Suspension spinning of ultra-high molecular weight polyethylene

Summary This note deals with the preparation of ultra-high strength polyethylene filaments by suspension spinning and subsequent hot-drawing at 148 °C. Suspension spinning involves the flow of stabilized suspensions of high molecular weight polyethylene powder in a solvent mixture through a long heated tube. In the tube, which acts as the spinning apparatus, the polyethylene is dissolved after which the polymer solution is spun in air. Under appropriate conditions of spinning and hot-drawing monofilaments were produced with a tensile strength at break of 3.8 GPa and a Young's modulus of 124 GPa.     

High-speed gel-spinning of ultra-high molecular weight polyethylene

Summary This communication is concerned with the gel-spinning of ultrahigh molecular weight polyethylene (UHMWPE) at speeds up to 1500 m/min. It was found that 5 wt% solutions of UHMWPE in paraffin oil could be extruded through a conical die at a rate of 100 m/min. without the appearance of filament irregularities due to elastic solution fracture. These elastic turbulences occur at extrusion speeds of about 5 m/min. Without the addition of 1 wt% of Aluminium-stearate the spinline could be stretched at most to 60 m/min at 170°C but at 210°C it did not break at a speed of 1500 m/min.These high-speed gel-spinning experiments at temperatures around 200°C yielded polyethylene fibers with a tensile strength of 3.5 GPa. It was observed that drying of the as-spun fiber containing n-hexane at constant length led to excessive crazing.     

凝胶纺丝法制备超高分子量聚乙烯/高分子量聚乙烯纤维延伸性能的研究

用凝胶纺丝法制备了超高分子量聚乙烯(UHMWPE)/高分子量聚乙烯(HDPE)纤维,探讨了添加不同种类高分子量聚乙烯对凝胶初生纤维在后续延伸过程中延伸性能的影响。结果表明在固定制备条件时,当超高分子量聚乙烯(UHMWPE)/高分子量聚乙烯(HDPE)的质量比在最适当质量比时,高分子量聚乙烯的分子量为1.5～2.0×104时,所制备的凝胶初生纤维的可延伸比达最大值。     

Short aramid-fiber reinforced ultra-high molecular weight polyethylene

Summary Ultra-High Molecular Weight Polyethylene (UHMWPE) is frequently used in artificial joints because of its high wear resistance. To extend the lifetime of these joints even further, it is necessary to decrease the wear rate. The wear rate may be decreased by blending UHMWPE with short aramid fibers. On account of the extremely high viscosity of UHMWPE mixing was accomplished by swirling the UHMWPE powder and the chopped fibers with compressed dry nitrogen, and a composite with fairly uniformly distributed and randomly oriented fibers was obtained by compression moulding. The failure behaviour of the composite changes from ductile for low fiber content to brittle failure for higher fiber content. The deviation of the experimental Young's modulus from the theoretical value can be explained by, among others, the void content. Preliminary results show that the wear rate of UHMWPE indeed decreases with incorporation of the aramid fibers.     

超高分子量聚乙烯纤维的表面处理

综述了超高分子量聚乙烯（UHMWPE）纤维复合材料界面的重要性,总结了表面改性方法对UHMWPE纤维以及UHMWPE／树脂界面的影响。     

Melting behavior of ultra-high modulus and molecular weight polyethylene (UHMWPE) fibers

Superheating and double-melting endotherms are the characteristic melting behaviors of gel-spun ultra-high modulus and molecular weight polyethylene (UHMWPE) fibers in differential thermal analysis (DTA). A mostly orthorhombic structure with very little amorphous content is indicated by wide angle x-ray scattering (WAXS) data. The melting temperatures are elevated and believed to result from superheating and incomplete chain relaxation in the highly oriented and crystalline structure. The melting behavior of the fibers is shown to be strongly affected by changes in polymorphic transformations and in intercrystalline disordered domains. Compression in the direction perpendicular to fiber axis causes significant increases in the 110 and 200 dimensions of the orthorhombic structure. Such lateral compression increases monoclinic forms and perhaps amorphous content, and decreases the degree of transformation to hexagonal phase. Superheating, which is related to the intercrystalline stress, can be reduced by the presence of interacting solvents such as trichlorbenzene. © 1994 John Wiley & Sons, Inc.     

UHMWPE／Epoxy冻胶体系的流变行为研究

研究了环氧树脂(Epoxy)加入后对超高分子质量聚乙烯(UHMWPE)稳态表观粘度、粘流活化能以及复数模量和粘度的影响。结果表明,环氧树脂添加量低于1ω,UHMWPE／Epoxy冻胶体系的表观粘度和粘流活化能都低于空白 UHMWPE冻胶体系;当环氧树脂添加量增加至3 ω以后,冻胶体系的表观粘度和粘流活化能均比空白UHMWPE冻胶体系高。     

Ultradrawing behavior of one- and two-stage drawn gel films of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends

The ultradrawing behavior of gel films of plain ultrahigh molecular weight polyethylene (UHMWPE) and UHMWPE/low molecular weight polyethylene (LMWPE) blends was investigated using one- and two-stage drawing processes. The drawability of these gel films were found to depend significantly on the temperatures used in the one- and two-stage drawing processes. The critical draw ratio (λ_c) of each gel film prepared near its critical concentration was found to approach a maximum value, when the gel film was drawn at an “optimum” temperature ranging from 95 to 105°C. At each drawing temperature, the one-stage drawn gel films exhibited an abrupt change in their birefringence and thermal properties as their draw ratios reached about 40. In contrast, the critical draw ratios of the two-stage drawn gel films can be further improved to be higher than those of the corresponding single-stage drawn gel films, in which the two-stage drawn gel films were drawn at another “optimum” temperature in the second drawing stage after they had been drawn at 95°C to a draw ratio of 40 in the first drawing stage. These interesting phenomena were investigated in terms of the reduced viscosities of the solutions, thermal analysis, birefringence, and tensile properties of the drawn and undrawn gel films. © 1998 John Wiley & Sons, Inc. J. Appl. Polym. Sci. 70: 149–159, 1998     

Ultradrawing behavior of gel films of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends at varying drawing conditions

A systematic study of the influence of the drawing temperature and rate on the ultradrawing properties of film samples prepared from gel solutions of ultrahigh molecular weight polyethylene and low molecular weight polyethylene blends is reported. At a fixed drawing rate, the achievable draw ratios reached a maximum value when each film specimen was drawn at a temperature near its optimum temperature (T_op). It is interesting to note that the T_op values of each film sample increased consistently with the drawing rate. The achievable draw ratio of each film sample drawn at a constant rate and a temperature near T_op is referred to as the D_raop, which reached another maximum value as the drawing rates approached an optimum value. Dynamic mechanical analysis of the film sample exhibited an extraordinary high transition peaked at temperature near 95°C, which is again very close to the T_op value found for the film sample drawn at a relatively low rate. On the other hand, the birefringence values and tensile strengths of the film specimen were found to improve significantly with the draw ratios, although the improvement of these properties reduced significantly at high draw ratios. Moreover, both the drawing temperature and rate showed beneficial influence on the birefringence, and tensile strengths of the drawn film specimens. Possible mechanisms accounting for these interesting deformation properties are suggested.     

UHMWPE/CNTs复合纤维的结晶行为研究

分别用DSC、X衍射、热台偏光显微镜对超高分子质量聚乙烯（UHMWPE）和UHMWPE／CNTs（碳纳米管）复合纤维的结晶行为进行了研究。结果表明：碳纳米管的加入使得复合材料的熔点较UHMWPE有所提高,碳纳米管起到了成核剂的作用。晶片厚度较UHMWPE增加。     

超高分子量聚乙烯的研究现状

介绍了超高分子量聚乙烯（UHMWPE)的性能，用途和工艺特点以及国内外关于流动改性UHMWPE的研究现状，阐述了共混改性、润滑剂改性和液晶高分子原位复合材料改性三种加工性能改性方法。     

Shrinkage analysis of forged ultra-high molecular weight polyethylene parts

Some engineering thermoplastics cannot be easily processed by injection molding because of their high viscosity. This is the case for Ultra-High Molecular Weight Polyethylene (UHMWPE). Parts are either compression molded or machined from extruded shapes. Over the years, forging has been increasingly used to produce more or less complicated parts. Forging is a process in which a preform is subjected to bulk deformation in constraining dies, by applying heat and pressure, but with the polymer remaining in the solid (semi-crystalline) phase. To fabricate acceptable mechanical components such as gears and sprockets, a close control of the operating conditions and a good prediction of shrinkage are necessary, For a better understanding, a study has been conducted on forged UHMWPE disks and gears. Parameters such as material and mold temperatures, dwell time, speed of forging and dwell pressure were investigated. Results show that material and mold temperatures are the most important parameters. For gears, optimization of processing conditions led to a shrinkage of ～0.2 percent, measured on pitch diameter. The effect of post-annealing at various temperatures is also reported.     

Annealing of gel-spun hot-drawn ultra-high molecular weight polyethylene fibres

Summary Gel-spun hot-drawn ultra-high molecular weight polyethylene (UHMWPE) fibres were annealed with fixed fibre ends, at temperatures near the orthorhombic-hexagonal lattice transition temperature. A permanently reduced tensile modulus without loss in tensile strength, i.e. increased elongation at break, was observed upon tensile testing of these annealed fibres. The uncharged tensile strength upon annealing, indicates that the tensile strength is likely to be determined by the entanglement concentration.     

纤维增强超高分子量聚乙烯的研究进展

介绍了超高分子量聚乙烯(UHMWPE)的优缺点和改性方法。从复合材料制备和增强效果两方面重点综述了纤维增强UHMWPE的改性研究现状,并对其未来的研究方向进行了展望。     

The breaking strength of ultra-high molecular weight polyethylene fibers

Ultimate mechanical properties of polyethylene fibers were measured. Results are in close agreement with the stress-induced melting theory of fracture (for finite molecular weight polymers). The perfect fiber work of rupture W_c, modulus K_c, strength σ_c, and strain _c are found to be W_c=0.084±0.003 GPa; σ_c=7.5 GPa; K_c=335±12 GPa; _c=0.0225±0.0005. The activation energy of fracture is measured as ≈108 kJ/mol—the activation energy of polyethylene fusion and one-third the activation energy of bond scission. Non-uniformity of fibers necessitates averaging properties over several test lengths. Actual stress-strain curves are decomposed into thermodynamic and irreversible components. Fusion theory applies to the thermodynamic component..     

The adhesive properties of chlorinated ultra-high molecular weight polyethylene

Ultra-high molecular weight polyethylene (UHMW-PE) is well known for its abrasion and chemical resistance. Recently we developed a new application for UHMW-PE as a liner in elastomeric hoses. It was found that the adhesion between UHMW-PE and elastomers such as ethylene-propylene-diene monomer (EPDM) and styrene-butadiene rubber (SBR) is sufficient for practical applications, but the adhesion to nitrile rubber (NBR) is poor. In order to improve the adhesion between NBR and the UHMW-PE liner, (nascent) powder chlorinated polyethylenes were used as interlayers between UHMW-PE and NBR. These powder chlorinated polyethylenes are polymers with a dual nature and are composed of highly chlorinated polyethylene segments compatible with NBR and polyethylene segments compatible with UHMW-PE. In order to achieve sufficient adhesion, the chlorine content of the chlorinated blocks should be at least 15 wt%. If these powder chlorinated UHMW-PEs have a chlorine content of 15 wt% in the chlorinated blocks, dilution with polyethylene hardly affects the adhesive properties, which is an advantage in the practical use of these materials as interlayers.     

超高相对分子质量聚乙烯纤维改性方法

简介了超高相对分子质量聚乙烯纤维的性能与应用,重点阐述了低温等离子处理法、辐照接枝改性法、化学氧化法和电晕放电法4种常用的对超高相对分子质量聚乙烯纤维改性方法的研究情况。综述表明,无论采用以上任何一种改性方法,都能相应有效改善纤维的表面性能,提高纤维与其它材质间的粘接性。     

超高相对分子质量聚乙烯纤维的改性及其应用

超高相对分子质量聚乙烯（UHMWPE）纤维以其优异的性能而成为一种重要的高科技纤维品种,但由于本身的结构特点,使得其存在一定的性能缺陷而限制了应用范围。通过等离子体处理法、氧化法等各种物理和化学的方法对UHMWPE纤维表面进行改性处理,可不同程度改善其耐热、界面、抗蠕变等弱性。详细介绍了该纤维的改性方法及其在绳索类、防护用品以及其他方面的应用。     

UHMWPE/LLDPE/HBP共混体系流变行为研究

为改善超高相对分子质量聚乙烯(UHMWPE)的加工流变性,将超支化聚酯酰胺(HBP)和线性低密度聚乙烯(LLDPE)与UHMWPE共混,研究了不同比例UHMWPE/LLDPE/HBP共混体系的流变行为。结果表明:UHMWPE/LLDPE/HBP共混体系熔体表观粘度随HBP质量分数的增加而减小;共混体系非牛顿指数<1,为典型的切力变稀流体;当剪切速率为10 s-1时,共混体系的粘流活化能较小;结构粘度指数随HBP质量分数增加而下降,随UHMWPE粘均相对分子质量增加而增大。     

UHMWPE/CNTs冻胶体系的流变行为研究

研究了碳纳米管(CNTs)的加入对超高分子质量聚乙烯(UHMWPE)稳态表观粘度、粘流活化能、非牛顿指数和结构粘度指数的影响。结果表明:碳纳米管添加量小于或等于3ω时,UHMWPE/CNTs冻胶体系的粘流括化能降低,表观粘度都低于空白UHMWPE冻胶体系。CNTs的加入对UHMWPE冻胶体系的非牛顿指数和结构粘度指数影响不大。