Friction and wear properties of ultra-high molecular mass polyethylene reinforced with Al2O3 nano-particle

The ultra-high molecular mass polyethylene (UHMMPE) as an artificial joint acetabular material was filled with nano-powder of Al2O3 of various mass fractions. The effect of Al2O3 mass fraction on the hardness, wetting property and tribological properties of the Al2O3-UHMMPE composites under dry friction sliding against both stainless steel and Ti-6Al-4V alloy was investigated. The morphologies of the worn surfaces of composites were observed with optical microscope. The results show that, wetting property and wear resistance of the composites are improved by filling Al2O3, while the friction coefficient is decreased largely under dry friction as compared with that of the unfilled UHMMPE. This is attributed to the reinforcing function of the nano-powder of Al2O3 in the composites. The wear of UHMMPE is dominated by plowing, plastic deformation and fatigue wear; while the Al2O3-UHMMPE composites are characterized by the mild fatigue wear.

Ultra-High Molecular Weight Polyethylene Tape Applied for Distal Humeral Condyle Fracture around Total Elbow Arthroplasty in Patients with Rheumatoid Arthritis: Report of Two Cases

Managing fractures of distal humerus in patients with rheumatoid arthritis (RA) is technically challenging. Total elbow arthroplasty (TEA) is one of the treatment options for these fractures. While elbow motion is largely regained by TEA, comminuted condyle fragments are often ignored. Although numerous approaches for repair of condylar fragments around TEA are described, any universal fixation strategy for these fractures has not been established. This report describes, for the first time, application of an ultra-high molecular weight polyethylene (UHMWPE) tape for the treatment of distal humerus fracture in 2 patients with rheumatic elbow arthropathy. The post-operative clinical courses were good. Radiographs showed bony union of the condylar fragments without loosening in two cases. Because of its flat configuration, softness, and flexibility, UHMWPE tape is a promising material for stabilizing fracture of the distal humerus associated with TEA.

Temperature Effect on the Conformation Transition of Ultra-high Molecular Weight Polyethylene/Polypropylene Blends Undergoing Continuous Volume Extensional Flow:A Mesoscopic Simulation

Due to the multiformity and complexity of chain conformation under external flow and the challenge of systematically investigating the transient conformation and dynamic evolution process of polymer chains at the molecular level by means of present experimental techniques,a universal description of both chain conformation and dynamics with respect to continuous volume extensional flow(CVEF)is still absent.Taking into account the temperature effect,we performed dissipative particle dynamics(DPD)simulations with the particles corresponding to the repeat units of polymers over a wide temperature range and analyzed the correlation with the conformational properties of ultra-high molecular weight polyethylene/polypropylene(UHMWPE/PP)blend in response to the CVEF.With time evolution,the polymer chains become highly oriented parallel to the flow direction instead of the initial random coiling and self-aggregation.It is found that a high temperature is necessary for more substantial compactness to take place than low temperature.The low-k plateau and low-k peak in structure factor S(k)curves suggest a low degree of conformational diversity and a high degree of chain stretching.It is also concluded that the intra-molecular C-C bond interaction is the main driving force for the dynamics process of the chain conformations undergoing CVEF,where the motion of the alkyl chains is seriously restricted owing to the increase in bond interaction potential,resulting in a reduction of the difference in diffusion rates among alkyl chains.

Cyclic Pulsating Pressure Enhanced Segregating Structuration of Ultra-High Molecular Weight Polyethylene/Graphene Composites as High-performance Light-Weight EMI Shields

Currently,the enhancement in electromagnetic interference(EMI)performance of polymeric composite generally relies on either improving electrical conductivity(σ)for stronger electromagnetic(EM)reflections or tailoring structure for higher EM resonances.Herein,we proposed a novel technique called cyclic pulsating pressure enhanced segregating structuration(CPP-SS),which can reinforce these two factors simultaneously.The structural information was supplied by optical microscopy(OM)and scanning electron microscopy(SEM),both of which confirmed the formation and evolution of segregate structured ultra-high molecular weight polyethylene(UHMWPE)/graphene composites.Then,the result showed that CPP-SS can significantly improve theσof samples.Ultimately,advanced specific EMI shielding efficiency of 31.1 d B/mm was achieved for UHMWPE/graphene composite at 1-mm thickness and a low graphene loading of 5 wt%.Meanwhile,it also confirmed that the intrinsic disadvantage of poor mechanical properties of conventional segregated structure composites can be surpassed.This work is believed to provide a fundamental understanding of the structural and performance evolutions of segregated structured composites prepared under CPPSS,and to bring us a simple and efficient approach for fabricating high-performance,strong and light-weight polymeric EMI shields.

PREPARATION AND CHARACTERIZATION OF ULTRA-HIGH MOLECULAR WEIGHT POLY(ETHYLENE TEREPHTHALATE)(PET)FIBER

This paper reports the spinning and drawing behavior of Ultra-high Molecular Weight polyethylene Terephthalate) (UHMW-PET) fibers. The as-spun fibers were produced by dry-jet wet spinning of a 15%-17% solution in 50:50(v:v) trifluroroacetic acid and dichloromethane. Both molecular weight and polymer solution concentration have marked effect on the drawability of the as-spun-fibers. The maximum extension drawing ratio (EDRmax) of as-spun fiber increases with increasing molecular weight, whereas optimal concentration to achieve the EDRmax of as-spun fibers decreases with increasing molecular weight. Drawing speed and temperature during the first step have remarkable effect on the drawability of these fiber during the second step. Relatively lower drawing temperature and drawing speed (19 ℃ , 60 mm/min) during the first drawing step was beneficial to mechanical properties of ultimate fibers. At the range of 210 ℃ to 230 ℃, the draw ratio (DR) during the second step increases with increasing temperature.

Progressive Failure Analysis of Quasi-isotropic Self-reinforced Polyethylene Composites by Comparing Unsupervised and Supervised Classifications of Acoustic Emission Data

Unsupervised and supervised pattern recognition( PR)techniques are used to classify the acoustic emission( AE) data originating from the quasi-isotropic self-reinforced polyethylene composites,in order to identify the various mechanisms in the multiangle-ply thermoplastic composites. Ultra-high molecular weight polyethylene / low density polyethylene( UHMWPE / LDPE)composites were made and tested under quasi-static tensile load. The failure process was monitored by the AE technique. The collected AE signals were classified by unsupervised and supervised PR techniques, respectively. AE signals were clustered with unsupervised PR scheme automatically and mathematically. While in the supervised PR scheme,the labeled AE data from simple lay-up UHMWPE / LDPE laminates were utilized as the reference data.Comparison was drawn according to the analytical results. Fracture surfaces of the UHMWPE / LDPE specimens were observed by a scanning electron microscope( SEM) for some physical support. By combining both classification results with the observation results,correlations were established between the AE signal classes and their originating damage modes. The comparison between the two classifying schemes showed a good agreement in the main damage modes and their failure process. It indicates both PR techniques are powerful for the complicated thermoplastic composites. Supervised PR scheme can lead to a more precise classification in that a suitable reference data set is input.

聚乙烯相对分子质量及其分布快速评价方法研究

以国内外采用不同工艺和催化剂生产的17种聚乙烯的测试结果为基础,通过理论推导与模型拟合相结合,建立了以熔体流动速率快速计算相对分子质量及其分布的方法,并由此计算出数均分子量。经验证,该方法准确性较好,可弥补凝胶渗透色谱法的不足,有利于装置生产过程中准确控制产品质量和提高新产品开发效率。

聚乙烯纤维在混凝土中的应用研究进展

综述了超高相对分子质量聚乙烯纤维及其他聚乙烯纤维对混凝土性能的影响,以及在混凝土开发中的应用研究进展。聚乙烯纤维的桥接作用可阻止混凝土裂纹的产生及扩展,提高混凝土的力学性能和耐腐蚀性能,一方面为聚乙烯纤维在建筑领域的应用提供了可能,另一方面也为超高性能混凝土的开发提供了机遇。应加强聚乙烯纤维增强混凝土的系列化、标准化研究,尽快实现工业化。

低缠结超高相对分子质量聚乙烯的制备及表征

为解决传统Ziegler-Natta催化剂(简称Z-N催化剂)制备的超高相对分子质量聚乙烯(UHMWPE)缠结程度较高、加工困难等问题,以MgCl_(2)、TiCl_(4)、异辛醇、正硅酸四乙酯(或邻苯二甲酸二己酯)为主要原料,采用化学反应法制备了氯化镁负载型Z-N催化剂cat1(或cat2)。分别以cat1、cat2为主催化剂、三乙基铝为助催化剂,采用淤浆聚合工艺制备了低缠结UHMWPE,测定了cat1、cat2的粒径分布和金属元素质量分数,考察了聚合温度、时间对催化剂催化活性和UHMWPE的黏均相对分子质量(M_(v))的影响,并使用流变分析法和DSC热力学退火法对UHMWPE的缠结程度进行了表征。结果表明,制备的cat1、cat2与设计相符,在聚合反应温度分别为65和70℃、反应5 h时,cat1、cat2催化活性分别达到27700、37700 g PE/g cat,制备的UHMWPE的Mv分别为6.01×10^(6)、5.03×10^(6),起始储能模量分别为0.21、0.13 MPa,缠结程度低于商品化UHMWPE。

淤浆法聚乙烯装置反应釜中产物的特性

在中国石油兰州石化公司17万t/a高密度聚乙烯装置上,采用三釜串联淤浆法生产工艺生产聚乙烯,利用扫描电子显微镜、凝胶色谱仪、差示扫描量热仪等表征方法,考察了3台反应釜中产物的粒径分布、相对分子质量分布、熔融-结晶性能等特性。结果表明:3台反应釜中产物的组分均呈不规则颗粒状,相对分子质量分布曲线均为单峰;第2、第3反应釜中的产物粒径分布趋于集中,相对分子质量分布较宽;第1、第2、第3反应釜中产物的熔融曲线和结晶曲线均只有1个峰,共聚单体的引入会降低共聚物的结晶能力。

用结晶度表征UHMWPE相对分子质量研究

利用差示扫描量热仪和乌式黏度计研究了超高相对分子质量聚乙烯(UHMWPE)结晶度与相对分子质量的关系。结果表明:UHMWPE相对分子质量越大,结晶度越低,UHMWPE结晶度和相对分子质量呈现近似线性关系。拓展到低相对分子质量部分以后,聚乙烯(PE)结晶度和相对分子质量偏离了线性关系,相对分子质量对结晶度的影响更为明显。建立了UHMWPE结晶度和相对分子质量的拟合公式。

EVA装置生产的LDPE结构与加工性能研究

分析了乙烯-醋酸乙烯共聚物(EVA)装置上生产的低密度聚乙烯(LDPE)A与市售同类料LDPE B的差异,指出EVA装置因装置保护带来聚合工艺的差异,长、短支链支化作用降低,链段拓扑结构及立构规整性的差异可能是LDPE A熔体流动速率、密度等宏观物性偏低的主要原因;其短支链多、分子链均方回转半径小可能是LDPE A相对分子质量、结晶度等微观物性偏低的主要原因。EVA装置因三峰运行生产的LDPE A与同类料LDPE B相比,薄膜制品光学性能优,摩擦系数低,拉伸性能、加工流变性能、熔融温度相当,即聚合工艺的调整未对制品性能产生负面影响。

锂电池隔膜用聚乙烯的结构与性能

采用高温凝胶渗透色谱仪、熔体流动速率仪、堆积密度计和扫描电子显微镜等对国内外几种锂电池隔膜用聚乙烯(PE)的相对分子质量、熔体流动速率、堆密度和形貌等进行了分析和表征,并采用PE/白油溶胀的方法研究了其溶胀性能。结果表明:试样B4的粒径集中在75~150μm,堆密度最高为0.50 g/cm^(3),熔体流动速率为0.01 g/10 min,相对分子质量分布为4.17,形态规整,溶胀效果最好,更紧实,最适用于制备锂电池隔膜。由此表明:适用于生产锂电池隔膜的PE具有颗粒分布均匀、形态规整、相对分子质量分布窄、溶胀性能好等特点。

Dissolving of Ultra‑high Molecular Weight Polyethylene Assisted Through Supercritical Carbon Dioxide to Enhance the Mechanical Properties of Fibers

The molecular weight of ultra-high molecular weight polyethylene(UHMWPE)fbers is severely decreased compared with raw materials due to high temperature and strong shearing in the dissolving process.In this study,we reported a novel method to assist the dissolving of UHMWPE in parafn oil without severe degradation in order to improve the tensile strength of resultant fbers.UHMWPE fbers with relatively high molecular weight and more excellent disentanglement efect were prepared by gel-spinning with UHMWPE suspension treated with supercritical carbon dioxide(SC-CO_(2)).The dynamic thermomechanical,mechanical and crystalline properties of UHMWPE extracted fbers and drawn fbers were researched comprehensively.UHMWPE extracted fbers obtained after SC-CO_(2) treatment display a higher molecular weight.More importantly,it is clear that the disentanglement of UHMWPE gel fbers gained by processing SC-CO_(2) has been signifcantly promoted compared with that without SC-CO_(2) treatment from dynamic thermomechanical and rheological results,which could also be demonstrated from the cross-sectional morphology of UHMWPE extracted fbers.Furthermore,the tensile strength of UHMWPE fbers prepared through SC-CO_(2) treating is able to attain 30.11 cN/dtex,increased by 10.3%in comparison to UHMWPE fbers gained without assistance of SC-CO_(2).Beyond that,the thermal behavior and crystallization performance of UHMWPE extracted fbers and drawn fbers acquired by way of SC-CO_(2) treatment have also been enhanced.

Analysis of Pharmacodynamic Substance Basis of Fufang Changtai in Treating Colorectal Cancer by UPLC-Q-TOF-MS Combined with Network Pharmacology

[Objectives] To systematically study the main active components of Fufang Changtai(FFCT) in the treatment of colorectal cancer(CRC), and to explore its mechanism of action. [Methods] The main chemical components of FFCT were analyzed by ultra-high performance liquid chromatography with quadrupole time-of-flight mass spectrometry(UPLC-Q-TOF-MS) combined with automatic analysis platform, and the main pharmacodynamic substances of FFCT were studied by network pharmacology method and its mechanism of action was explored. The binding degree between the active components and the core targets were verified by molecular docking technology. [Results] A total of 86 compounds were identified from FFCT, among which 26 compounds were Ginsenoside Rg3, Ginsenoside Rb1, Astragaloside III, etc. The key target pathway enrichment analysis showed that FFCT played its role in the treatment of CRC mainly through the PI3K-Akt signaling pathway and MAPK signaling pathway. [Conclusions] This study comprehensively identified the FFCT components. Supplemented by network pharmacology and molecular docking technology, it is expected to provide a scientific theoretical basis and an important reference for FFCT therapeutic components identification, key target verification and mechanism of action in the treatment of CRC.

纤维级超高相对分子质量聚乙烯树脂开发

在中国石油辽阳石化公司8万t/a Hoechst淤浆法高密度聚乙烯装置上,采用自主研发的LHPEC-3催化剂,开发出纤维级超高相对分子质量聚乙烯树脂(UHMWPE,牌号为FIUH 4000)。结果表明:在小试聚合评价实验中,催化剂LHPEC-3的活性为3.2×10^(4)g/g,制备的UHMWPE树脂黏均相对分子质量在350×10^(4)g/mol以上;在中试聚合试验中,催化剂LHPEC-3的活性为3.6×10^(4)g/g,产品FIUH 4000黏均相对分子质量在400×10^(4)g/mol以上,堆密度达到0.43 g/cm^(3),力学性能良好;在工业化试生产中,产品FIUH 4000颗粒分布在110~300μm,分布指数为0.836,适用于纺丝加工应用。

钛系催化剂对PE 100管材专用树脂性能的影响

在中韩(武汉)石油化工有限公司30万t/a高密度聚乙烯(PE)装置上,分别采用2种钛系催化剂(进口Avant Z系列催化剂、国产BCE-H 100催化剂)生产出PE 100级管材专用树脂,对2种专用树脂的粒径尺寸、相对分子质量及其分布、力学性能等进行了对比。结果表明:与进口催化剂生产的PE管材粉料相比,国产催化剂生产的粉料粒径分布更多地集中在200~500μm,平均粒径为235.6μm,细粉含量更低,高分子链段中的共聚单体含量低,简支梁缺口冲击强度低,拉伸屈服应力、弯曲模量、拉伸断裂应变、氧化诱导时间相当;国产催化剂生产的PE管材料相对分子质量分布指数为32.53,比进口催化剂生产的PE树脂宽;2种管材料生产的管材均可通过100,165,1000 h静液压测试。

Micro-Macro Scale Relationship in Creep Deformation of Ultra High Molecular Weight Polyethylene

Macroscopic and microscale creep deformations of UHMWPE were investigated by using in situ SAXS.A methodology for the measurement of the local creep deformation of inter-lamellar amorphous phase has been proposed.The local strain of inter-lamellar amorphous phase(£a)and macroscopic strain(£macro)were evaluated and they were compared to study the relati on ship betwee n macroscopic and microscale creep deformation of UHMWPE.Both of them exhibit two deformation regions against creep time.The entanglements show a strong impact on both the macroscopic and local inter-lamellar amorphous phase creep behavior and they can be well correlated to the molecular weight between two entanglements estimated from strain-hardening modulus.Compared to the macroscopic creep deformation,local inter-lamellar amorphous layers have a smaller creep deformation.From the local creep measurement,the apparent modulus of inter-lamellar amorphous phase can also be estimated(200<Ma<500 MPa).These values are much higher than the Young's modulus of bulk amorphous PE,which can be well explained by the confinement of the lamellar stacks and the enhancement of the amorphous phase with the relatively high concentration of entanglements.This study provides a useful means and quantitative data for achieving the scale transition between the micro and the macro structural levels for the study of viscos-elastic deformation.

聚乙烯的动态流变行为分析

采用动态流变测试研究了角频率、黏度、储能模量、损耗模量、损耗因子等的变化规律,并讨论了它们与聚乙烯分子结构的关系。结果表明:交点模量(G_x)对应的频率越低,聚乙烯的重均分子量越大;G_x的纵向位置越低,聚乙烯的相对分子质量分布越宽;宽分布可以使聚乙烯剪切变稀行为更加明显,但不能排除长支链的影响;通过动态黏度-虚数黏度曲线和损耗因子随角频率的变化可以判断树脂结构中是否含有长支链。

冷冻升华制备的超高分子量聚乙烯寡链、多链晶体的凝聚态

在 1 0 - 3～ 1 0 - 5g/ m L浓度范围内 ,用冷冻升华法制备了超高分子量聚乙烯 (UHPE)单链、寡链、多链的折叠链晶聚集体 .长达几万纳米的 UHPE分子链可以以不同的片晶参与结晶 ,或自身形成数个晶粒 ,即形成单链多晶 .DSC研究结果表明 ,随着溶液浓度的降低 ,冷冻升华样品的熔点和结晶度均降低 .由熔点估算了晶粒的体积和晶粒中包含的链数 ,它们亦随溶液浓度降低而降低 .冷冻升华得到的小晶粒中链的缠结少 ,晶体具有较高的完善性 .用 WAXD测试晶粒的 (1 1 0 )和 (2 0 0 )面的法向尺寸 ,由此计算晶粒的平均体积 。