Aramid yarns

Aramid Yarn—Strength elements that provide tensile strength and provide support and additional protection of the fiber bundles. Kevlar is a particular brand of aramid yam. 

There are a few elastomer reinforcement applications where w-aramid yarns are superior to p-aramid yarns. Continuous filament w-aramid yarn is used in a loose knit construction to reinforce automotive heater hose. Yarn on yarn abrasion resistance, and not strength, is key to performance in this application where the hose is exposed to significant thermal, impulse, and vibrational stresses. A second growing use is in the reinforcement of silicone elastomer hose for automobile turbochargers where j-aramid provides high thermal stability. 

Cut-resistant gloves are fabricated from a cut-resistant composite yarn having a core yarn and a first wrapping yarn helically wrapped around the core yarn. The core is of 56-220 dtex glass fiber filament yarn. The first wrapping is a 110-680 dtex para-aramid yarn. An additional yarn is made from aliphatic polyamides or polyesters. Further, the lining yarn is a composite yarn of 110-560 dtex of an elastomer [97]. 

Boerstoel H, Bos J, Schaap AA, Wilbers D, Busscher LAG, Schotman AHM, et al. Method for obtaining high-tenacity aramid yarn. US Patent 8501071, assigned to Teijin Aramid B.V., Arnhem, NL 2013. 

Figure 1 shows the result of our experiments on aramid yarns with... 

E. I. du Pont de Nemours Co., Inc., Properties and Processing of DuPont KEVLAR Aramid Yarn for Mechanical Rubber Goods, A-88950, June 1993. 

Schwarz, A., et al., 2009. How to equip para-aramide yarns with electro-conductive properties. In Sixth International Workshop on Wearable and Implantable Body Sensor Networks, 2009. BSN 2009, pp. 278-281. 

You may become curious and study some yarns with a magnifying glass and discover that single fibers are as thin as 10-30 pm. With a pair of tweezers you unravel the structure and pull out fibers a few centimeters in length or discover that in some cases the fibers have infinite length. You may test yams by pulling them between your hands - and cut your fingers when it is an aramid yarn ... 

Aramid yarns (Kevlar of DuPont, Twaron of Teijin-Twaron) are produced from poly(p-phenylene terephthalamide), PPTA (2), which is specially developed for fiber spinning and not used in any other application. DuPont had experience with poly(m-phenylene isophthalamide) in a fiber product called Nomex for high-temperature applications. The polymer is produced in dimethylacetamide and the solution is dry-spun. This cannot be done with the stiff-chain para-para analogue PPTA. The polymer does not dissolve in organic solvents. A special polymerization route had to be developed, and the discovery of lyotropic behavior of concentrated solutions in sulfuric acid then led the way to the production of a magnificent new fiber material. 

Thus, the rest of the spinning process is careful washing, neutralization, further washing, drying, and winding. The standard titer of aramid yarns is 1670 dtex f 1000 (1.7 dtex filament titer). The elongation at break is around 3%, the tenacity 2100 mN tex , and the modulus > 50 N tex (75 GPa). 

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