ENME382 S2010 0201 ch04_1

ENME382 S2010 0201 ch04_1 - CHAPTER 4: POLYMER STRUCTURES...

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ISSUES TO ADDRESS. .. What are the general structural and chemical characteristics of polymer molecules? What are some of the common polymeric CHAPTER 4: POLYMER STRUCTURES Chapter 4 - ENME 382 Spring 2010 Section 0201 1 materials, and how do they differ chemically? How is the crystalline state in polymers different from that in metals and ceramics ?
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What is a Polymer? Poly mer many repeat unit repeat unit repeat unit repeat unit Chapter 4 - ENME 382 Spring 2010 Section 0201 2 Adapted from Fig. 4.2, C C C C C C H H H H H H H H H H H H Polyethylene (PE) Cl Cl Cl C C C C C C H H H H H H H H H Poly(vinyl chloride) (PVC) H H H H H H Polypropylene (PP) C C C C C C CH 3 H H CH 3 CH 3 H
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Polymer Composition Most polymers are hydrocarbons – i.e., made up of H and C • Saturated hydrocarbons – Each carbon singly bonded to four other atoms – Example: Chapter 4 - ENME 382 Spring 2010 Section 0201 3 • Ethane, C 2 H 6 C C H H H H H H
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Chapter 4 - ENME 382 Spring 2010 Section 0201 4
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Unsaturated Hydrocarbons can form new bonds – Double bond found in ethylene or ethene - C 2 H 4 C C H H Chapter 4 - ENME 382 Spring 2010 Section 0201 5 – Triple bond found in acetylene or ethyne - C 2 H 2 H H C C H H
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Isomerism • Isomerism – two compounds with same chemical formula can have quite different structures for example: C 8 H 18 • normal-octane Chapter 4 - ENME 382 Spring 2010 Section 0201 6 • 2,4-dimethylhexane C C C C C C C C H H H H H H H H H H H H H H H H H H H 3 C CH 2 CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 = H 3 C CH CH 3 CH 2 CH CH 2 CH 3 CH 3 H 3 C CH 2 CH 3 ( ) 6
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Polymerization and Polymer Chemistry • Free radical polymerization C C H H H H monomer (ethylene) R + free radical R C C H H H H initiation Chapter 4 - ENME 382 Spring 2010 Section 0201 7 • Initiator : example - benzoyl peroxide C H H O O C H H C H H O 2 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 R = 2
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Chemistry and Structure of Polyethylene Adapted from Fig. 4.1, Callister & Rethwisch 3e. Chapter 4 - ENME 382 Spring 2010 Section 0201 8 Note: polyethylene is a long-chain hydrocarbon - paraffin wax for candles is short polyethylene
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Bulk or Commodity Polymers Chapter 4 - ENME 382 Spring 2010 Section 0201 9
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Bulk or Commodity Polymers (cont) Chapter 4 - ENME 382 Spring 2010 Section 0201 10
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Bulk or Commodity Polymers (cont) Chapter 4 - ENME 382 Spring 2010 Section 0201 11
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MOLECULAR WEIGHT Molecular weight , M : Mass of a mole of chains. Low
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This note was uploaded on 01/24/2011 for the course ENME enme382 taught by Professor Bruck during the Spring '10 term at Maryland.

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ENME382 S2010 0201 ch04_1 - CHAPTER 4: POLYMER STRUCTURES...

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