As a fibrous material, Kevlar enables manufacturers to create products that are flexible, yet strong. Kevlar is ideal for clothing applications, since it can be cut and sized into shapes that are form-fitting.
As such, Kevlar is perfect for gloves, protective coats, and more. Kevlar is an ideal body armor material, since its fibers are incredibly difficult to break again, thanks to its tensile strength. The linked chain fibers of Kevlar absorb high-velocity impacts, instead of enabling a ballistic to penetrate the material. This feature makes Kevlar ideal for military and police applications, including body armor and vests.
DuPont currently produces a variety of types of Kevlar, including XP and XD Kevlar, which are specifically designed for use as a ballistics material. These materials have even greater strength against ballistics, and the material can be layered and configured as desired to enhance its protective qualities, weight, or flexibility.
Kevlar cannot be easily cut or punctured, due to the chain links that form the fibers of this material. That means even more protection for police and military applications.
In addition, it makes Kevlar the ideal material for a variety of gloves, where workers handle sharp objects. This chemical is made from creating a chemical reaction between an acid and a chemical solution containing nitrogen and hydrogen.
This process results in chemical chains composed of hydrogen, carbon, oxygen, and nitrogen. Kevlar fibers are based on poly-paraphenylene terephthalamide, a rigid molecule that makes it easier to realize a fully extended, or straight, chain configuration. Also, these rigid molecules will even arrange in solutions. Such solutions are called liquid crystalline, which underscores their good organization. Poly-paraphenylene terephthalamide molecules behave like uncooked spaghetti, whereas other, less rigid molecules behave more like cooked strands of spaghetti.
Thus, the nature of the molecule makes it easier to achieve the desired aligned structure. In addition, poly-paraphenylene terephthalamide strongly resists high temperatures and flames. Offering strength under heat, Kevlar protects against thermal hazards up to degrees Farenheit.
This combination of unusual properties makes Kevlar useful for a broad range of applications, such as ballistic vests, cut-resistant gloves and blast and flame barriers. Kevlar has also boosted sports gear performance. Applications in that vein include bicycle tires that are virtually flat-free and puncture-resistant; running shoes that maximize the energy output of runners; boats that are lighter and more damage-tolerant; and durable lightweight sails that tolerate high winds and saltwater.
Originally published on September 30, Sign up for our email newsletter. In its chemical structure, it's very similar to another versatile protective material called Nomex. Kevlar and Nomex are examples of chemicals called synthetic ar omatic poly amid e s or aramids for short. Calling Kevlar a synthetic aromatic polyamide polymer makes it sound unnecessarily complex. Things start to make more sense if you consider that description one word at a time:.
Photo: Super-strong Kevlar is best known for its use in body armor. Picture by Lcpl Joseph A. Stephens courtesy of United States Marine Corps. It's worth noting that Kevlar also has its drawbacks.
In particular, although it has very high tensile pulling strength, it has very poor compressive strength resistance to squashing or squeezing. There are two main stages involved in making Kevlar. First you have to produce the basic plastic from which Kevlar is made a chemical called poly-para-phenylene terephthalamide —no wonder they call it Kevlar.
Second, you have to turn it into strong fibers. So the first step is all about chemistry; the second one is about turning your chemical product into a more useful, practical material. Polyamides like Kevlar are polymers huge molecules made of many identical parts joined together in long chains made by repeating amides over and over again.
Amides are simply chemical compounds in which part of an organic carbon-based acid replaces one of the hydrogen atoms in ammonia NH3. So the basic way of making a polyamide is to take an ammonia-like chemical and react it with an organic acid. This is an example of what chemists call a condensation reaction because two substances fuse together into one. This basic building block is repeated over and over again in the very long chains that make up the Kevlar polymer.
Source: "US Patent: Process for the production of a highly orientable, crystallizable, filament" by Stephanie Kwolek et al. Kevlar's chemical structure naturally makes it form in tiny straight rods that pack closely together, like lots of stiff new pencils stuffed tightly into a box only without the box.
These rods form extra bonds between one another known as hydrogen bonds giving extra strength—as though you'd glued the pencils together as well.
This bonded rod structure is essentially what gives Kevlar its amazing properties. More technically speaking, we can say the Kevlar rods are showing what's called nematic behavior lining up in the same direction , which is also what happens in the liquid crystals used in LCDs liquid crystal displays.
You probably know that natural materials such as wool and cotton have to be spun into fibers before they can turned into useful textile products—and the same is true of artificial fibers such as nylon, Kevlar, and Nomex. The basic aramid is turned into fibers by a process called wet spinning , which involves forcing a hot, concentrated, and very viscous solution of poly-para-phenylene terephthalamide through a spinneret a metal former a bit like a sieve to make long, thin, strong, and stiff fibers that are wound onto drums.
The fibers are then cut to length and woven into a tough mat to make the super-strong, super-stiff finished material we know as Kevlar. Artwork: How Kevlar is made.
At this stage, the molecules are still tangled up and not extended into straight, parallel chains. Kevlar can be used by itself or as part of a composite material one material combined with others to give added strength. It's probably best known for its use in bulletproof vests and knifeproof body armor, but it has dozens of other applications as well. It's used as reinforcement in car tires, in car brakes , in the strings of archery bows, and in car, boat, and even aircraft bodies.
It's even used in buildings and structures, although not because of its relatively low compressive strength as the primary structural material. Photo: Think of Kevlar as a lightweight modern alternative to heavy, cumbersome, medieval suits of armor! Photo by Staff Sgt.
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