What Is Kevlar Fabric?

By Neal Litherland, eHow Contributor


Kevlar, like many brand names for complicated items, isn't very well understood. This material is used popularly in bulletproof vests due to its intensely strong and hard-to-corrode weave. Just what this material is, however, and how it's made are issues that become much more complex to explain.




Definition
Kevlar is made of an extremely strong fabric called an aramid fabric, which is chemically related to nylon. This fabric, which is already very tough and durable, is then woven in a pattern similar to tiny spiderwebs all interlocked to provide additional strength and durability. Aramid fibers like kevlar are resistant to wear, tear and heat, and have absolutely no melting point.


Types
Like any compound, kevlar comes in a variety of different types. Kevlar 29 is the fabric that is woven to make bulletproof vests. However, kevlar 49 is harder and not at all fabric-like. This material can be used to make frames for bicycles or hulls for boats.


Process
Aramid fabrics like kevlar are made through a fairly intense chemical process. Kevlar in all its varieties is made from a polymer that's spun from hot, high-solids solutions of concentrated sulfuric acid. Any nylon fabric that needs to be tough, kevlar included, should be hot-drawn. That means that while the fabric is being made, the environment of the chemical reactions should be at a high temperature. Kevlar 29, for instance, is hot drawn at a temperature of more than 400 C.


Heat
Due to kevlar's high resistance to heat and inability to melt, it's often used in fire-fighting equipment. Nomex, which is a fabric that is generally considered to be fireproof, is a variant of kevlar fabric.


Other Uses
Kevlar fabric's properties make it a high demand item. Recently kevlar has been made an integral part of shelters in areas of high tornado occurrence. Kevlar's strength and endurance give it the ability to deflect even large items hitting a shelter and thus to protect people inside.