4.Polymer%20structure - MSE 280: Engineering Materials...

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1 MSE 280: Engineering Materials Reading: Callister Ch. 4 & 14.11 Polymer Structures • Classification. • Monomers and chemical functional groups. • Nomenclature. • Polymerization methods. • Molecular weight & degree of polymerization. MSE280 © 2007-2009 Moonsub Shim, University of Illinois 1 • Molecular structures. • Copolymers. • Crystallinity. Polymers -Very large molecules ( macromolecules ) that are composed of smaller repeating units ( monomers ). -Examp les: - Textile fibers: polyester, nylon… - IC packaging materials. - Resists for photolithography/microfabrication. A + A A-A A-A-A ….. A MSE280 © 2007-2009 Moonsub Shim, University of Illinois 2 - Plastic bottles (polyethylene plastics). - Adhesives and epoxy. - High-strength/light-weight fibers: polyamides, polyurethanes, Kevlar… - Biopolymers: DNA, proteins, cellulose…
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2 Classification Thermoplastics : polymers that flow more easily when squeezed, pushed, stretched, etc. by a load (usually at elevated T). – Can be reheated to change shape. Thermosets : polymers that flow and can be molded initially but their shape becomes set upon curing. – Reheating will result in irreversible change or decomposition. • Other ways to classify polymers. B h i l f ti lit ( l l t l id MSE280 © 2007-2009 Moonsub Shim, University of Illinois 3 – By chemical functionality (e.g. polyacrylates, polyamides, polyethers, polyeurethanes…). – Vinyl vs. non-vinyl polymers. – By polymerization methods (radical, anionic, cationic…). –E t c… Chemical functional groups CC H H H H Ethylene (ethene) H H C H H H H Propylene (propene) = 1-butene 2-butene MSE280 © 2007-2009 Moonsub Shim, University of Illinois 4 Saturated hydrocarbons trans cis Acetylene (ethyne) H H Unsaturated hydrocarbons
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3 Chemical functional groups MSE280 © 2007-2009 Moonsub Shim, University of Illinois 5 Some common polymers CC C H H H Polyacrylonitrile (PAN) teflon MSE280 © 2007-2009 Moonsub Shim, University of Illinois 6 N Note: many of these polymers have backbone. H H H X n H H X H Vinyl polymers (one or more H’s of ethylene can be substituted)
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4 Nomenclature Monomer-based naming: poly poly________ e.g. ethylene -> polyethylene if monomer name contains more than one word: poly( ) Monomer name goes here MSE280 © 2007-2009 Moonsub Shim, University of Illinois 7 _____ ____ e.g. acrylic acid -> poly(acrylic acid) Monomer name in parentheses polymethylene Molecular Weight Not only are there different structures (molecular arrangements) but there can also be a distribution of molecular weights (i.e. number of monomers per polymer molecule). 20 mers 16 mers MSE280 © 2007-2009 Moonsub Shim, University of Illinois 8 10 mers Average molecular weight = monomer monomer M M 3 . 15 3 10 16 20 = + + This is what is called number average molecular weight.
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5 Molecular Weight Number average molecular weight: j j M N j o j N m = j j j n N M N j = number of polymer chains with length j M j = jm o = mass of polymer chain with length j m o = monomer molecular weight = j j j N MSE280 © 2007-2009 Moonsub Shim, University of Illinois 9 = j j j M N Note: Total weight = j j N Total # of polymer chains Molecular Weight Weight average molecular weight:
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This note was uploaded on 03/15/2010 for the course MSE 280 taught by Professor Johnson during the Fall '08 term at University of Illinois, Urbana Champaign.

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4.Polymer%20structure - MSE 280: Engineering Materials...

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