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Ultra High Molecular Weight Polyethylene (UHMWPE) Fibers

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*4/18/2012

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Ultra High Molecular Weight Polyethylene (ULMWPE)

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1. “Dyneema and Spectra are gel spun through a spinneret to form oriented-strand synthetic fibers of UHMWPE, which have yield strengths as high as 2.4 GPa (350,000 psi) and specific gravity as low as 0.97 (for Dyneema SK75).[8] High-strength steels have comparable yield strengths, and low-carbon steels have yield strengths much lower (around 0.5 GPa). Since steel has a specific gravity of roughly 7.8, this gives strength-to-weight ratios for these materials in a range from 8 to 15 times higher than steel. Strength-to-weight ratios for Dyneema are about 40% higher than for aramid.

 UHMWPE fibers are used in armor, in particular, personal armor and on occasion as vehicle armor, cut-resistant gloves, bow strings, climbing equipment, fishing line, spear lines for spearguns, high-performance sails, suspension lines on sport parachutes and paragliders, rigging in yachting, kites, and kites lines for kites sports. Spectra is also used as a high-end wakeboard line.

For personal armor, the fibers are, in general, aligned and bonded into sheets, which are then layered at various angles to give the resulting composite material strength in all directions.[9][10] Recently developed additions to the US Military's Interceptor body armor, designed to offer arm and leg protection, are said to utilize a form of Spectra or Dyneema fabric.[11] Dyneema provides puncture resistance to protective clothing in the sport of fencing.

Spun UHMWPE fibers excel as fishing line, as they have less stretch, are more abrasion-resistant, and are thinner than traditional monofilament line.

In climbing, cord and webbing made of combinations of UHMWPE and nylon yarn have gained popularity for their low weight and bulk, though, unlike their nylon counterparts, they exhibit very low elasticity, making them unsuitable for limiting forces in a fall. Also, low elasticity translates to low toughness. The fiber's very high lubricity leads to poor knot-holding ability, and has led to the recommendation to use the triple fisherman's knot rather than the traditional double fisherman's knot in 6mm UHMWPE core cord to avoid a particular failure mechanism of the double fisherman's, where first the sheath fails at the knot, then the core slips through.[12][13]

Owing to its low density, ships' hawsers and cables can be made from the fibre, and float on sea water. "Spectra Wires" as they are called in the towboat community are commonly used for face wires as a lighter alternative to steel wires.

It is used in skis and snowboards, often in combination with carbon fiber, reinforcing the fiberglass composite material, adding stiffness and improving its flex characteristics. The UHMWPE is often used as the base layer, which contacts the snow, and includes abrasives to absorb and retain wax.

It is also used in lifting applications for manufacturing low weight, and heavy duty lifting slings . Due to its extreme abrasion resistance it is also used as an excellent corner protection for synthetic lifting slings.

High-performance lines (such as backstays) for sailing and parasailing are made of UHMWPE, due to their low stretch, high strength, and low weight.[14]

Dyneema was used for the 30-kilometre space tether in the ESA/Russian Young Engineers' Satellite 2 of September, 2007.

The extremely low friction coefficient of UHMWPE makes it a common topsheet for boxes in terrain parks.

(Wikipedia, UHMWPE Fibers, 4/18/2012)

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Copyright 2012 by Roger D. Corneliussen.
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* Date of latest addition; date of first entry is 4/18/2012.

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