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Chapter 10 Polymers: Giants Among Molecules. Macromolecules. Compared to other molecules, they are enormous Molar mass: 10,000–1,000,000+ g/mol Not visible to naked eye Polymers: made from smaller pieces Monomer: small chemical building block

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macromolecules
Macromolecules
  • Compared to other molecules, they are enormous
    • Molar mass: 10,000–1,000,000+ g/mol
    • Not visible to naked eye
  • Polymers: made from smaller pieces
    • Monomer: small chemical building block
  • Polymerization: process in which monomers are converted to polymers

Chapter 10

natural polymers
Natural Polymers
  • Found extensively in nature
    • Life could not exist without polymers
    • Come in various shapes and sizes
  • Made of sugars, amino acids, nucleic acids
  • Examples: wool, silk, cotton, wood, paper

Chapter 10

celluloid
Celluloid
  • React cellulose with nitric acid
  • Used for first films and billiard balls
  • Highly flammable
    • Used in smokeless gunpowder
  • No longer in use

Chapter 10

synthetic polymers
Synthetic Polymers
  • Made from monomer synthesized from fossil fuels
  • First manufactured shortly before World War II
  • Synthesized using addition reactions
    • Add monomer to end of polymer chain
    • Build very large polymers

Chapter 10

polyethylene
Polyethylene
  • Cheapest and simplest synthetic polymer
    • Made from CH2=CH2
    • Invented shortly before World War II
  • Has two forms
    • High-density polyethylene (HDPE)
    • Low-density polyethylene (LDPE)

Chapter 10

thermoplastic and thermosetting polymers
Thermoplastic and Thermosetting Polymers
  • Thermoplastic polymer: softened by heat or pressure and reshaped
    • Polyethylene
  • Thermosetting: harden permanently when formed
    • Once formed, cannot be reshaped

Chapter 10

polypropylene
Polypropylene
  • Change a –H to –CH3
  • Harder and has higher melting point than polyethylene

Chapter 10

polystyrene
Polystyrene
  • Change a –H to benzene ring
  • Widely used
    • Disposable cups
    • Insulation

Chapter 10

vinyl polymers
Vinyl Polymers
  • Change a –H to –Cl
  • Tough thermoplastic
    • Polyvinyl chloride (PVC)

Chapter 10

teflon
Teflon
  • Change all –H to –F
    • C–F very strong. Resists heat and chemicals
    • Makes very unreactive polymer

Chapter 10

other polymers
Other Polymers

Chapter 10

rubber
Rubber
  • Pre–World War II
    • Came from natural sources in S.E. Asia
    • Japan cut off supply during World War II
  • Made of isoprene
  • Chemists learned to make it during World War II

Chapter 10

vulcanization
Vulcanization
  • Link individual polymer strands with S atoms
  • Makes rubber stronger
    • Can be used on natural or synthetic rubber
  • Elastomers: materials that stretch and snap back
    • Key property of rubber

Chapter 10

synthetic rubber
Synthetic Rubber
  • Use butadiene
    • CH2=CH-CH=CH2
  • Polychloroprene: substitute –Cl for a –H
  • Change the properties for other uses
    • Tend to be resistant to chemicals

Chapter 10

copolymerization
Copolymerization
  • Add two or more different monomers
  • Uses addition reaction
  • Allows for modification of polymer’s properties
  • Styrene–butadiene rubber (SBR)
    • 75% butadiene/25% styrene mix
    • Used mainly for tires

Chapter 10

condensation polymers
Condensation Polymers
  • Part of the monomer will not be incorporated into the final material
    • Typically a small molecule like water
  • Formula of the repeating unit not same as monomer
  • Used to produce nylon and polyesters

Chapter 10

composite materials
Composite Materials
  • Use high-strength polymers
    • Could include glass, graphite, or ceramics
  • Hold everything together with polymers
    • Typically thermosetting, condensation polymer
  • Result is a very strong, lightweight material
    • Used in cars, sports gear, boats

Chapter 10

silicone polymers
Silicone Polymers
  • Based on alternating Si and O atoms
  • Heat stable and resistant to most chemicals
  • Properties depend on length of polymer
  • Many uses
    • Shoe polish, coatings on raincoats, Silly Putty

Chapter 10

properties of polymers
Properties of Polymers
  • Crystalline: polymers line up
    • High tensile strength
    • Make good synthetic fibers
  • Amorphous: polymers randomly oriented
    • Make good elastomers
  • Some material has both types of polymers mixed together
    • Flexibility and rigidity

Chapter 10

slide24
Glass transition temperature, Tg
    • Above Tg, polymer is rubbery and tough
    • Below Tg, polymer hard, stiff, and brittle
  • Determine where polymer will be used
  • What type of Tg do you want your plastic coffee cup to be?

Chapter 10

fiber forming properties
Fiber-Forming Properties
  • Majority of fabrics made of synthetic polymers
  • Tend to last longer, easier to care for
    • Nylon vs. silk
  • Also may make mixtures
    • Cotton/polyester blends

Chapter 10

disposal of plastics
Disposal of Plastics
  • Do not degrade readily
    • Designed to be durable
    • Last a long time
  • Make up 8% by mass of landfills
    • But make up 21% by volume
    • Tend to fill up landfills
  • Incinerate plastics
    • Produce lots of heat when burned
    • May give off unwanted by-products
  • Degradable plastics
    • Photodegradable: need light to break down
    • Biodegradable: break down in presence of light
    • Do not want to degrade too soon

Chapter 10

recycling
Recycling
  • Collect, sort, chop, melt, and then remold plastic
  • Requires strong community cooperation

Chapter 10

plasticizers
Plasticizers
  • Make plastic more flexible and less brittle
    • Lower Tg
    • Tend to be lost as plastic ages
  • Most common plasticizers today based on phthalic acid

Chapter 10

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