The UHMWPE fiber is a type of polyolefin fiber. The fibers are made up of extremely long chains of polyethylene, which are aligned in the same direction. Each chain is bonded to the other with many van der Waals bonds. This provides the superior physical properties attractive for a number of military and industrial applications.
The UHMWPE fiber polymer chains can attain an orientation greater than 95% and a level of crystallinity of up to 85%.
The weak bonding between olefin molecules allows local thermal excitations to disrupt the crystalline structure and therefore UHMWPE fibers have lower heat resistance than other high-strength fibers. The melting point of UHMWPE fibers is around 144–152°C and, generally, UHMWPE fibers are not used at temperatures exceeding 80–100°C for long periods of time. However, the UHMWPE fibers maintain performance at below −50°C.
Owing to the molecular structure of UHMWPE fibers, they exhibit surface and chemical properties that are rare in high-performance polymers and do not absorb water readily. For the same reason, skin does not interact with it strongly, making the UHMWPE fiber surface feel slippery. The UHMWPE fibers are resistant to water, moisture, most chemicals, ultraviolet (UV) radiation, and microorganisms.
The density of gel-spun UHMWPE fibers is 0.97 g/cm3.