A fiber of Kevlar is actually a bundle of polymer chains.
What holds the polymer chains together?

   
 

Imagine a box of uncooked spaghetti. As you look at it, there is nothing holding all of the noodles together, and if you turned the box upside down, all of the spaghetti would fall out.


Even though the polymer chains of Kevlar are long individual chains like spagehetti noodles, they are different because the chains behave as if they are attached together. But how are they attached?

  • Are the polymer chains glued together?
  • Are they similar to jigsaw puzzle pieces and held together by their shape?
  • Are they magnetically attracted to each other?
The idea of attraction between magnets is an analogy that helps in understanding the attractive forces between polymer chains. The individual polymer chains are actually held together by electrostatic forces between molecules known as hydrogen bonds.

Click here to learn more about hydrogen bonds:

                                     

When it comes to hydrogen bonds, Kevlar and water have something in common. In both compounds, the oxygen atoms have a high density of electrons around the nucleus. Since electrons are negatively charged, this gives the oxygen atoms a slight negative charge. On the other hand, hydrogen atoms have a much lower density of electrons around the nucleus, giving the hydrogen atoms a partial positive charge. Like the north and south poles of magnets, the positive hydrogen and negative oxygen of different molecules attract each other, forming hydrogen bonds.

Hydrogen bonding in water.

Hydrogen bonding in Kevlar.

CLUE #4: The individual polymer strands of Kevlar are held together by hydrogen bonds that form between the polar amide groups on adjacent chains.

Kevlar Introduction

Clue #1

Clue #2

Clue #3

Clue #5

Putting the Pieces Together

   
 

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