What Is Ultra-High Molecular Weight Polyethylene (UHMWPE) Fiber?
UHMWPE fiber is also known as high-strength, high-modulus polyethylene fiber, and is linear polyethylene with an unbranched chain and a molecular weight above 1.5 million. Together with carbon fiber and aramid it is called one of the “three major high-tech fibers in the world.”
UHMWPE fiber is the strongest and toughest fiber in the world. In plain terms, it is “as light as paper and as hard as steel”; its strength is 15 times that of steel, and it is currently the main material for manufacturing ballistic vests.
01. Excellent Mechanical Properties of UHMWPE Fiber
At the same linear density, the tensile strength of UHMWPE fiber is 15 times that of steel wire rope. It is 40 percent higher than aramid, another of the “three major high-tech fibers in the world,” and 10 times higher than high-quality steel fiber and ordinary chemical fiber. Compared with steel, E-glass, nylon, polyene amide, carbon fiber and boron fiber, it has higher strength and modulus, and the highest strength among materials of the same mass.
02. Excellent Impact Resistance of UHMWPE Fiber
UHMWPE fiber has excellent impact resistance; its capacity to absorb energy during deformation and shaping and its ability to resist impact are higher than those of aramid fiber and carbon fiber, also among the “three major high-tech fibers in the world.” Compared with polyamide, aromatic polyamide, E-glass fiber, carbon fiber and aramid, UHMWPE fiber has an even higher total absorbed impact energy.
03. Excellent Abrasion Resistance of UHMWPE Fiber
Comparing the friction coefficients of reinforced plastics made from UHMWPE fiber, carbon fiber and aramid fiber, the abrasion resistance and flexural fatigue resistance of UHMWPE fiber are far higher than those of carbon fiber and aramid fiber. Its abrasion resistance is therefore better than that of other high-performance fibers. Because of its superior abrasion resistance and bending resistance, its processing performance is also superior, and it is easy to make into other composite materials and fabrics.
04. Chemical Corrosion Resistance of UHMWPE Fiber
UHMWPE fiber has a relatively simple chemical structure and is chemically stable. Most chemicals do not readily corrode it; only a very small number of organic solutions can cause slight swelling, and the loss of mechanical properties is less than 10 percent. Comparing the strength retention of UHMWPE fiber and aramid fiber in different chemical media, the corrosion resistance of UHMWPE fiber is markedly higher than that of aramid fiber. It is particularly stable in acids, alkalis and salts, with some strength loss only in sodium hypochlorite solution.
05. Good Light Resistance of UHMWPE Fiber
Because UHMWPE fiber has a stable chemical structure, its light resistance is also the best among high-tech fibers. Aramid fiber is not resistant to ultraviolet light and can only be used where direct sunlight is avoided. Comparing UHMWPE fiber with nylon and with high-modulus and low-modulus aramid, the strength retention of UHMWPE fiber is markedly higher than that of the other fibers.
06. Other Properties of UHMWPE Fiber
UHMWPE fiber also has good hydrophobic performance, water and moisture resistance, electrical insulation and a long flex life. Its water resistance and low-temperature resistance are outstanding, its specific gravity is low, and it is the only high-tech fiber that can float on water; it is also a relatively ideal low-temperature material. However, it has a drawback: a relatively low melting point. During processing the temperature must not exceed 130 ℃, otherwise creep will occur, because the intermolecular forces between UHMWPE fiber chains are weak, shortening the service life. UHMWPE fiber has no dye sites, which gives it poor wettability — dyes can hardly penetrate into the fiber, resulting in poor dyeability. These drawbacks have limited the scope of its applications.