Polymers Polymers From the Greek poly meaning many

Polymers From the Greek: poly meaning many; mer meaning unit. Monomer is the basic

Characteristics of Polymers Based on response to heat. Thermoplastics: when heated repeated will soften

1. 2. 3. 4. 5. Polymers can be resistant to chemicals Polymers can be

Addition Polymerization 3 Basic Steps: Initiation: double bonds break and begin to bond together.

Types of Addition Polymers Polyethylene: monomer is ethylene. Most widely used. LDPE (4) is

Polyvinylchloride (3): monomer is vinyl chloride. Can be made three ways: head-to-tail, headto-head, or

Condensation Polymers Polymer in which two molecules combine by spitting out a small molecule

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Polymers

Polymers From the Greek: poly meaning many; mer meaning unit. Monomer is the basic unit. Can be natural or manmade. First synthetic polymer is Bakelite discovered in 1907. Most common polymers have a carbon backbone with hydrogen attached. Monomers are chemically joined together in one of two ways: addition or condensation.

Characteristics of Polymers Based on response to heat. Thermoplastics: when heated repeated will soften and flow. When cooled, it hardens again. It is a reversible process. Ex. Polystyrene Thermosets: when heated forms a set of interlocking bonds. When reheated it cannot soften and reformed. Ex. Bakelite.

1. 2. 3. 4. 5. Polymers can be resistant to chemicals Polymers can be both thermal and electrical insulators. Polymers are very light in mass with varying degrees of strength. Polymers can be processed in various ways to produce thin fibers or very intricate parts. Can be distinguished by melting point, density, burning properties, or solubility.

Addition Polymerization 3 Basic Steps: Initiation: double bonds break and begin to bond together. l Propagation: continued addition of monomers into chains. l Termination: need to be quenched. l In addition polymers, all reactants end up in the polymer. l

Types of Addition Polymers Polyethylene: monomer is ethylene. Most widely used. LDPE (4) is branched. It is soft, flexible solid that is used in films and coatings. HDPE (2) is a long chain. Neighboring chains line up parallel to each other. This is used in bottles, toys, semirigid objects.

Polyvinylchloride (3): monomer is vinyl chloride. Can be made three ways: head-to-tail, headto-head, or random. Usually head-to-tail. Polypropylene (5): monomer is propene. Used in indoor-outdoor carpets, bottles. Polystyrene (6): monomer is styrene. Can be a foam (strofoam) or rigid(eating utensils)

Condensation Polymers Polymer in which two molecules combine by spitting out a small molecule like water. (H+ - OH-) Requires two kinds of functional groups on two different molecules. Alcohol + acid ester PET polyethylene terephthlate (polyester) reaction between terephthalic acid and ethylene glycol.

Kevlar July 2002