Small range 文档类型:"3"

Totally found 8324 items.

  • [期刊] 偶联修饰纳米蒙脱土/超高分子量聚乙烯基复合材料的摩擦磨损性能
    通过模压烧结法制备了超高分子量聚乙烯(ultra-high molecular weight polyethylene,UHMWPE)与硅烷(silane,s)和钛酸酯(titanate,t)偶联剂修饰的纳米蒙脱土(nano-montmorillonite,nano-MMT)复合材料,nano-MMT含量由0到15%(质量分数,下同).采用45#钢为摩擦对偶件的往复滑动式摩擦磨损试验机,在室温干摩擦条件下测试了复合材料的摩擦学性能,实验条件为:接触压力P=8.0 kN、滑动速度v=1.8 m/min、时间t=3 h;用扫描电镜观察了复合材料磨损表面的形貌并分析了磨损机理.结果表明:随nano-MMT含量的增加,偶联修饰的nano-MMT/UHMWPE复合材料的硬度、摩擦系数和磨损率增加;偶联修饰改善了复合材料的摩擦学性能;与钛酸酯相比,硅烷偶联修饰nano-MMT/UHMWPE复合材料的硬度和摩擦学性能更好.用5%硅烷偶联修饰的nano-MMT,5%钛酸酯偶联剂修饰的nano-MMT和5%nano-MMT增强的UHMMPE复合材料的摩擦系数μ、摩擦温度θ、磨损率W分别为:μs=0.124,μt=0.135,μ=0.180;θs=92℃,θt=96 ℃,θ=94 ℃;Ws=4.25×10-7 mm3/(N·m),Wt=6.31×10-7 mm3/(N·m),W=18.80×10-7 mm3/(N·m);两种偶联修饰复合材料的表面磨损情况相似,含5%nano-MMT的复合材料主要表现为粘着磨损,而含15%nano-MMT的复合材料主要表现为表层和亚表层的脆性疲劳断裂.
  • [期刊] Dynamic Compressive and Tensile Characteristics of a New Type of Ultra-High-Molecular Weight Polyethylene (UHMWPE) and Polyvinyl Alcohol (PVA) Fibers Reinforced Concrete
    The dynamic mechanical properties of concrete materials are important parameters for evaluating the safety performance of concrete structures under dynamic loads. Fiber cement-based materials have been widely used in the construction projects due to their strength, toughening, and cracking resistance. In this study, we conducted experimental and theoretical studies on dynamic compression and tensile mechanical properties of different proportions of new-type fiber concrete. A Split-Hopkinson pressure bar equipment was used to determine the concrete behavior at different strain rates. The effects of strain rate and fiber content on the strength of the specimen, dynamic increase factor, and ultimate strain were analyzed. Based on the macrodamage factor, the traditional nonlinear viscoelastic constitutive model was simplified and improved. The four-parameter constitutive model was obtained, and the influence of these parameters on the performance of fiber concrete was analyzed. The experimental results were compared with those predicted from the available equations, and results were in accordance. Finally, an analytical equation for predicting the dynamic compression and tensile properties of these new-type fibers was proposed.
  • [期刊] The Effect of High Dose of Gamma-Irradiation on Residual Radicals Concentration in Ultra-High Molecular Weight Polyethylene (UHMWPE) in the Presence of Vitamin E
    Powder samples of UHMWPE (GUR 1020) containing 0.1% by wt. vitamin E (α-tocopherol, α-T) were irradiated at room temperature in air for doses of 30-kGy, 65-kGy or 100-kGy (~~(60)Co). After irradiation, they were stored at —78.5°C (dry ice temperature) for one year and then opened to air at room temperature. Following the decay of the primary alkyl and allyl radicals (at room temperature in air), growth of the carbon-centered polyenyl Rl (—·CH+CH=CH+_m, m ≥ 3), and the oxygen-centered di- ortri-enyl R2 (—·OCH+CH=CH+_m, m ≤3) residual radicals were measured for eight weeks. An X-band electron spin resonance (ESR) spectrometer was used for radical measurements. The initial relative radical concentrations (R2/R1) were found to be 10.13, 4.6 and 3.7 for the 65-kGy, 30-kGy and 100-kGy samples, respectively. Rl and R2 were both found to grow significantly in the 65-kGy samples while they grew only slightly in the 30-kGy and 100-kGy samples. In 65-kGy sample, Rl grew faster than R2 and the relative concentration R2/R1 was reduced from 10.13 to 2.9 for the 65-kGy sample while that forthe 30-kGy and 100-kGy samples reduced only slightly, from 4.6 to 3.5 and 3.7 to 3.2, respectively. The behavior of the residual radicals can be explained by Raman spectroscopic data which suggest that the 65-kGy samples had a higher percentage of amorphous regions when compared to the 30-kGy or 100-kGy (21.7% compared to 15.7% or 17.9%) and also suggest a lower percentage of inter-phase regions (16.4% compared to 25.6% or 17.5%) and a lower level of structural disorder (0.26% compared to 0.44% or 0.27%).
  • [期刊] Effect of grafted poly [2-methacryloyloxyethyl phosphorylcholine (MPC)] on tribological properties of ultra-high molecular weight polyethylene (UHMWPE)
    2-methacryloyloxyethyl phosphorylcholine (MPC) polymers have good biocompatibility and hydrophilicity because the function of the phospholipid polar groups of MPC side-chain is similar to the natural articular cartilage. MPC has a potential application on surface modification of artificial joints. In this research, MPC was grafted on ultra-high molecular weight polyethylene (UHMWPE) by the photo-induced graft polymerization to form poly 2-methacryloyloxyethyl phosphorylcholine (PMPC) layer. The microstructure of PMPC layer was studied by Fourier-transform infrared (FT-IR) spectroscopy with attenuated total reflection (ATR) equipment, X-ray photoelectron spectroscopy (XPS). The surface wettability of PMPC layer was evaluated by the contact angle test. The wear resistance of MPC modified UHMWPE was evaluated by the wear test. The results show that the PMPC layer has a good lubricating effect and it can reduce the friction coefficient effectively. The benzophenone pretreatment time is an important factor in the graft stability of MPC.
  • [期刊] Ultra-High-Molecular-Weight Polyethylene (UHMWPE) in Total Joint Arthroplasty
    Total joint arthroplasty of the hip and knee are successful orthopedic procedures that reduce pain and improve mobility in patients. As the implanted materials used in these procedures have improved, the lifetime of the implants has now reached more than 20 years. Younger patients are undergoing total joint arthroplasty at increasing rates, which has increased the need for improvements in materials for extended implant longevity. In this review, we aim to provide historical perspective on the evolution of ultra-high-molecular-weight polyethylene in total joint arthroplasty. We review this material with respect to its structure, mechanical properties, wear rates, sterilization effects, cross linking, and other new polymer innovations. Ultra-high-molecular-weight polyethylene (UHMWPE) has been a cornerstone for total joint arthroplasty and with continued design improvements will continue to be vital to this successful orthopedic operation.
  • [期刊] Tribological properties of ultrahigh-molecular-weight polyethylene (UHMWPE) composites reinforced with different contents of glass and carbon fibers
    Purpose This purpose of this study was to investigate the effects of carbon fiber (CF) and/or glass fiber (GF) fillers on the tribological behaviors of ultrahigh-molecular-weight polyethylene (UHMWPE) composites to develop a high-performance water-lubricated journal bearing material. Design/methodology/approach Tribological tests were conducted using a pin-on-disc tribometer using polished GCr15 steel pins against the UHMWPE composite discs under dry conditions with a contact pressure of 15 MPa and a sliding speed of 0.15 m/s. Scanning electron microscopy, laser 3D micro-imaging profile measurements and energy-dispersive X-ray spectrometry were used to analyze the morphologies and elemental distributions of the worn surfaces. Findings The results showed that hybrid CF and GF fillers effectively improved the wear resistance of the composites. The fiber fillers decreased the contact area, promoted transfer from the polymers and decreased the interlocking and plowing of material pairs, which contributed to the reduction of both the friction coefficient and the wear rate. Originality/value The UHMWPE composite containing 12.5 Wt.% CF and 12.5 Wt.% GF showed the best wear resistance of 2.61 x 10(-5) mm(3)/(N center dot m) and the lower friction coefficient of 0.12 under heavy loading. In addition, the fillers changed the worn surface morphology and the wear mechanism of the composites.
  • [期刊] Tribological properties of ultrahigh-molecular-weight polyethylene (UHMWPE) composites reinforced with different contents of glass and carbon fibers
    Purpose This purpose of this study was to investigate the effects of carbon fiber (CF) and/or glass fiber (GF) fillers on the tribological behaviors of ultrahigh-molecular-weight polyethylene (UHMWPE) composites to develop a high-performance water-lubricated journal bearing material. Design/methodology/approach Tribological tests were conducted using a pin-on-disc tribometer using polished GCr15 steel pins against the UHMWPE composite discs under dry conditions with a contact pressure of 15 MPa and a sliding speed of 0.15 m/s. Scanning electron microscopy, laser 3D micro-imaging profile measurements and energy-dispersive X-ray spectrometry were used to analyze the morphologies and elemental distributions of the worn surfaces. Findings The results showed that hybrid CF and GF fillers effectively improved the wear resistance of the composites. The fiber fillers decreased the contact area, promoted transfer from the polymers and decreased the interlocking and plowing of material pairs, which contributed to the reduction of both the friction coefficient and the wear rate. Originality/value The UHMWPE composite containing 12.5 Wt.% CF and 12.5 Wt.% GF showed the best wear resistance of 2.61 x 10(-5) mm(3)/(N center dot m) and the lower friction coefficient of 0.12 under heavy loading. In addition, the fillers changed the worn surface morphology and the wear mechanism of the composites.
  • [期刊] Dynamic Compressive and Tensile Characteristics of a New Type of Ultra-High-Molecular Weight Polyethylene (UHMWPE) and Polyvinyl Alcohol (PVA) Fibers Reinforced Concrete
    The dynamic mechanical properties of concrete materials are important parameters for evaluating the safety performance of concrete structures under dynamic loads. Fiber cement-based materials have been widely used in the construction projects due to their strength, toughening, and cracking resistance. In this study, we conducted experimental and theoretical studies on dynamic compression and tensile mechanical properties of different proportions of new-type fiber concrete. A Split-Hopkinson pressure bar equipment was used to determine the concrete behavior at different strain rates. The effects of strain rate and fiber content on the strength of the specimen, dynamic increase factor, and ultimate strain were analyzed. Based on the macrodamage factor, the traditional nonlinear viscoelastic constitutive model was simplified and improved. The four-parameter constitutive model was obtained, and the influence of these parameters on the performance of fiber concrete was analyzed. The experimental results were compared with those predicted from the available equations, and results were in accordance. Finally, an analytical equation for predicting the dynamic compression and tensile properties of these new-type fibers was proposed.
  • [期刊] UHMWPE:“卡”不住的战略材料——访中国纺织科学研究院有限公司原副总工程师、生物源纤维制造技术国家重点实验室主任孙玉山
    近些年,UHMWPE在民用领域的应用也在逐渐扩大,如航海装备、轨道交通、工具制造和防护用品等领域,因此其未来市场前景被一致看好。随着国内UHMWPE技术和产业的快速发展,这一材料已日渐显现出突破国外对我国高端产品封锁的迹象,国外想"卡"也卡不住。超高分子量聚乙烯纤维(Ultra High Molecular Weight Polyethylene Fiber,UHMWPE)与碳纤维和芳纶纤维并称世界"3大高科技特种纤维",UHMWPE又被称为"高强高模聚乙烯纤维"或
  • [期刊] Kevlar/UHMWPE混杂纤维复合材料抗弹性能
    研究芳纶/超高分子量聚乙烯(Ultra High Molecular Weight Polyethylene,简称"UHMWPE")纤维层间混杂复合材料对防弹性能的影响,采用LS-DYNA非线性动态显式有限元软件对不同迎弹面及不同混杂比的复合材料进行理论分析,模拟弹头侵彻层间混杂复合材料靶板的过程,得出复合材料的应力和变形演化图。通过实验验证迎弹面以及混杂比对防弹性能的影响,研究纤维的断裂形貌,进一步分析靶板的破坏机理。结果表明:以芳纶纤维作迎弹面时混杂复合材料防弹性能较好,且混杂比为1∶2时复合材料整体防弹性能可进一步提升。
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