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Aramid Fibers

In the 1960’s, scientists working at DuPont made exciting discoveries in the laboratory that led to the development of two new high-strength, lightweight, flexible and flame-resistant synthetic fibers called Nomex® and Kevlar®. Both these fibers are defined as aramids because they have molecular structures with incredibly stiff polymer chains that are linked together by close and ultra-strong hydrogen bonds. The name aramid is a portmanteau of the terms “aromatic” and “polyamide”. Two distinct types of aramids exist: meta-aramids (such as Nomex) and para-aramids (such as Kevlar). Today, aramids are mostly used in composite reinforcement and protective fabric applications. 

Protective gear made of kevlar

Aramid Fiber Structure

Aramid Fibers are used in protective gear

Aramid Fiber Structure

Properties

The polymers in aramid fibers contain phenol rings that are linked together by amide groups: this unique structure gives aramids their ultimate strength. In fact, the fibers are considered 4-5 times stronger than steel. They are also heat and solvent resistant. Aramids don’t melt and rarely burn but they can decompose. A high crystallinity eliminates any significant shrinkage, even when exposed to heat. Aramids are non-conductive and absorption-resistant.  Qualities particular to meta-aramids (Nomex) include ultraviolet resistance and formability for modular components. Para-aramids, on the other hand, are tough, structurally rigid and have a particularly high cut resistance.

 

Production and Processing Aramids Fibers

The most common process used to create aramids is hand lay-up molding, which involves applying a gel coating, a resin coating and a reinforcement layer to a mold, adding layers as required, curing, releasing and trimming. Vacuum bagging or infusion can also supplement the hand lay-up process. Other processing methods include injection molding, vacuum-assisted RTM, press molding, filament winding or pultrusion. Many of these processes require two molds, one for each side of the component, which are later adhesed to each other.

Applications

The remarkable heat-resistance and high strength-to-weight ratio have made aramids incredibly popular for use in protective gear (e.g. for firefighting) and body armor, including the bulletproof vests worn by police officers. In marine applications, aramid fibers form sailing ropes and sail cloths, admired for their low weight and high strength. Racing vehicle tires contain aramid because they are durable, light and comfortable for the driver, they resist wear and friction effectively and reduce fuel consumption compared to other types of racing tires. Aramids are commonly used to replace asbestos in construction and fireproofing. Other application areas include tennis strings, reeds for wind instruments, optical fiber cables, and snowboards.

  • Protective Gear
  • Sailing Ropes
  • Racing Vehicle Tires
  • Replacement for asbestos
  • Snowboards

Advantages

  • High strength
  • Low weight
  • Impact and abrasion-resistant
  • Won’t melt or burn in regular environments
  • Non-conductive