Polymers

1
Polymers

• By Si Man Lam
• Date June 7, 2005

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What is a Polymer?

• Polymers are commonly known as plastics
• Long chain of carbon molecules with repeating
  units joined by covalent bonds
• Each repeating unit known as a monomer
• Polymer is Greek for many parts
• Imagine a bowl spaghetti that is how the
  molecular arrangement of polymers looks

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Two Groups of Polymers

• Thermoplastic
• Soften with heat and harden with cooling
• Examples HDPE, LDPE, PET
• Thermosets
• Cured or Hardened with heating
• Examples Bakelite, Epoxy, Polyurethane

4
Natural Polymers

• Existed since the beginning of time
• Examples include shellac, turtle shells and
  horns, latex, silk
• Chemically modified natural polymers include
  rubber and gun cotton

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World War II Revenge of the Synth

• Reduced supply of natural sources of latex, wool,
  silk and other materials
• Emergence of synthetic polymers
• Increased usage and development of nylons,
  acrylics, neoprene, polyethylene

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Bakelite

• Developed in 1907 by Leo Baekeland
• First synthetic polymer and first widely
  manufactured plastic
• At that time used to make everything from
  telephones and radios to auto parts, furniture,
  and jewelry

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Polyethylene

• Simplest and most basic polymer chain
• Made up of a long chain of Ethane molecules
  (CH3-CH3)
• Monomer form is Ethylene (CH2CH2)
• Available in Low Density and High Density
  Variations
• Commonly used for milk bottles, medicine bottles,
  bags, Toys

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PET

• Polyethylene Terephthalate
• Derivative of polyethylene with terephthalate
  molecule included in the chain
• Durable and clear properties with oxygen and
  water barrier
• Great for soda bottles and drink containers

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Teflon

• PolyTetraFluoroEthylene
• Discovered by Accident by Roy Plunkett at Dupont
  in 1938
• Secret Weapon of WWII - used to coat bearings and
  metal surfaces to reduce friction and wear and
  tear
• Now used for non stick pots and pans and dental
  floss

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Other Commonly Used Polymers

• Polypropylene (Microwavable Containers)
• Polyvinylchloride (Water pipes)
• Polystyrene (Foam Cups, Packing Peanuts)
• Polycarbonate (aka Lexan, Bulletproof Glass)
• Polyamide (Nylon)

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What Is Used to Make Plastic Stuff?

• Injection Molding
• Injection Blow Molding
• Injection Stretch Blow Molding
• Extrusion Molding
• Extrusion Blow Molding
• Rotational Molding

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Why Use Plastic?

• Looks Good
• Durable
• Flexible
• Light Weight
• Easy to shape and color
• Cheap

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The Plastic Age

• Stuff made out of plastic is everywhere
• Cell phones, computer parts, car parts, tables,
  chairs, etc.
• New uses for plastic being discovered everyday
• What used to be glass is now made in plastic
• What used to be metal is now made in plastic
• What used to be wood is now made in plastic
• Plastic has revolutionized the world

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References

• http//web.umr.edu/wlf/CHEM381/chap11.html
• http//www.calibre.co.nz/plastics.htm
• http//www.packagingtoday.com/intronaturalpolymers
  .htm
• http//www.packagingtoday.com/introplasticexplosio
  n.htm
• http//www.teachingplastics.org/hands_on_plastics/
  intro_to_plastics/teachers.html