KEVLAR®

KEVLAR® is one of the most important man-made organic fibers ever developed. Because of its unique combination of properties, KEVLAR is used today in a wide variety of industrial applications. KEVLAR para-aramid fiber possesses a remarkable combination of properties that has led to its adoption in a variety of end uses since its commercial introduction in the early 1970s.

Fibers of KEVLAR consist of long molecular chains produced from poly-paraphenylene terephthalamide. The chains are highly oriented with strong interchain bonding, which result in a unique combination of properties.

General Features:

High tensile strength at low weight
Low elongation to break
High modulus (structural rigidity)
Low electrical conductivity
High chemical resistance
Low thermal shrinkage
High toughness (work-to-break)
Excellent dimensional stability
High cut resistance
Flame resistant, self-extinguishing

Adhesives and Sealants
Thixotropes

Ballistics and Defense
Anti-mine boots
Gloves - Cut-resistant police and military
Composite helmets
Vests - Bullet and fragmentation

Belts and Hoses
Automotive heating/cooling systems
Automotive and industrial hoses
Automotive and industrial synchronous and power Transmission belts

Composites
Aircraft structural body parts and cabin panels
Boats
Sporting goods

Fiber Optic and Electromechanical Cables
Communication and data transmission cables
Ignition wires
Submarine, aerostat, and robotic tethers

Friction Products and Gaskets
Asbestos replacement
Automotive and industrial gaskets for high-pressure and high-temperature environments
Brake pads
Clutch linings

Protective Apparel
Boots
Chain saw chaps
Cut-resistant industrial gloves
Helmets - Fireman and consumer (bicycle)
Thermal and cut-protective aprons, sleeves, etc.

Tires
Aircraft
Automobiles
Off-road
Race
Trucks

Ropes and Cables
Antennae guy wires
Fish line
Industrial and marine utility ropes
Lifting slings
Mooring and emergency tow lines
Netting and webbing
Pull tapes

Characteristics that Contribute to the Strength of Kevlar

KEVLAR is a long, chain-like molecule known as a polymer, which consists of repeating units called monomers.

A KEVLAR fiber is an array of molecules oriented parallel to each other like a package of uncooked spaghetti. This orderly, untangled arrangement of molecules is described as a crystalline structure. Crystallinity is obtained by a manufacturing process known as spinning, which involves extruding the molten polymer solution through small holes. The crystallinity of the KEVLAR polymer strands contributes significantly to KEVLAR's unique strength and rigidity.

KEVLAR is a polyaromatic amide. That is, it contains aromatic and amide groups. Other polymers with a high breaking strength often contain one or both of these molecular groups.

The individual polymer strands of KEVLAR are held together by hydrogen bonds that form between the polar amide groups on adjacent chains.

The aromatic components of KEVLAR polymers have a radial (spoke-like) orientation, which gives a high degree of symmetry and regularity to the internal structure of the fibers. This crystalline-like regularity is the largest contributing factor in the strength of KEVLAR. Only with bright synchrotron radiation could the secret strength of KEVLAR be revealed.

As you have discovered, there are many components that contribute to the strength of KEVLAR, including 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. The most recent XANES images confirm that the aromatic components of KEVLAR have a radial (spoke-like) orientation, which allows for a high degree of symmetry and order.