ch4-S09 - Chapter 4: Structure of Polymers structure...

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MY2100 – Ch 4, Slide 1 Chapter 4: Structure of Polymers structure processing properties Performance ISSUES TO ADDRESS. .. What are the general structural and chemical characteristics of polymer molecules? How is the crystalline state in polymers different from that in metals and ceramics ? What are some of the common polymeric materials, and how do they differ chemically?
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MY2100 – Ch 4, Slide 2 How to build a polymer - initiation The best way to understand the structure of polymers is to look at how they are formed - this is a process called polymerization. Polymerization: Formation of a polymer molecule using a controlled chemical reaction between a “building block” molecule and an initiator or catalyst molecule. Basic building block monomer C 2 H 4 (ethylene gas) R = “Radical: electron- deficient compound ( ) that breaks a C double covalent bond (C=C) + R R H H C = C H H H H C C H H
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MY2100 – Ch 4, Slide 3 How to build a polymer - propagation C C H H H H monomer (ethylene) R + free radical R C C H H H H initiation R C C H H H H C C H H H H + R C C H H H H C C H H H H propagation dimer The polymer chain then forms by the addition of more monomer units to the initial molecule - the active site is transferred to each successive end monomer as it is linked to the chain. Eventually, two of these chains are linked together and the overall polymer molecule stops growing.
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MY2100 – Ch 4, Slide 4 Polyethylene Milk jugs, structural plastics The repeated addition of other C 2 H 4 mer units produces the polymer structure (polyethylene - PE) (a) Idealized drawing (b) More realistic drawing This type of polymerization is called addition or chain polymerization and results in chain (also called linear) polymers.
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MY2100 – Ch 4, Slide 5 Other mer units are possible Polyethylene is typical of a large number of polymers. They have
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This note was uploaded on 03/16/2011 for the course MY 2100 taught by Professor Staff during the Spring '08 term at Michigan Technological University.

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ch4-S09 - Chapter 4: Structure of Polymers structure...

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