Kevlar

media type="youtube" key="1dOAtZ6m3Bg" height="385" width="477" media type="youtube" key="4x8AJYDrFlU" height="157" width="199" KEVLAR PRODUCTION ! media type="youtube" key="gPKbOrxgx-w" height="159" width="200" There are two main steps in making Kevlar. The first step is producing the basic plastic from which Kevlar is made which is a chemical called **poly-para-phenylene terephthalamide.** Second, is turning it into strong fibres. Basically, the first step is all about chemistry and the second one, about turning the chemical product into a more useful, practical material. media type="youtube" key="UhEmu4Kg1Rk" height="611" width="784"

Just like the production of nylons, Kevlar filaments are produced by extruding the precursor through a spinneret. The rod form of the para-aramid molecules and the extrusion process make Kevlar fibres anisotropic – which means that that they are stronger and stiffer in the axial direction than in the transverse direction. In comparison, graphite fibres are also anisotropic, but glass fibres are isotropic.

Polyamides like Kevlar are polymers made by repeating amides over and over again. By the way, polymers are large molecules composed of repeating structural units typically connected by covalent chemical bonds. Although polymers large class of natural and synthetic materials with a wide variety of properties. Amides are simply chemical compounds in which part of an organic (carbon-based) acid replaces one of the hydrogen atoms in ammonia (NH3). Amides are amine derivatives of carboxylic acids. 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. In other words, Kevlar is synthesized from the monomers 1,4-phenyl-diamine ( // para // -phenylenediamine) and terephthaloyl chloride. The result is a polymeric aromatic amide (aramid) with alternating benzene rings and amide groups. When they are produced, these polymer strands are aligned randomly. To make Kevlar, they are dissolved and spun, causing the polymer chains to orient in the direction of the fibre. Kevlar has a high price at least partly because of the difficulties caused by the use of concentrated sulfuric acid in its manufacture. These harsh conditions are needed to keep the highly insoluble polymer in solution during synthesis and spinning.


 * **Grade** || **Density g/cm3** || **Tensile Modulus GPa** || **Tensile Strength GPa** || **Tensile Elongation %** ||
 * 29 || 1.44 || 83 || 3.6 || 4 ||
 * 49 || 1.44 || 131 || 3.6 – 4.1 || 2.8 ||
 * 149 || 1.47 || 186 || 3.4 || 2 ||

How Can It Affect Us?

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, for boatbuilding, in the strings of archery bows, and in car, boat, and even aircraft bodies. It's even used as a tough, durable building material.

The worldwide recognition Kevlar® brand fiber has earned as a high-performance material for helping to protect human life extends far beyond the body armor used by the military and law enforcement community. A unique combination of properties makes Kevlar® the first choice for an ever-growing number of applications where a reduction of weight, increase in strength and resistance to corrosion produce significant improvements in safety and efficiency. Today, Kevlar® is used in everything from airplane parts to reinforced suspension bridge structures to suspension bridge cables to fiber optic cables, not to mention a variety of consumer goods. Chances are you either use Kevlar® or come into contact with it on a regular basis.

DuPont™ Kevlar® is a para-aramid (aromatic polyamide) fibre that comes in different forms, each suited to a specific set of consumer and industrial applications. DuPont offers Kevlar® in the form of cut fibre that can be converted into yarn or thread, continuous filament yarn, fibrillated pulp, and sheets that provide the structure for mechanical paper. As our customers continue to use Kevlar® to help enhance performance and increase safety, DuPont works with them to explore new possibilities for Kevlar® innovations.

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Products:
 * Aramid Pulp
 * Fibre & Filament
 * Fire-Resistant Mattresses
 * Paper for Aerospace Applications
 * Spun Yarn Felt
 * Life Protection Products
 * Stormroom
 * Future Fibre Technologies

Uses and Applications:
 * Body Armour
 * Protection Vests
 * Military Helmets
 * Heat Resistant Gloves
 * Vehicle Armour
 * Multiple Threat Protection
 * Automotive
 * Mass transportation
 * Fibre Optics
 * Ropes and Cables
 * Adhesive, Sealants & Coatings:
 * Composites
 * Oil and Gas
 * Industrial gloves and apparel
 * Consumer applications

These are some of Kevlar's properties (which are pretty interesting) : Kevlar® brand fiber is an innovative technology from DuPont that combines high strength with light weight to help dramatically improve the performance of a variety of consumer and industrial products. Groundbreaking research by DuPont scientists in the field of liquid crystalline polymer solutions in 1965 formed the basis for the commercial preparation of the Kevlar® aramid fibre.
 * It's strong but relatively light (the specific tensile strength of both Kevlar 29 and Kevlar 49 is over eight times greater than that of steel wire).
 * Unlike most plastics it does not melt: it's reasonably good at withstanding temperatures and decomposes only at about 450°C (850°F).
 * Unlike its sister material, Nomex, Kevlar can be ignited but burning usually stops when the heat source is removed.
 * Very low temperatures have no effect on Kevlar: DuPont found "no embrittlement or degradation" down to -196°C (-320°F).
 * Like other plastics, long exposure to ultraviolet light (in sunlight, for example) causes discoloration and some degradation of the fibers in Kevlar.
 * Kevlar can resist attacks from many different chemicals, though long exposure to strong acids or bases will degrade it over time.
 * In DuPont's tests, Kevlar remained "virtually unchanged" after exposure to hot water for more than 200 days and its super-strong properties are "virtually unaffected" by moisture.

**Catching bullets**
Body armour made with DuPont™ Kevlar® brand fiber works by 'catching' a bullet in a multilayer web of woven fabrics. Just as different Kevlar® fabrics are tailored to specific threats, different layers in the weave have different tasks—from engaging a fast-moving, undeformed projectile to completely stopping the blunted bullet.

**Engaged fibres absorb energy**
The engaged fibers absorb and disperse the energy of the impact, transferring it to other fibers at 'crossover points' in the weave. These fibers continue to absorb energy, reducing the force that causes 'blunt trauma'.

**Comfort and protection**
These woven fabrics are strong enough to resist a bullet, yet more comfortable than traditional plastic-based shield products. Fabrics made from light-denier yarns offer enhanced protection and comfort features. The highest-performing, lightest-weight vests are made with light-denier Kevlar®. Whatever protective vest technology you're looking for, vests with Kevlar® can meet your performance, comfort and cost requirements.

Sources: __http://en.wikipedia.org/wiki/Amide http://en.wikipedia.org/wiki/Polymer http://composite.about.com/od/aboutcompositesplastics/l/aa050597.htm http://www.experiencefestival.com/a/Kevlar_-_Production/id/5548278__ __ http://www.explainthatstuff.com/kevlar.html  ( Done by Chris Woodford Copyright @ 2009 ) __ __http://www.body-armour-protection.co.uk/buy/interesting-facts.html []__