MECH
Notes-11 (2 slides per page).pdf

Notes-11 (2 slides per page).pdf - Polymers INCLUDES...

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Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 1 Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 1 INCLUDES: Plastics & Elastomers Plastics & Elastomers are made from polymeric materials COMMERCIAL Polymers: used in large quantities for their lightweight, corrosion-resistance, and good formability. (usually low strength and stiffness. ENGINEERING Polymers: improved strength and better elevated temp. properties. Polymers Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 2 Originally natural polymers were used – Wood – Rubber – Cotton – Wool – Leather – Silk Oldest known uses Rubber balls used by Incas Pitch (a natural polymer) used to seal boats Ancient Polymer History Polymers in our body?
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Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 2 Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 3 Most polymers are hydrocarbons – i.e. made up of H and C Saturated hydrocarbons Each carbon bonded to four other atoms C C H H H H H H C n H 2n+2 Polymer Composition Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 4 Polymer Composition
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Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 3 Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 5 Double & triple bonds relatively reactive – can form new bonds Double bond – ethylene or ethene - C n H 2n Each C has 4-bonds, but only 3 atoms bound to each C Triple bond – acetylene or ethyne - C n H 2n-2 Each C has 4-bonds, but only 2 atoms bound to each C C C H H H H C C H H Unsaturated Hydrocarbons The basic building block of polymers is the hydrocarbon molecule. Each Carbon atom wants to form 4 covalent bonds. o If double or triple bonds form – unsaturated molecules. o The double and triple bonds allow the molecule to join to something else under the right conditions. Other groups can be attached to the carbon atoms apart from -H, So basically the various (multitudinous) polymers are made by taking varying proportions of hydrocarbons and end groups and assembling them together. Mers ( Monomers ) are the basic building unit. These are combined to form the polymer. e.g. Polyethylene - very common polymer: bags, containers, films etc. Hydrocarbon Molecules
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Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 4 Dr. Rezabeigi-MECH 221-Lecture 11 (adapted from Callister) 7 Two compounds with same chemical formula can have quite different structures o Ex: C 8 H 18 a) n-octane b) 2-methyl-4-ethyl pentane (isooctane) H 3 C CH CH 3 CH 2 CH CH 2 CH 3 CH 3 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 2 CH 3 ( ) 6 Isomerism Concept similar to …. In ceramics?
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  • Fall '09
  • Polymer, Dr. Rezabeigi-MECH 221-Lecture

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