Dyneema
Dyneema is a
synthetic fiber based on
ultra high molecular weight polyethylene, 15 times stronger than steel and up to 40% stronger than
Kevlar. It is usually used in
bulletproof vests,
bow strings, climbing equipment,
fishing line and high performance
sails in
yachting. Dyneema was invented by
DSM in
1979. It has been in commercial production since
1990 at a plant in
Heerlen, the
Netherlands. In the
Far East, DSM has a cooperation agreement with
Toyobo Co. for commercial production in
Japan. In the
United States, DSM has granted a license to
Honeywell, which had developed a chemically identical product on its own. The Honeywell product is sold under the brand name
Spectra. Though the production details will undoubtedly be different, the resulting materials are comparable. This article refers to both materials by the name Dyneema.
Dyneema is a registered trademark of Royal DSM N.V. (The Netherlands).
For details, see the properties section of Ultra high molecular weight polyethylene.Dyneema fibers derive their strength from the extreme length of each individual molecule. The fibre can attain a parallel orientation greater than 95% and a level of
crystallinity of up to 85%. In contrast,
Kevlar derives its strength from strong bonding between relatively short molecules.
Its
melting point is around 144 or 152 degrees
Celsius, and according to DSM, it is not advisable to use Dyneema at temperatures exceeding 80 to 100 °C for long periods of time. It becomes
brittle at temperatures below â€"150 °C. This contrasts strongly with other high-performance fibers, which tend to be quite heat-resistant.
The fibers feel slippery, similar to
polypropylene and other
hydrophobic fibers. Most people do not like the way Dyneema feels; for this reason, it is not often used in fabric. The slipperiness also makes such fibers less suitable for use in
fibre reinforced plastics.
Another problem, in some applications, is that Dyneema will
creep, meaning it will deform when placed under any long term stress. Like other
olefins, it is very resistant to water, moisture, most chemicals, UV radiation, and micro-organisms.
Dyneema fibers are made using a DSM patented (1979) method called
gel spinning. A precisely heated gel of
UHMWPE is processed by an
extruder through a
spinneret. The extrudate is drawn through the air and then cooled in a water bath. The end result is a fiber with a high degree of molecular orientation, and therefore exceptional
tensile strength.
For
body armor, the fibers are generally aligned and bonded into sheets, which are then layered at various angles to give the resulting
composite material strength in all directions.
Both Spectra and Dyneema excel as
fishing line as they have less stretch, are more
abrasion resistant, and are thinner than traditional
monofilament line.
In recent years certain items of
climbing equipment have started making use of Dyneema. In particular "
slings", sewn loops of material that can be wrapped around sections of rock,
hitched (tied) to other pieces of equipment or even tied directly to a tensioned line using a special
prussik knot, have benefited from this material. It has limited applications however as items made from this material do not stretch and therefore a fall on them involves considerable shock loading of the other pieces of equipment and the climber's body. They are however much lighter and finer than the alternatives (
nylon) and therefore are very popular. Usually sold in lengths of 10, 30, 60, 120, or 400 cm at either 8, 10 or 12 mm width, these slings have a breaking strength of around 22
kN.
High-performance ropes for
sailing and
parasailing are made of Dyneema as well.
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 Dyneema fabric.
It is also used in snowboards, often in combination with
carbon fiber, reinforcing the
fiberglass composite material, adding stiffness and improving its flex characteristics.
Dyneema is the preferred material for
sport kite lines for two main reasons. First the low stretch means that control inputs to the kite are transferred quickly and secondly the low friction allows the kite to remain controllable up to about ten twists in the line.
*
Olefin*
Ultra high molecular weight polyethylene*
Kevlar*
Synthetic fiber*
DSM Homepage*
Comparison of rope materials.*
Tote Systems Australia Dyneema Page
