| 摘要 |
Polyethylene solutions are extruded through a multi-orifice spinneret into a cross-flow gas stream to form a fluid product. The fluid product is stretched at a temperature at which a gel will form at a stretch ratio of at least 5:1 over a length of less than about 25 mm with the cross-flow gas stream velocity at less than about 3 m/min. The fluid product is quenched in a quench bath consisting of an immiscible liquid to form a gel. The gel is stretched. The solvent is removed from the gel to form a xerogel and the xerogel product is stretched in at least two stages to produce a polyethylene yarn characterized by a tenacity of at least 35 g/d, a modulus of at least 1600 g/d and a work to break of at least 65 J/g. The yarn is further characterized by having greater than about 60% of a high strain orthorhombic crystalline component and, optionally, a monoclinic crystalline component greater than about 2% of the crystalline content. Composite panels made with these yarns exhibit excellent ballistic resistance, e.g., SEAC of 300 J-m<2>/Kg or higher against .38 caliber bullets using test procedure NILECJ-STD-0101.01.A ballistic resistant composite panel is provided comprising a polyethylene multi-filament yarn having a tenacity of at least about 35 g/d, a modulus of at least 1600 g/d, a work-to-break of at least about 65 J/g wherein the yarn has greater than about 60% of a high strain orthorhombic crystalline component and the yarn has a monoclinic crystalline component greater than about 2% of the crystalline content.
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