We inhabit a universe that contains billions of billions of organic compounds, each one having the capability to serve humanity in a unique way. Some of these organic compounds are even referred to as life saving. These compounds have a special place in modern society. Among them are compounds that allow for better medical techniques, safer laboratory conditions for scientists, inflatable life rafts for one-time passengers on an ill-fated ship, and something that covers almost every man and woman put in harm’s way in the line of duty.
This compound, known as Kevlar (a trademark of DuPont, Incorporated) has the power to stop a bullet-something few other wearable materials can compare to. The specially designed and synthetically produced fabric has applications that range from bulletproof vests to automobile tires to circuit board reinforcement.
The monomer found in Kevlar’s chemical formula is C14N2O2H10 (please see figure 1).
By extruding the molten polymer solution through miniscule holes and micro-weaving the resulting threads, Kevlar can possess a certain degree of crystallinity. This factor contributes to its strength and rigidity.
As well, the fact that Kevlar is a polyaromatic amide, meaning it contains amino groups as well as aromatic groups means it has a much higher breaking strength than other compounds such as Rayon and Nomex. Hydrogen bonding accounts for the individual strands holding together (please see figure 2). The regularity and symmetry that this hydrogen bonding causes it what gives the compound its crystalline-like qualities, and is what accounts for its strength.
These hydrogen bonds form between the polar amide groups on adjacent chains.
Any peace officer, in any line of duty, deployed anywhere in the world, has a friend whose life has been saved by Kevlar, or, even more dramatically, has had their own life spared because of this polymer. Because of its low-density honeycombed core, Kevlar is extremely puncture proof. This means that while a vest made out of this compound will stop a bullet, a pair of gloves made out of it will prevent the user from being pricked by a needle of dubious origins.
Kevlar is included in the design of most of the protective gear employed by the 1st world’s armies. All troop helmets have an inner lining of the material, followed by an outer lining of steel. The US government equips its Secret Service with cars that have Kevlar in the door panel. This shows that where steel and aluminum may fail, the manufacturers expect Kevlar to hold fast.
In the aftermath of a war, civilians are often left to clean up unwanted leftovers of the conflict-such as antipersonnel and antitank mines. DuPont, which invented, manufactures, and sells Kevlar (as well as other household compound names such as Teflon) supplies its textile-like substance to manufacturers of boots that are specially designed to partially absorb a blast triggered by one of these mines. Combat engineer battalions and civilian volunteer units that have been assigned to clear out a minefield employ these boots.
Any chemistry student would be grateful for his lab to supply him or her with a pair of Kevlar gloves and sleeves. The material is extremely chemically resistant, showing weakness only when reacted with strong aqueous acids, bases, and sodium hypochlorite over long periods. By employing Kevlar in a mixture with nytril, PVC, rubber, or other coatings, the chemical resistance, cut resistance and toughness of the gloves are elevated even more.
As you have discovered, many components contribute to the strength of Kevlar. These include the fact that Kevlar is a polymer containing aromatic and amide molecular groups. When the molten Kevlar is spun into fibers, the polymers have a crystalline arrangement, with the polymer chains oriented parallel to the fiber’s axis. The amide groups are able to form hydrogen bonds between the polymer chains, which act like glue holding the separate polymer chains together. There is no end in sight to the list of possible applications for this materiel. Any substance that can stop bullets and cars and start new space programs to carry us to the stars and beyond in a period of three decades deserves accolades and attention.