Molecular structure
The Dyneema® fiber originates from an Ultra High Molecular Weight Polyethylene solvent spinning process. Stretching the fiber introduces molecular alignment and a high level of crystallinity.
Having a density of less than one provides the basis for the fiber’s light weight and high strength, as well as for its low elongation. Diameter for diameter, the strength and elongation of products made with Dyneema® are comparable to that of steel, with only 15% of the weight. In marine and industrial applications, Dyneema® is the fiber with the highest strength-to-weight ratio. Also, the low-friction properties of the fiber protect it from internal abrasion, resulting in long service lives in rope tensile- and bending fatigue testing.
Thermal properties
Like other synthetic fibers, the mechanical properties of UHMWPE fibers are influenced by temperature. The strength and modulus increase at sub-ambient temperatures and decrease at higher temperatures. For long duration exposure UHMWPE fiber from DSM can be used from cryogenic conditions up to a temperature of 70°C.
Dyneema® fiber has a melting point between 144oC and 152oC. The tenacity and modulus decrease at higher temperatures but increase at sub-zero temperatures. There is no brittle point found as low as -150oC, so the fiber can be used between this temperature and 70oC. Brief exposure to higher temperatures will not cause any serious loss of properties.
Static load
With increasing static load and temperature, the Dyneema® fiber elongates irreversibly. This is called creep. Among the commercial available HMPE fibers, Dyneema® shows the lowest creep with the longest creep life. DSM has developed a widely accepted model for accurate creep calculations. These calculations support the search for applicability of the Dyneema® fiber in most applications.
Mechanical properties
UHMWPE fibers have a high strength and a high modulus (resistance against deformation) in the fiber direction. In combination with the low density this results in an extremely high strength on weight basis, making it one of the strongest man-made fibers.
The elongation at break is relatively low, but owing to the high strength, the energy to break is high. In contrast to other synthetic fibers, the mechanical properties are not influenced by the presence of water. Due to the anisotropic nature of high modulus polyethylene fibers, the modulus and strength in transverse direction are lower than in fiber direction.
Subjecting UHMWPE fiber to long-term static loads leads to a permanent elongation called creep. The UHMWPE fiber types from DSM have a higher creep resistance than other UHMWPE fibers enabling their use in various static loading conditions.
Chemical resistance
UHMWPE fiber is very resistant against chemicals. Because it is produced from ultra-high molecular weight polyethylene, it does not contain any aromatic rings or any amide, hydroxylic or other chemical groups that are susceptible to attack by aggressive agents.
