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Chapter 2- Polymer Chemistry
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2.1 Introducting Polymers
Monomer: the smallest repeating unit of a polymer (propene in polypropylene). Polymer: a long chain molecule made up of many small identical units (monomers). Polymerization: process of linking monomer units into a polymer. Can be accomplished by addition or condensation reactions. Homopolymer: a polymer made of only a single type of monomer Copolymere: are polymers made of two or more types fo monomers
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Natural Polymers Nature produces a variety of polymers.
They are built by an organism. Examples are : Silk, natural rubber, starch, chitin, proteins,
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Synthetic Polymers Usually produced from plant material or petrochemicals Examples include: Nylon, Kevlar, non-stick coating (fluoropolymers), polyester, tires
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Synthetic Polymers involve 3 stages in the polymerization process
1 Initiation- removes a part of the monomer to make it want to bond with another monomer 2 Propagation- the process keeps going 3 Termination- a chemical is used that causes the monomers to stop joining together
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2.2 Synthetic Addition Polymers
Addition polymerization: a reaction in which unsaturated monomers combine with each other to form a polymer. A reaction where monomers with double bonds are joined together through multiple addition reactions to form a polymer
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Properties of a polymer are determined by the properties of its monomers, which may include functional groups such as alkyl groups, halides, aromatic groups and alcohols.
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Examples of Addition Polymers
Teflon, polypropylene, polyester, polyethylene (pop bottles, grocery bags), polystyrene (packing material), Plexiglas, polyvinyl chloride (vinyl), natural rubber, etc
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Example Polyvinyl Chloride
Example Polystyrene
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Plastics A polymer that retains its shape after being heated under pressure and subsequently cooled. Plastics tend to be: Unreactive Flexible in Shape Vary in hardness
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Polymer Cross-Linking
Cross-linking arises when functional groups on a chain can interact. The softness of a plastic is related to the amount of cross-linking. The greater the level of cross-linking, the more heat resistant a polymer becomes
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Work Pg. 83 # 1-3 Pg. 87 # 1-3 Pg. 93 # 1-4
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2.4 Synthetic Condensation Polymer
Condensation polymerization: a reaction in which two different monomers react at the functional group to form a polymer. Generally a reaction where two monomers are joined to form a unit called a dimer. A dimer generally consists of an ester or amide linkage. If a chemical is bi-functional (having two different functional groups) it can form a condensation polymer with itself.
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Question what types of chemicals do we need to use to get the dimers?
Polyamide A dicarboxylic acid and diamines Polyester A diacarboxylic acid and dialcohols
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Condensation Reaction
With two different molecules: With one type of molecule:
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Polyester
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The Formation of Dacron
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Formation of Nylon 6,6
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Work Pg. 98 # 1 Pg. 99 # 1-6
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