Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Design of Polymers for Industrial Applications: Kevlar and Teflon

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Teflon and Kevlar Advances in polymer technology and discovery have been influencing lives for the past 50 years The inventions of kevlar and teflon have had an impact on everyday life… Can you name any places you have seen these materials?

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Journal Activity Write in your journal the applications you have seen Kevlar and Teflon… Where have you seen these materials? What purpose do they have in the particular applications?

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Look at These ympics/suitup.jsphttp:// ympics/suitup.jsp ympics/skis.jsphttp:// ympics/skis.jsp ympics/ ympics/

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. What is Kevlar? Synthetic polymer fiber Developed by DuPont in 1965 Known for high strength and lightweight properties

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Structure of Kevlar Polyamides: polymers where repeating units are amides –Amide group: Kevlar structure: Other polyamides: nylon ─ C ─ N ─ H O H O ─ N ─ C ─ H O

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Unique Properties of Kevlar: Stength Tensile Strength of 3,620 Mpa!! Density of 1.44 For comparison: Other materials Other FibersDensity (lb/in 3 ) Tensile Strength Decomposition Temperature (  C) KEVLAR0.052~500 psi Glass fibers psi700+ Steel Wire Polyester

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Unique Properties of Kevlar: Heat Resistance KEVLAR does not melt! Decomposes at 427  C and higher Elevated temperatures can reduce tensile strength, but only by ~10% Flame-resistant –Used in personal protective equipment

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. How does Kevlar get its strength? Intermolecular (chain) bonding! Hydrogen bonds between NH groups and O in carbonyl (red) Aromatic stacking interactions (green)

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Applications of Kevlar Bicycle tires Racing tires Ropes and Cables – used in suspension bridges Body armor – helmets and vests Protective Equipment for firefighters

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Specialty Polymers: Teflon Can you name some applications in your home where teflon is used?

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Specialty Polymers: Teflon Can you name some applications in your home where teflon is used? –Cooking utensils (nonstick cookware), fabric protectors (carpet, furniture), seals, eyeglass lenses, wiper blades

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Structure of Teflon Teflon Structure: polytetrafluoroethylene (PTFE) Called a flouropolymer – only carbon and flourine in molecule

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Properties of Teflon Hydrophobic: does not like water Nonreactive Nonstick High temperature resistance (up to 300  C) Good dielectric properties: –Suitable for use as an insulator Low coefficient of friction

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. The Carbon-Fluorine Bond High electronegativity of F Bond is very polar Partial charges on atoms results in a high bond strength and shorter bond length  +  - C ─ F

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Supplementary Slides

Copyright © 2011, Carnegie Mellon University. All Rights Reserved. Websites and Resources ex.htmlhttp://www2.dupont.com/Kevlar/en_US/ind ex.html –Kevlar sets/downloads/KEVLAR_Technical_Guid e.pdfhttp://www2.dupont.com/Kevlar/en_US/as sets/downloads/KEVLAR_Technical_Guid e.pdf