超高分子量聚乙烯人工髋臼材料压缩性能的红外辐射研究

采用先进的试验设备和方法对超高分子量聚乙烯(UHMW PE)人工髋臼材料在不同的加载速度下进行压缩力学性能试验的同时,对其压缩变形过程进行了热红外辐射温度的监测。对超高分子量聚乙烯人工髋臼材料试验过程中的应力与应变、平均红外辐射温度与应变、平均红外辐射温度与机械功之间的关系进行了分析。试验结果为超高分子量聚乙烯人工髋臼材料在特殊的人体环境中的应用提供了参考。     

超高分子量聚乙烯纤维表面改性及其界面性能研究进展

超高分子量聚乙烯(UHMWPE)纤维因具有高化学稳定性,高机械性能和低成本等优点而成为理想增强材料之一。然而,规整的非极性分子链结构致使UHMWPE纤维结晶度高、与树脂基体之间几乎无化学键合,本文因而与树脂的粘合性差。为此已经进行了许多纤维表面处理的工作,如紫外辐射、等离子体处理、聚合物涂层等。主要从湿法化学改性和干法化学改性这两方面入手,总结归纳了目前超高分子量聚乙烯纤维的界面改性研究现状,从物理和化学两个方面揭示界面增强机理以及界面性能与复合材料力学性能的关系,为超高分子量聚乙烯纤维的界面结构设计和改性提供科学理论依据和技术指导。     

超高分子量聚乙烯/石墨烯纳米复合材料的制备及其热性能的研究

为了提高超高分子量聚乙烯的热性能,本文通过溶液共混的方法利用氧化石墨烯改性不同分子量的超高分子量聚乙烯,然后利用红外测试(FTIR)、X射线衍射测试(XRD)、扫描电镜测试(SEM)、差热扫描量热分析仪(DSC)和热失重分析(TG)的方法对超高分子量聚乙烯/石墨烯纳米复合材料的结构、表面形态和性能进行了研究.通过分析测试表明氧化石墨烯在超高分子量聚乙烯/石墨烯纳米复合材料中的分散性良好,氧化石墨烯的添加量为0.3%时,石墨烯/超高分子量聚乙烯的复合材料的热稳定性等性能最好,与原材料相比提高了3℃.     

超声场致作用对UHMWPE流变及拉伸性能的影响

利用本实验室自行研制的超声混炼装置对超高分子量聚乙烯(UHMWPE)进行超声混炼,通过实验发现,超声混炼可有效地降低UHMWPE的粘度。并且不会使其力学性能有很大降低,甚至由于超声场致作用使得材料的断裂伸长率等性能得到很大提高。     

超高分子量聚乙烯摩擦学性能研究进展

综述了超高分子量聚乙烯(UHMWPE)在摩擦学领域的研究进展,着重评述了UHMWPE材料在人工关节方面的应用以及在减摩耐磨材料方面的研究,并提出了UHMWPE作为减摩耐磨材料在研究与应用方面几个亟待解决的问题.     

超高分子量聚乙烯的熔融缺陷

针对超高分子量聚乙烯(UHMWPE)成型加工中存在的熔融缺陷问题,通过在不同加工条件下对超高分子量聚乙烯进行模压成型,研究熔融缺陷的形成及对制品力学性能的影响。采用对制品进行扫描电镜(SEM)断面形貌观察、力学拉伸和差示扫描量热(DSC)测试,结果发现,延长加工时间或提高加工温度,UHMWPE的结晶行为无明显变化,但都能够有效地改善超高分子量聚乙烯的熔融缺陷,能提高制品的断裂强度和断裂韧性等力学性能。     

超高分子量聚乙烯纤维在防弹材料上的应用

本文就超高分子量聚乙烯纤维作为一种防弹材料 ,综述了其性能特点及在防弹材料上的应用     

不锈钢表面粗糙度对超高分子量聚乙烯摩擦磨损性能的影响

以超高分子量聚乙烯软骨材料为销样,316不锈钢硬骨材料为盘样,在自制的销－盘式磨损试验机上考察了不锈钢盘样表面粗糙度对超高分子量聚乙烯摩擦磨损性能的影响,并利用光学显微镜观察了摩擦副表面的形貌,结果表明,在干摩擦条件下,表面粗糙度对超高分子量聚乙烯的摩擦磨损有较大影响,存在着适合的表面粗糙度范围,使超高分子量聚乙烯摩擦系数,磨损率最小。     

日本开发超高分子量聚乙烯纤维制造方法

几年前荷兰发表了适用于超高分子量聚乙烯的稀薄溶液的凝胶超高拉伸法,该法不仅可通过高取向化使纤维达到极限性能而受到高度的重视,而且由于提出了用聚乙烯作原料制取高强度高弹性纤维的可能性而受到注目。用齐格勒法制取的分子量超过一百万的超高分子量聚乙烯,由于许多分子形成复杂的络合结构,所以具有其他塑料所不具备的耐磨耗性、耐冲击性和耐应力龟裂性等特性。这种复杂的络合物分子若以一定的方     

萃取剂对UHMWPE微孔膜结构与性能的影响

采用热致相分离(TIPS)法制备超高分子量聚乙烯(UHMWPE)微孔膜,研究了分别以正己烷、乙醇和1,2-二氯乙烷作为萃取剂对超高分子量聚乙烯微孔膜结构及其性能的影响.实验表明,当萃取剂依次是正己烷、乙醇和1,2-二氯乙烷时,UHMWPE微孔膜的孔径和孔隙率逐渐减小,但力学性能却逐渐提高.DSC法和WAXD法计算的微孔...     

Wear studies on the likely performance of CFR-PEEK/CoCrMo for use as artificial joint bearing materials

It is well known that a reduction in the volume of wear produced by articulating surfaces in artificial joints is likely to result in a lower incidence of failure due to wear particle induced osteolysis. Therefore, new materials have been introduced in an effort to produce bearing surfaces with lower, more biologically acceptable wear. Polyetheretherketone (PEEK-OPTIMA) has been successfully used in a number of implant applications due to its combination of mechanical strength and biocompatibility. Pin-on-plate wear tests were performed on various combinations of PEEK-OPTIMA and carbon fibre reinforced PEEK-OPTIMA (CFR-PEEK) against various CoCrMo alloys to assess the potential of this material combination for use in orthopaedic implants. The PEEK/low carbon CoCrMo produced the highest wear. CFR-PEEK against high carbon or low carbon CoCrMo provided low wear factors. Pin-on-plate tests performed on ultra-high molecular weight polyethylene (UHMWPE) against CoCrMo (using comparable test conditions) have shown similar or higher wear than that found for CFR-PEEK/CoCrMo. This study gives confidence in the likelihood of this material combination performing well in orthopaedic applications.     

Study of mechanical degradation of UHMWPE acetabular components due to clinical X-ray procedures

The use of multi-component femoral implants to replace the femur head and re-establish bone motion has been widespread since the 70s. Frequently these implants have spherical metallic heads made of, for example, 316-L stainless steel or Cr–Co alloys, which allow rotational motion towards a polymeric component (UHMWPE). One of the major causes of implant rejection is the generation of UHMWPE debris on the surface between the implant head and the polymeric component. The gamma ray sterilization of implants and the periodical X-ray medical control could contribute to premature degradation of the polymeric surface, resulting in increased wear and shortened lifetime of the implant. In this work we study the degradation degree of the polymeric UHMWPE component as function of the X-ray dose. The elasto-plastic deformation and recovery were carried out by means of a nanohardness tester equipment and the polymer degradation was measured using a fast Fourier transform infra-red (FT-IR) equipment. The results show the compromise among the irradiation doses, the surface oxidation and the mechanical properties of the samples.     

Effects of surface coating on reducing friction and wear of orthopaedic implants

Coatings such as diamond-like carbon (DLC) and titanium nitride (TiN) are employed in joint implants due to their excellent tribological properties. Recently, graphite-like carbon (GLC) and tantalum (Ta) have been proven to have good potential as coating as they possess mechanical properties similar to bones—high hardness and high flexibility. The purpose of this systematic literature review is to summarize the coating techniques of these four materials in order to compare their mechanical properties and tribological outcomes. Eighteen studies published between January 2000 and February 2013 have met the inclusion criteria for this review. Details of their fabrication parameters, material and mechanical properties along with the tribological outcomes, such as friction and wear rate, were identified and are presented in a systematic way. Although experiment conditions varied, we conclude that Ta has the lowest wear rate compared to DLC, GLC and TiN because it has a lower wear rate with high contact pressure as well as higher hardness to elasticity ratio. However, a further tribology test is needed in an environment which replicates artificial joints to confirm the acceptability of these findings.     

Impact of time-dependency on long-term material testing and modeling of polyethylene

Ultra-high molecular weight polyethylene (UHMWPE) has an important role in orthopaedic implants because of its favorable properties as an articulating surface. UHMWPE component testing often focuses on measuring the long-term fatigue or wear response of the material that could be realized during many years of use. However, the impact of time-dependent properties of UHMWPE on such tests is not well characterized. In particular, altering the frequency of loading and allowing for material creep or relaxation can significantly alter the stress/strain state of the material, and therefore affect long-term mechanical properties (e.g. wear, fatigue) that are dependent on the constitutive state. The goal of this work is to use advanced, validated material modeling of UHMPWE that incorporates time-dependent properties to explore the effects of frequency and rest time on the mechanical response of UHMWPE.     

Biotribological properties of UHMWPE grafted with AA under lubrication as artificial joint

Osteolysis caused by wear particles from polyethylene in the artificial hip joints is a serious issue. In order to endow the low friction and wear of the bearing surface of ultra-high molecular weight polyethylene (UHMWPE) artificial joint for a longer term, hydrophilic acrylic acid (AA) was grafted on UHMWPE powders with the method of ultraviolet irradiation and then the modified powders were hot pressed. The tribological properties of modified UHMWPE sliding against CoCrMo metallic plate on reciprocating tribometer under calf serum, saline and distilled water lubrication during a long-term friction were investigated. The measurement of Fourier-transform infrared spectroscopy indicates that AA is successfully grafted on the surface of UHMWPE powders by photo-induced graft polymerization. Contact angles of UHMWPE are decreased from 83° to 35° by grafting and the surface wettability is effectively improved. The tensile strength of modified sample decreases. The friction coefficient and wear rate of UHMWPE-g-PAA under calf serum, saline and distilled water lubrication are lower than that of untreated UHMWPE. With the increase of grafting ratio, the wear rate of UHMWPE-g-PAA decreases firstly and then increases. The modified UHMWPE with grafting ratio of 3.5 % has the lowest wear rate, which is just quarter of the untreated UHMWPE. The hydrated PAA polymer brushes enclosed in the UHMWPE bulk material provide continuous lubrication during long term sliding.     

Status of surface modification techniques for artificial hip implants

Surface modification techniques have been developed significantly in the last couple of decades for enhanced tribological performance of artificial hip implants. Surface modification techniques improve biological, chemical and mechanical properties of implant surfaces. Some of the most effective techniques, namely surface texturing, surface coating, and surface grafting, are applied to reduce the friction and wear of artificial implants. This article reviews the status of the developments of surface modification techniques and their effects on commonly used artificial joint implants. This study focused only on artificial hip joint prostheses research of the last 10 years. A total of 27 articles were critically reviewed and categorized according to surface modification technique. The literature reveals that modified surfaces exhibit reduced friction and enhanced wear resistance of the contact surfaces. However, the wear rates are still noticeable in case of surface texturing and surface coating. The associated vortex flow aids to release entrapped wear debris and thus increase the wear particles generation in case of textured surfaces. The earlier delamination of coating materials due to poor adhesion and graphitization transformation has limited the use of coating techniques. Moreover, the produced wear debris has adverse effects on biological fluid. Conversely, the surface grafting technique provides phospholipid like layer that exhibited lower friction and almost zero wear rates even after a longer period of friction and wear test. The findings suggest that further investigations are required to identify the role of surface grafting on film formation and heat resistance ability under physiological hip joint conditions for improved performance and longevity of hip implants.     

Wear of ultra-high molecular weight polyethylene against damaged and undamaged stainless steel and diamond-like carbon-coated counterfaces

The wear of ultra-high molecular weight polyethylene (UHMWPE) in artificial joints and the resulting wear debris-induced osteolysis remains a major clinical concern in the orthopaedic sector. Third-body damage of metallic femoral heads is often cited as a cause of accelerated polyethylene wear, and the use of ceramic femoral heads in the hip is gaining increasing favour. In the knee prostheses and for smaller diameter femoral heads, the application of hard surface coatings, such as diamond-like carbon, is receiving considerable attention. However, to date, there has been little or no investigation of the tribology of these coatings in simulated biological environments. In this study, diamond-like carbon (DLC) has been compared to stainless steel in its undamaged form and following simulated third-body damage. The wear of UHMWPE was found to be similar when sliding against undamaged DLC and stainless steel counterfaces. DLC was found to be much more damage resistant than DLC. Under test conditions that simulate third-body damage to the femoral head, the wear of UHMWPE was seven times lower against DLC than against stainless steel (P < 0.05). The study shows DLC has considerable potential as a femoral bearing surface in artificial joints.     

Effects of screen-grid bias voltage on the microstructure and properties of the ultrahigh molecular weight polyethylene (UHMWPE) modified by oxygen plasma

The specimens of ultrahigh molecular weight polyethylene (UHMWPE) were treated by oxygen plasma using a pulse-biased screen-grid technique under different negative bias conditions. The screen-grid was used to provide an electric field to accelerate the oxygen ions towards the UHMWPE substrate during the plasma treatment process. The effects of the screen-grid voltage on the surface microstructure, wettability, mechanical properties and wear resistance of UHMWPE were investigated. It was found that the degree of crosslinking, oxidation, wettability and surface roughness of UHMWPE can be increased with the increasing of the screen-grid voltage. Owing to the increase of the degree of crosslinking, the hardened layer formed on the surface of the UHMWPE samples was also strengthened greatly with the increase of the grid voltage. However, the wear results indicated that the UHMWPE sample modified at higher bias voltage exhibits poor wear performance, which could be mainly related to the embrittlement resulted from the aggravation of oxidation.     

Characterization of alendronate sodium-loaded UHMWPE for anti-osteolysis in orthopedic applications

Ultra-high molecule weight polyethylene (UHMWPE) loaded with alendronate sodium (ALN), a potential drug to prevent debris-induced osteolysis, was developed in our previous study. This study aims to investigate the wear performance of UHMWPE-ALNs. In this study, wear test, mechanical test, differential scanning calorimetry (DSC) and contact angle test were applied to characterize the wear performance, mechanical behavior and physical properties of UHMWPE-ALNs. The effect of ALN on the wear performance of UHMWPE-ALNs was investigated by scanning electron microscope (SEM), back scattering electrons (BSE) and energy dispersive X-ray spectrum (EDX). The results of wear test showed that the friction coefficient and volumetric loss of UHMWPE-ALN 0.5 wt.% were comparable with those of UHMWPE. The result of SEM-BSE-EDX revealed that the wear debris detached easily from the ALN-agglomerated regions, which was mainly responsible for the decrease of wear resistance of UHMWPE-ALN 1.0 wt.%. The loaded ALN resulted in the increase of hydrophilicity of UHMWPE-ALNs. The decrease of toughness and crystallinity of UHMWPE-ALN 1.0 wt.% attributed to the non-uniform distribution of ALN. The UHMWPE-ALN 0.5 wt.%, in which no ALN agglomeration was observed, possessed approving mechanical properties and wear performance, might have potential clinical application to prevent the debris-induced osteolysis in prosthetic joints.     

Radiation enhanced modification of HDPE for medical applications

Comparison of gamma irradiation induced change in properties in terms of thermal and mechanical properties between two grades of HDPE and UHMWPE was carried out. It was found that the responses to irradiation of two grades of HDPE investigated were close whereas a difference in response was found between HDPE and UHMWPE. The irradiation dose that caused the lowest wear and highest hardness for UHMWPE was 500 kGy. When irradiation dose was above 500 kGy, no significant changes in wear and hardness properties were observed. The irradiation dose for HDPE, both 2208J and 7000F, that caused the wear resistance and hardness comparable to irradiated UHMWPE at 500 kGy was 1000 kGy. In addition, the dose of 750 kGy was needed for HDPE to achieve the similar level of wear resistance as non-irradiated UHMWPE. ©2003 Kluwer Acadamic Publishers