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What is Kevlar?

Kevlar® is an object most people might be familiar with, but they never really know what it means. Digging through its colorful history and intricate synthesis, the material has a fascinating story to tell.

Kevlar® is a common term for the polymer poly-paraphenylene terephthalamide, a synthetic chemical made by combining two kinds of polymers in an acid. It was first used as lining for bicycle tires, but as time passed, its function has branched out to other industries.


The History of Kevlar

Kevlar® was developed by an American chemist named Stephanie Kwolek back in 1965. At that time, the world was anticipating a shortage in gasoline. Companies were looking for lighter materials to improve fuel economy.


DuPont gathered a team of researchers and gave them the important task of looking for a lightweight but strong replacement of steel in tires. Kwolek was part of that team.


The discovery was more of an accident. Instead of throwing a liquid-crystalline mixture of p-phenylene-terephthalate and polybenzamide in the bin, Kwolek convinced a colleague to check if they can spin it into long and thin fibers without breaking.


Surprisingly, the experiment was a success. By 1971, the modern version Kevlar® was introduced to the masses.



How Kevlar is Made

The process of making Kevlar® has undergone massive changes over the years.


The modern version is synthesized by combining 1,4-phenylene-diamine and terephthaloyl chloride with N-methyl-pyrrolidone in concentrated sulfuric acid. This produces a liquid-crystalline product, which is spun into ropes of fabric sheets.


Kevlar Properties

Like carbon fiber, Kevlar® also has a high strength to weight ratio. It is 5 times stronger and lighter than steel.


Strength increases as conditions reach cryogenic temperatures (less than 0 degrees Celsius). However, strength decreases by 10% if the temperatures are higher than 160⁰C.


Applications for Kevlar

Kevlar® has been used in the following:

  • Personal protection. Combat armors, jackets and gloves are made out of Kevlar to protect the wearer from cuts.
  • Bicycle tires. It is found in the inner lining to prevent punctures.
  • Drumheads. Drum sets with Kevlar® have higher sound quality.
  • Boat hulls. Kevlar® is a very popular choice among boat hulls, because it can withstand a huge amount of force and impact. A lightweight boat is also faster, therefore it requires less rowing effort to move.
  • Fighter Jets. The Eurofighter jets are well-known for its speed and agility, thanks to its Kevlar® panels and wings.

Disadvantages of Kevlar

On the flip side, Kevlar® costs an arm and a leg. The presence of sulfuric acid in the mixture allows the polymer to stay in solution form during synthesis and spinning. Therefore, eliminating it in the recipe is close to impossible.


Additionally, it cannot be used during daytime without installing protective equipment. The sun’s UV rays degrade the structure, immediately reducing its strength.


The Bottom Line

Despite its disadvantages, we cannot deny how Kevlar® has made our lives better. Our transportation, sports and tactical gear will never be what it is today without this polymer. Thank you, Kwolek and DuPont.

September 25, 2014 by Ralph Rodriguez
Tags: kevlar
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