What gives Kevlar its bulletproof strength?

the hydrogen bonds between polymer chains

aromatic stacking

the carbonyl groups which are placed between oxygen atoms

nitrogen – hydrogen bonds

aromatic stacking

Explanation:

Kevlar derives its bulletproof strength from aromatic stacking of its molecules. Although like most compounds having hydrogen bonds, it is quite strong but its unique property which makes it useful due to its strength is as a result of aromatic stacking.

It is an aromatic polymer made up of several units  of monomers of terephthalic acid and 1,4-diaminobenzene.

The stack maximizes the hydrogen bonds and the amide linkages which therefore furnishes its unique strength.