good resistance to most common solvents. It has good weathering properties but with some deterioration on long exposure to light. Packaging as bags and bottles. Household goods such as bowls, buckets and many other containers. Piping, chemical equipment and coating for cables and wires.
Polypropylene Similar to polythene but has better heat resistance. It has good mechanical properties and excellent resistance to chemical attack by acids, alkalis and salts even at high temperatures. It is tough, rigid and light in weight. It is used for hospital and lab equipment, chemical plant and also domestic hardware. Sheets which are used in packaging, filter cloths and fishing nets. Monofilaments used as ropes.
Polystyrene Tough dense plastic, hard and rigid with good dimensional stability. Moulds with a high surface gloss. It has good strength but is inclined to be brittle due to high Tg. Retains properties at low temperatures. Attacked by petrol and other organic solvents. It can be foamed to produce rigid but very light cellular material. Used to make refrigerator trays,boxes. Rigid foams which are used in building and refrigeration as insulation against heat and sound. For example: ceiling tiles, buoyancy equipment and in packaging for insulation against shock.
Polyvinyl alcohol Tough, strong and flexible. It is resistant to many common organic solvents .Dissolves slowly in boiling water. It softens above 100°c. Processed by moulding, extrusion and solution coating. In water the solution can be used for sizing fabrics and papers. Also in adhesives. High solubility in water which limits its use.
Polyvinyl chloride (PVC) Unplasticised form - hard and rigid. If plasticised it becomes soft, flexible and rubbery. It has good dimensional stability with good resistance to water, acids, alkalis and most common solvents. Plasticised material stiffens with age. Rigid form used in mouldings of all kinds. Flexible form used in imitation leather cloth, raincoats, table cloths etc. Piping, electrical cable covering, guttering. Safety helmets and chemical tank linings.
Polyvinyl acetate (PVA) Soft. Poor dimensional stability. Good adhesive properties. It is resistant to water but dissolves in many common organic solvents. As it is soluble in many organic solvents it is used in paints, lacquers, adhesives and coatings.
Polyvinyl acetate/chloride Tough and more flexible than PVC, with good dimensional stability. Good resistance to acids, alkalis and most common solvents. Good electrical insulation. Unplasticised sheet is used for packaging. Uses include upholstery, chemical equipment and covering for wires and cables.
Polytetrafluoroethylene (PTFE or 'Teflon') Tough and flexible. Excellent heat resistance. It does not burn and is not attacked by any known reagent and no known solvent. Excellent electrical insulation. It has a waxy surface and low coefficient of friction. It is quite expensive. Fuel hoses, bearings, tapes and gaskets. Non-stick coatings for frying pans and other cooking utensils. It is also used in the chemical industry because of its resistance to attack.
Polyvinylidene chloride Very strong and tough. It is flexible with good resistance to attack by acids and alkalis and most organic solvents. It has excellent weather resisting properties. Outdoor furniture fabrics, food wrapping, seat coverings, chemical equipment, screens filters and wire coating.
Polymethyl Methacrylate (PMM or 'perspex') Excellent transmission of light. It is strong and rigid. Easily scratched. It softens in boiling water but is unattacked by most household chemicals. Attacked by petrol and many organic solvents. Provides good electrical insulation. Dentures, lenses, telephone, handles ,aircraft windows, sinks, lighting fittings, building panels, baths, protective shields, dials, corrugated roof lights, advertising displays. Adhesives and surface coatings.
Acrylonitrile-butadiene-styrene (ABS) High impact value, with high strength. Resistant to the impact of flying stones. High dimensional stability over widely differing conditions. It remains tough at sub-zero temperatures. Resists attack by acids, alkalis and many petroleum type liquids. Protective helmets, pipes, valves, refrigerator parts, water pumps, battery cases, tool handles. Used in the car industry, due to its high impact value. It can be chromium plated.
Polyamides (nylons) Tough and very strong. It is flexible and has a good resistance to abrasion. It has a good dimensional stability. It absorbs water but has good resistance to most common solvents. Deteriorates with long exposure outdoors. Has good electrical insulation. A number of different varieties are in use. Valves, gears, electrical equipment, handles, cams, bearings, shock absorbers. Surgical and pharmaceutical packaging .Filaments for bristles, fishing lines, climbing ropes and textiles.
Polyesters (thermoplastic types) Highly crystalline but if quenched from a melt to below Tg an amorphous structure results. Crystallises if annealed at above Tg. It is used as fibre or film and is strong and stable. Has good dimensional stability and resistance to many organic solvents. Attacked by strong acids and alkalis. Excellent electrical insulation. Widely used as a textile fibre ('Terylene', 'Dacron') Used in the electrical industries as insulation. Drums and loud speaker cones, drafting materials, book covering, packaging. Gaskets, mould release foils, insulating tapes.
Acetals (polyformaldehyde or polyoxymethylene) Strong and stiff. Creep resistant with good fatigue endurance. High crystallinity and high melting point make it suitable for replacing some metals. Good electrical properties and resistant to alkalis and many solvents. Attacked by mineral acids .Slight water absorption. It is adversely affected by prolonged exposure to ultra-violet light and is not recommended for outdoor use or in strong sunlight. Housings, impellors and other parts for water pumps, washing machines and extractor fans. Instrument panels and housings for cars. Also used for plumbing fittings, pipe clips, bearings, cams and gears. Window catches and hinges and parts for aerosol containers.
Polycarbonates Good impact strength and heat resistance with good dimensional stability. resistant to oils and most solvents. The surface takes a high gloss. Electronic equipment, aircraft parts and fittings for cars.
Polyurethanes (thermoplastic types) Physical properties of thermoplastic varieties are similar to nylon with good dimensional stability. Tough and strong. Low water absorption and resistant to most common solvents. Packaging film, textile coatings, tank linings, surgical gloves, gears and hosing.
Cellulose nitrate Tough and flexible. Easily worked and softens in boiling water. Has good resistance to water but dissolves in some organic solvents , such as alcohol, ketones and esters. It is not suitable for exposure outdoors. Its extreme inflammability limits its use now that many more suitable compounds are available. Solutions are used for leather cloth and lacquers. Used to make handles, spectacle frames, brushes, windows, piano keys, drawing instruments, pens and pencils and handle grips.
Cellulose acetate Tough and durable. It has good impact strength. Has high absorption of water which affects dimensions. Not suitable for outdoor use. It softens in boiling water and is resistant to most household chemicals. Attacked by acids, alkalis and alcohol. Toys, containers, machine guards, spectacle frames, book covers, packaging, insulation, steering wheels, oil pumps, buttons, door handles.
Cellulose acetate/butyrate Tough and flexible. Has better resistance to water than the acetate with better dimensional stability. It softens in boiling water and is resistant to most household chemicals but not organic solvents. Advertising displays, machine guards, Handles for brushes and cutlery, pens and pencils.
Ethyl Celluloses Tough and flexible with good impact strength at low temperatures. Good dimensional stability. Low absorption of water and good resistance to acids and alkalis. Dissolves in many organic solvents. Not suitable for outdoor use. Good electrical insulation. Packaging, handle and grip covers. Special hoses, telephones, car fittings, tool handles, vacuum cleaner parts, strippable protective coatings.

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