Explanation

It refers to the fiber made of polyethylene with a average molecular weight of more than 1 million. It is mainly made by gel spinning super drawing method. ultra high molecular weight polyethylene (UHMWPE) is dissolved in solvent to form solution, and then is spun by dry or wet gel spinning. Since the crystal structure of the fiber is relatively free during gel spinning, the fiber can be super stretched after solvent removal, which is easy to straighten the molecular chain, thus forming an ultra-high strength fiber. The key technology is to keep the dilute solution of polymer in liquid state at the spinning temperature. After spinning and extrusion, it passes through an air layer of 1-2 cm, and then enters the coagulation bath for rapid cooling to make gel fiber. Generally speaking, medium molecular weight polyethylene (400000-800000) can be used to prepare high-strength fibers, but the actual molecular weight is generally between 3 million and 5 million. The concentration of spinning solution is usually controlled between 5% and 10%. The spinning equipment can be standard solvent spinning equipment or screw extruder. The diameter of the spinning hole can be controlled within 0.5 to 1.0 mm, and the ratio of the length and diameter of the flow fields or flow channels can reach 25. The main brands of high-strength polyethylene fibers abroad include Dyneema and Spectra series. The density of this fiber is 0.97 g/cm 3， The tensile strength is 2.8 to 4.0 GPa, the elastic modulus is 80 to 140 GPa, the elongation is 3 to 5%, and the melting point is about 150 ° C. This fiber can be used to strengthen composite materials such as thermosetting resin, polyester, polyethylene ester or low-temperature thermoplastic phenolic resin (about 120 ° C), providing excellent impact performance and energy absorption performance. Because macromolecule polyethylene fiber also has good toughness, wear resistance, chemical resistance, non water absorption and low density, it can be used not only for impact resistant lightweight composite materials, but also for ropes, medical sutures, artificial tendons, bulletproof clothing, optical fiber reinforcing fiber, etc. The disadvantage is that its melting point is low, which may cause creep, and its adhesion to polymer is poor.

Classification