All about plastics

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  • Created by: Manyah
  • Created on: 25-04-20 13:58
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  • Plastics
    • What is a plastic?
      • A plastic is an material that can be shaped or molded into any form
    • What are they made from?
      • Plastics are mainly made of oil
        • Oil is a carbon-rich raw material, and plastics are large carbon-containing compounds
    • Can it react chemically?
      • Most plastic is chemically inert and therefore will not react with any other substances
      • This means that you can store alcohol, water, soap, acid or gasoline in a plastic container without it dissolving the container itself
    • How was plastic discovered?
      • First discovery
      • Second discovery
        • In 1846, Charles Schonbein, a Swiss chemist, accidentally discovered another polymer when he spilled nitric acid-sulfuric acid on some cotton
          • The resultant polymer, nitrocellulose, could burst into a smokeless flame and was used in the military as an alternative to gunpowder
            • In 1870, chemist John Hyatt reacted nitrocellulose with camphor to make celluloid, a plastic polymer
              • This was first used in photographic film, billiard balls, dental plates and ping pong balls
      • Third discovery
        • In 1909, chemist Leo Bakeland synthesized Bakelite, the first truly synthetic polymer from a mixture of phenol and formaldehyde
          • Bakelite can be molded when hot and solidified into a hard plastic that can be used for handles, phones auto-parts, furniture and jewelry
            • The invention of Bakelite led to a whole class of plastics with similar properties, known as Phenolic resins
      • Fourth discovery
        • In the 1930's, a DuPont chemist names Wallace Carruthers invented a plastic polymer made from the condensation of adipic acid  and some diaminohexane monomers that could be drawn out into strong fibers like silk
          • This plastic became known as nylon
    • Plastics can be separated into 2 major categories
      • Thermoplastics
        • Less rigid than thermosets, thermoplastics can soften upon heating and return to their original form
          • They are easily molded and extruded into films, fibers and packaging
            • Examples of these plastics include: polyethylene, polypropylene, polyvinyl chloride
      • Thermoset or Thermosetting plastics
        • Once cooled and hardened, these plastics retain their shapes and cannot return to their original form. They are hard and durable
          • Thermosets can be used for auto parts, aircraft parts and tires
            • Examples of these plastics include: polyurethane, polyesters, epoxy resins and phenolic resins
    • How are plastics made?
      • 1. Prepare raw materials and monomers
        • 2. Carry out polymerization reactions
          • 3. Process the polymers into final polymer resins
            • 4. Produce finished products
    • Processes used to create products out of plastic
      • Extrusion
        • Pellets are heated and mechanically mixed in a long chamber, forced through a small opening and cooled with air or water
          • This is used to make plastic films
      • Injection Molding
        • The resin pellets are heated and mechanically mixed in a chamber and then forced under high pressure into a cooled mold
          • This  process is used for containers like butter and yogurt tubs
      • Blow molding
        • This technique is used in conjunction with extrusion or injection molding. The resin pellets are heated and compressed into a liquid tube
          • The resin goes into the chilled mold , and compressed air gets into the tube, which expands the resins against the edges of the mold
            • This process is used to make hollowed items and bottles
      • Rotational molding
        • The resin pellets are heated and cooled in a mold that can be rotated in 3 dimensions. The rotation evenly distributes the plastic along the walls of the mold
          • This technique is used to create long, hollow plastic items such as toys, furniture and sports equipment
    • Bioplastics
      • Naturally occurring polymers such as starches, cellulose, soy protein, vegetable oil, triglycerides, and bacterial polyesters, can be extracted from crops and bacterias
        • Furthermore, plants and microorganisms can produce substances like lactic acid, which can be polymerized into bioplastics
      • Fermentation
        • Bacteria or other microorganisms mass-produce the bio-polymers in bioreactors /fermentation tanks
          • The bio-polymers are extracted from the bioreactors and chemically processed into plastics
      • Bioplastics have the advantage of being produced from renewable resources rather than non-renewable resources
        • Furthermore, bioplastics are biodegradable - they can break down in the environment, which means its a very important industry
    • Recycling
      • Once collected, plastics go through a variety of steps
      • Inspection to weed out contaminants and inappropriate types of plastics
        • Shredding and washing
          • Separation based on density
            • Drying
              • Melting
                • Draining through fine screens to remove more contaminants
                  • Cooling and shedding into pellets
                    • Selling back to plastic companies

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