POLYMERS

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POLYMERS
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Polymers

• Polymers are macromolecules that are formed by
  the linking of repeating units through covalent
  bonds in the main backbone
• examples are plastics
• Polymer- large molecule formed by the covalent
  bonding of smaller molecules called monomers

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Properties of Polymers

• Polymers are stretchable, malleable, and
  flexible.
• When cross-links are formed in a polymer, its
  chains of molecules are connected in several
  places, producing a stronger and more elastic
  polymer.
• The elasticity of some (thermoplastic) polymers
  is affected by temperature.

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Polymer Facts

• Some polymers occur naturally, as in the juice of
  rubber or aloe plants, and some are manmade.
• Examples are plastic bottles, Styrofoam, latex
  paints, and chewing gum.

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Polymers made from Monomers
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Polymer Structure

• cross-linking
• A process in which bonds are formed joining
  adjacent molecules. At low density, these bonds
  add to the elasticity of the polymer and at
  higher densities, eventually produce rigidity in
  the polymers.

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Polymer Structures
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Addition Polymers

• An addition polymer forms when unsaturated
  monomers react to form a polymer
• ethene will form polyethylene
• polyethylene is easy to clean, chemically
  resistant- milk bottles, plastic wrap,
  refrigerator dishes

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High Density Polyethylene
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Addition Polymer Process
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Addition Polymers

• Polypropylene is a stiffer polymer, used in
  utensils and containers
• Polystyrene is formed from styrene
  (phenylethene), and is a poor heat conductor
  (styrofoam Dow Chemical)
• molded coffee cups and picnic coolers, insulates
  homes
• Polyvinyl chloride (PVC) used for pipes in
  plumbing

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Addition Polymers

• Polytetrafluoroethene (PTFE, or teflon DuPont)
  is very resistant to heat and chemical corrosion
• found on nonstick cookware coating on bearings
  and bushings used in chemical reactors

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Condensation Polymers

• Condensation polymers are formed by the
  head-to-tail joining of monomer units
• usually accompanied by the loss of water from the
  reacting monomers, and forming water as a product

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Condensation Polymer Process
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Condensation Polymers

• Ex polyethylene terephthalate (PET)
• Dacron ( DuPont), Fortrel ( Wellman),
  Polyesters permanent press clothing, tire cords
• Sheets of polyester called Mylar ( DuPont), used
  as magnetic tape in tape recorders and computers,
  as well as balloons
• Nylon carpet, fishing line, hosiery

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Condensation Polymers

• Examples
• aromatic rings form Nomex ( DuPont), which is a
  poor electrical conductor makes parts for
  electrical fixtures flame resistant clothing for
  race car drivers flame resistant building
  materials
• Kevlar ( DuPont) strong and flame resistant

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Timeline of Plastics
1862 First man-made plastic 1866 Celluloid
makes its debut 1891 Rayon is discovered 1907
Bakelite is invented 1913 Cellophane causes
the plastics craze
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Timeline of Plastics
1926 PVC is invented 1933 Polyethylene is
discovered 1933 Saran makes its debut 1938
Teflon is discovered 1939 Nylon stockings hit
market 1957 Here comes velcro