Experimental and theoretical analysis of failure mechanism of UHMWPE Yarn under transverse cut loading

This paper is concerned with transverse cut resistant properties of UHMWPE yarns by the methods of experimental and theoretical analysis. Rheological theory of fabric was applied to evaluate relation of stress and strain of UHMWPE yarn, when the UHMWPE yarn is subjected to external cut force. The dynamic response of yarn and the contact volume of yarn and blade in the cutting have been identified to interpret cut failure mechanism of yarn. The experimental results show that yarn structure, blade edge, and test parameters have great influence on cut resistant property of UHMWPE yarn, and which are consistent with the theoretical analysis. It provides a theoretical basis for quantifying the cutting resistance of fabrics.     

UHMWPE/HDPE/纳米SiO2共混体系的毛细管挤出流变行为

采用毛细管流变仪,研究了超高分子量聚乙烯(UHMWPE)/高密度聚乙烯(HDPE)/纳米二氧化硅(SiO2)共混体系,及其对照组的流变行为和挤出过程中的不稳定流动现象,分析了共混物发生鲨鱼皮畸变和整体破裂的临界剪切应力和临界剪切速率的变化情况。结果表明,经过偶联剂改性的纳米SiO2粒子,在PE基质的共混体系中存在一定的界面黏附作用,降低了纳米共混体系的挤出胀大比,弹性特征减轻。这种界面相互作用限制了纳米共混材料在口模区域的黏性流动以及分子链离开口模后的构象恢复,降低了发生流动不稳定现象的临界剪切速率,发生鲨鱼皮畸变的临界剪切应力增大,整体破裂后,形成交替出现"鲨鱼皮-破裂"的振荡性变化外观。     

超高分子量聚乙烯成型工艺及其加工设备研究进展

综述了超高分子量聚乙烯(UHMWPE)的熔体特性与加工性能,介绍了模压成型、挤出成型和注塑成型等主要成型方法和加工工艺,并简述了UHMWPE专用加工设备的应用和发展情况;最后展望了UHMWPE的应用前景.     

An energy-based model for the wear of UHMWPE

An energetic approach to model the wear of tribological systems in which one of the components of the pair is polymeric is presented in this work. Experimental data, obtained in ultra-high molecular weight polyethylene (UHMWPE) pin-on-disk tribological tests, showed that a linear correlation between the wear rate of the polymer and the dissipated energy exists, independently of the lubricant, of the material used as counterbody and of the surface finishing of both polymer and counterbody. This fact strongly suggests that, in UHMWPE-based tribological systems, energy dissipation is mainly caused by the elasto-plastic deformation and wear of the polymer. Based on this assumption, it is developed a mathematical model that yields for a physical interpretation of the parameters of the experimental wear vs. energy correlation. These parameters are intrinsic wear properties of the polymer and can be used for the optimization of polymer-based tribological systems.     

Ku/Ka双频段防弹天线罩复合材料性能

为解决Ku/Ka双频段天线罩的防弹和透波问题,本文通过波导法研究材料的介电性能,并利用HFSS软件对双频工作的复合材料进行透波性能仿真设计,并采用试验与理论计算验证了超高分子量聚乙烯（UHMWPE）防弹和透波性能。研究表明：UHMWPE的介电性能优异,适用于Ku/Ka双频段天线罩。HFSS仿真设计表明,7 mm UHMWPE的Ku频段损耗为0.2 dB,Ka频段损耗为0.6 dB,仿真结果与实际测试结果吻合。防弹打靶试验表明,面密度为5.6 kg/m²的UHMWPE防弹等级优于1级,实测V₅₀值为546 m/s。     

UHMWPE初生态微观结构及不同成型条件下制品力学性能研究

超高分子量聚乙烯(UHMWPE)极高的分子量及线性分子链特性使其具备很多的优异性能,在军工、医药卫生等领域的应用越来越广泛的同时,对UHMWPE树脂的性能不断提出更高的要求。故利用高分辨扫描电镜(SEM)、高温凝胶色谱-红外联用(GPC-IR)、拉曼光谱(Raman)及差式扫描量热仪(DSC)对树脂初生态粒子的结晶结构、分子特性及热力学性能进行了研究,并通过控制模压过程中的冷却速率来研究UHMWPE样品的结晶行为,进而分析UHMWPE微观特性与宏观性能之间的关系。研究发现由次级颗粒和微纤组成的UHMWPE初生态粒子中具有大量的片晶和伸直链,分子链排列规整,结晶度高;但在熔融再结晶加工成制品的过程中,分子链的规整性遭到破坏,与初生态粒子相比,结晶度下降、缠结密度变大。另外,不同降温速率的样品中淬冷样品的分子链缠结密度最低,而低缠结、小的晶粒能够提升制品的耐冲击性能及断裂时的真应力。     

高分子润滑剂对PBTP摩擦磨损性能的影响

探讨了ＰＴＦＥ、ＵＭＷＰＥ对ＰＢＴＰ摩擦、磨损性能的影响。结果表明，添加５％和ＵＨＭＷＰＥ或ＰＴＦＥ的ＰＢＴＰ与纯ＰＢＴＰ相比，摩擦因数大幅度降低；ＰＶ值明显提高，可分别为ＰＢＴＰ的２．４倍和１．６倍；耐磨损性较为ＰＢＴＰ提高约２０倍和３０倍     

Solvents effect in horseradish peroxidase catalyzed modification of UHMWPE fiber

Graft copolymerization of acrylamide onto ultrahigh molecular weight polyethylene (UHMWPE) using horseradish peroxidase as catalyst was performed in different reaction solution to study the solvent effect. The factors affecting the grafting effect such as the solvents composition, initiator, reaction temperature, and reaction time were investigated. The grafted UHMWPE fiber surface was characterized by IR spectrum, scanning electron microscopy, thermal analysis, contact angle measurement, and single fiber pull out test. Polar groups such as ? CO and ? NH₂ are approved to appear on the surface after treatment. The contact angle with water decreased from 85 to 50, indicating the wettability of the fiber has been increased. The surface of the grafted fiber became rougher and its adhesion to resin increased significantly, and hence is expected to produce reinforced plastics with resin. It was also found that the grafting effect was higher in dioxane than in other solvents used and the initiator substituted by electron donating group facilitates the grafting reaction. And the optimum reaction condition was determined to be reacting in 40% (v/v) dioxane solution at 30°C for 2 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 674–678, 2006     

Structural Evolution of UHMWPE Fibers during Prestretching Far and Near Melting Temperature: An In Situ Synchrotron Radiation Small‐ and Wide‐Angle X‐Ray Scattering Study

Combining a homemade extension apparatus and the in situ synchrotron radiation small‐ and wide‐angle X‐ray scattering methods for measurement, the structural evolutions of gel‐spun ultrahigh molecular weight polyethylene (UHMWPE) fibers during prestretching at temperatures of 25 and 100 °C are investigated, respectively. Lamellar rotation toward the stretching direction occurs before strain hardening, while the folded‐chain crystal destruction and extended‐chain fibril formation processes occur in the strain hardening zone at 25 °C. While at 100 °C, stretching induced crystal melting before the stress plateau region and formation of fibrous crystals at the onset of the stress plateau are observed. Further stretching results in shear displacement of crystal blocks and, finally, destruction of the folded‐chain crystals and formation of extended‐chain fibrils. Prestretching UHMWPE fibers at 100 °C within a certain strain range can produce highly oriented fibrous crystals, which may provide an ideal precursor structure for the poststretching process.     

低温等离子体处理UHMWPE纤维表面性能的多指标优化

利用正交表安排试验,对超高相对分子质量聚乙烯(UHMWPE)纤维进行空气低温等离子体处理,测试各处理条件下UHMWPE纤维的力学和表面摩擦性能;采用矩阵分析法对多指标正交试验结果进行优化分析,找出最优方案并进行黏着性试验验证。结果表明:经空气低温等离子体处理后,UHMWPE纤维的断裂强度有所减小,表面静、动摩擦因数有较大幅度的提高;处理纤维的最优方案为功率50 W、压强15 Pa、时间150 s,此时纤维的断裂强度损失率仅为2.53%,剥离功为未处理时的4.25倍,说明由矩阵分析法得出的最优方案在保证纤维断裂强度损失很小的情况下,黏着性得到了很大程度的改善。