UHMWPE Fiber and Its Excellent Properties
UHMWPE has a unique structure that gives it outstanding physical and chemical properties, but the flexible linear macromolecular backbone structure of UHMWPE and its extremely high molecular weight (long molecular backbone) also constrain the forming process of this material. Because its molecular chains are long, UHMWPE macromolecular chains remain highly coiled and entangled after melting, resulting in excessively high viscosity in the molten state; instead of forming a viscous flow state they exhibit a highly elastic state, with a melt index of almost 0. They therefore cannot be processed and formed by the hot-melt extrusion and spinning methods commonly used for polyethylene. At the same time, UHMWPE in the highly elastic state has a low critical shear rate and very high melt viscosity, so in extrusion or injection molding the product surface is prone to unevenness, kinking, roughness and melt fracture — further factors that make the material difficult to process. Compared with conventional fibers, the most notable features of UHMWPE fiber are its ultra-high tensile strength and tensile modulus, its low density, and its high impact resistance based on a flexible chain structure. In addition, UHMWPE fiber offers excellent insulation, low-temperature resistance, chemical stability and hydrophobicity.
Excellent Mechanical Properties of UHMWPE Fiber
UHMWPE fiber has excellent mechanical properties. At the same linear density, the tensile strength of UHMWPE fiber is 15 times that of steel wire rope, 40% higher than aramid fiber, and 10 times that of high-quality steel fiber and ordinary composite fiber. Compared with steel, E-laminated glass, nylon and polyene amide, it has higher strength and modulus, and the highest strength among raw materials of the same mass.
UHMWPE Fiber Has Excellent Density and Specific Strength
The density of UHMWPE fiber is about 0.95 g/cm3 to 0.98 g/cm3. Compared with carbon fiber and aramid fiber, it has a lower density that is less than the density of water. Similar to polypropylene, it is a special high-performance fiber with a density lower than water.
UHMWPE fiber is a lightweight, high-strength fiber whose specific strength far exceeds that of other special polymer fibers, chiefly carbon fiber and aramid.