Kevlar (poly-phenyleneterephtalamide)

Nathan Yip & David Wieand


Structural Formula: C14H10N2O2

(14 carbon atoms, 2 nitrogen atoms, 2 oxygen atoms and 10 hydrogen atoms)
Kevlar is a fairly large polymer with many hydrogen bonds which are extremely strong.


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Diagram 1. The monomer

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Diagram 2. Kevlar monomers linked together

Kevlar is a synthetic polymer because it’s actually made and produced. You won’t be able to find Kevlar in nature. Kevlar is also non-biodegradable, meaning that it won’t be able to degrade on its own. It is recyclable and a good example would be a belt made from a recycled Kevlar bike tire. It is non-thermoplastic simply because it’s not a plastic, it is an elastomer because of its stretchy and elastic properties. It is also a fiber. Cross-linkage occurs in the molecular makeup of Kevlar and the more cross-linkage that occurs, the stronger the polymer. The molar mass for Kevlar is 238.0 grams and it's melting point is 427 C - 482*C.

Chemical Properties:

Physical Properties:

Structurally Rugged
Specific heat 1400 J/kg K
Low Electrical Conductivity
Density 1.44 g/cm3
High Chemical Resistance
High heat resistance
Low Thermal Shrinking
Extreme strength
Excellent Dimensional Stability

Flame Resistant, Self-Extinguishing

Concentrated acids can dissolve Kevlar

Dilute acids are slower at dissolving Kevlar

Good resistance towards alcohols, alkalis,
greases and oils, halogens, and ketones



There are three types of Kevlar: regular Kevlar, Kevlar 29, and Kevlar 49. Kevlar 29 is typically used to produce industrial type materials such as cables and body armor. Kevlar 49 is the strongest type of Kevlar in general; it’s used to reinforce plastic on boat hulls, airplanes, and bikes. Since Kevlar is weak when it comes in contact with ultraviolet light from the sun, it needs protection from use outdoors.
The molecular structure of Kevlar has repeating groups between the links called benzene rings. They are hexagonal rings each made of six carbons bonded to a hydrogen atom.

Uses of Kevlar:

  • Body armor (bulletproof vests, masks)
  • “Puncture proof” car tires
  • Kevlar sails on sailboats (wont tear, not easily punctured, lightweight)
  • Canoes and kayaks made of mostly Kevlar (light, high impact resistance)
  • Trampolines
  • Ice hockey sticks
  • Flame resistant suits (firefights)
  • Ropes that secure airbags
  • Landing gear of planes, space equipment
  • Shrapnel-resistant shielding in jet aircraft engines to protect passengers if there was an explosion
  • Gloves that help protect against cuts and slashes
  • Skis (lightweight, strong)
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Firefighters with Kevlar suits

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Police in a Kevlar vest

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Police dog in a Kevlar vest


As you can see, Kevlar is used frequently for protection because of it's ability to withstand bullets and heat to a certain extent.

References
:

Caswell, Adam. Police, EMT, and Firefighter Applications. 18 May 2008 <http://ffden2.phys.uaf.edu/212_fall2003.web.dir/adam_caswell/page2.htm>.

Kevlar. Wikipedia. 18 May 2008 <http://en.wikipedia.org/wiki/Kevlar>.

"Properties." Kevlar. Virtual Science Fair. 18 May 2008 [[http://www.virtualsciencefair.org/2004/clar4c0/public_html/en/properties.html%3C/span%3E.|http://www.virtualsciencefair.org/2004/clar4c0/public_html/en/properties.html.]]

Davies, Simon. "Kevlar: Bullet-Proof Polymer." Suite 101. 18 May 2008 <[[http://everydaychemistry.suite101.com/article.cfm/kevlar_bulletproof_polymer%3E.%3C/span%3E%3C/span%3E%3C/span|http://everydaychemistry.suite101.com/article.cfm/kevlar_bulletproof_polymer>.
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