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Thermoplastics

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Thermoplastics
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Thermoplastics

  1. 1. CONSTRUCTION & MATERIALS THERMOPLASTICS
  2. 2. PLASTICS - INTRODUCTION • Material of “New age” • Its basic constituent is prepared synthetically or semi- synthetically from monomer. • Easily machined , cast and joined • Ease of manufacturing and versatility • hardness, elasticity, breaking strength, temperature resistance, thermal dimensional stability, chemical resistance • Properties • Low cost • ease of manufacture • Versatility • imperviousness to water • usually low melting point • electrical insulator (except stretch-oriented polyacetylene). • Some may decompose to toxic substances when heated.
  3. 3. PLASTICS HISTORY FİRST PLASTİC: PARKESİNE •The first man-made plastic was created by Alexander Parkes who publicly demonstrated it at the 1862 Great International Exhibition in London. •The material called Parkesine was an organic material derived from cellulose that once heated could be molded, and retained its shape when cooled.
  4. 4. SNAPSHOTS OF SOME PARKESINE MATERIALS (FIRST PLASTIC)
  5. 5. PLASTICS - CLASSIFICATION ELASTOMERS THERMOSETS THERMOPLASTICS
  6. 6. THERMOPLASTICS • A thermoplastic, also called a thermo-softening plastic is a plastic which becomes pliable or mouldable above a specific temperature and returns to a solid state upon cooling. • Most thermoplastics have a high molecular weight. • Polymers which moulds above Glass transition temperature and returns to normal state upon cooling. • CHARACTERISTIC: More aesthetically pleasing, Stronger and stiffer but lower toughness, expensive forming process, less resistance to mechanical creep, not suitable for use in extremely temperatures, little to no cross-linking in microstructure, eco-friendly forming process.
  7. 7. SNAPSHOTS OF THERMOPLASTICS
  8. 8. EXAMPLES OF THERMOPLASTICS
  9. 9. POLYVINYL CHLORIDE (PVC) • Polyvinyl chloride is produced by polymerization of the vinyl chloride monomer (VCM) • PVC comes in two forms, rigid -RPVC (for construction in pipe and in doors and windows) and are made more flexible by addition of plasticizers (phthalates). [Add ease of work, used for cables, lowers glass transition temperature, increased flexibility and durability]
  10. 10. PROPERTIES • Tough • lightweight material that is resistant to acids and bases. • High hardness • high modulus of elasticity (rigid-type), very low modulus of elasticity (flexible) • Poor heat stability, small expansion coefficient • Good flame retarding • Electrical insulator USES • Much of it is used by the construction industry, such as for vinyl siding, drainpipes, gutters and roofing sheets. • PVC pipes, electric cable insulation, uPVC in place of wood, signs, clothing, furniture • It is also converted to flexible forms with the addition of plasticizers, thereby making it useful for items such as hoses, tubing, electrical insulation, coats, jackets and upholstery. • Flexible PVC is also used in inflatable products, such as water beds and pool toys.
  11. 11. POLYETHYLENE • Polyethylene (polyethene, polythene, PE) is a family of similar materials categorized according to their density and molecular structure. • It’s the most common plastic, mixture of organic compounds. PROPERTIES: • Low strength • Hardness and rigidity • High ductility • Relatively low melting point • Corrosion resistant (from acids and bases) • Burns slowly with a blue flame The most important polyethylene grades are: UHMWPE, HDPE, MDPE, and LDPE.
  12. 12. 1)ULTRA-HIGH MOLECULAR WEIGHT PE (UHMWPE): • Tough and resistant to chemicals. USES: • manufacture moving machine parts • bearings gears • artificial joints • some bulletproof vests. 2) HIGH-DENSITY POLYETHYLENE (HDPE): • Density >= 0.941g/cm3. • Low degree of branching low tensile strength USES: • milk jugs • detergent bottles • garbage containers • water pipes.
  13. 13. 3)MEDIUM-DENSITY POLYETHYLENE (MDPE): • Density 0.926-0.940g/cm3. • Good shock and drop resistance • less notch sensitive than HDPE • stress cracking resistance is also better. USES: • gas pipes and fittings • sacks • shrink film • carrier bags. 4)LOW-DENSITY POLYETHYLENE (LDPE) • Density 0.910-0.940g/cm3, • lower tensile strength, increased ductility USES: • rigid containers • plastic film applications.
  14. 14. POLYPROPYLENE PROPERTIES • Tough & flexible • light weight & durable • used as an engineering plastic when copolymerized with ethylene • good resistance to fatigue • corrosion resistant & heat resistant • resilient to impact and freezing, can be joined by heat fusion USES • Plastic hinges, • as a dielectric, kettles, food containers, carpets, rugs, ropes, • PVC alternative • electrical cables • plastic mouldings (bottle tops, bottles, and fittings)
  15. 15. POLYMETHYLMETHACRYLATE (PERSPEX) • Shatter resistant which is also called acrylic glass PROPERTIES: • Moderate strength • easy handling and processing • low cost • prone to scratching USES: • Transparent glass substitute (submersibles, aircraft, riot control, aquariums) • daylight radiation • implants • acrylic paint
  16. 16. Materials – Plastics Thermoplastic Thermoplastic properties Thermoplastic uses Example outcomes Acrylics or Perspex (Polymethyl Methacrylate) Stiff, hard, shiny, brittle in small sections, durable, scratches easily, available in different colours, good electrical insulator Used for signs, key rings, lighting, storage containers High impact polystyrene (HIPS) Light but strong plastic, available in sheets in a variety of thicknesses and colours and softens at about 95 degrees Used for vacuum forming and making outer casings and packaging for products Acetate Hard, shiny and translucent/transparent Used in badge-making, packaging and for overhead projector transparencies Expanded polystyrene (styrofoam) White, lightweight and crumbly Used for protective or insulating packaging • Thermosetting – plastics that can only be heated and be moulded once. If re-heated they cannot soften. • Thermoplastics – plastics that are moulded by heating and can be remoulded if heated again. Thermoplastics soften when heated and can be shaped when hot. The plastic will harden as it cools down. SUMMARY
  17. 17. Materials – PlasticsThermoplastic Thermoplastic properties Thermoplastic uses Example outcomes Polypropylene (PP) Light, hard, flexible but can scratch easily. Durable to wear and has good resistance to chemicals Used for different kinds of packaging, chairs, gadgets, textiles and automotive components Low density polyethylene (LDPE) Soft, flexible, good resistance to chemicals, good electrical insulator, tough Used for packaging film, carrier bags, bottles, toys High density polyethylene (HDPE) Hard, stiff and strong. Able to be sterilised Used for plastic bottles, tubing and household equipment Corrugated plastic Lightweight, rigid and weatherproof Used for sign boards and folders Low-tack masking film Flexible and transparent Used to position sticky- backed vinyl letters or images onto a chosen surface. Used for creating signs, stencils and vehicle signage Polyvinyl chloride (PVC) Stiff, hard wearing, brittle but can be treated to make it softer and more rubbery Used for blister packs, window frames, records and clothing

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