以DCP和DTBP引发制备交联UHMWPE

分别以DcP和DTBP对UHMWPE进行交联改性,通过改变DcP或DTBP的用量、交联温度、交联时间等成型条件制备了模压烧结试样。结果表明：在DcP交联工艺中,DcP与U删1vPE质量比为0．15％、交联温度为155℃、时间为30min时,制品耐磨粒磨损性能最好;在DTBP交联工艺中,DTBP与UHMWPE质量比为O．50％、交联温度为140℃、时间为20min时,制品耐磨粒磨损性能最好。从改进耐磨粒磨损性能角度来说,采用DTBP交联工艺更好。     

辐照交联GO/UHMWPE复合材料在人工海水润滑介质下的摩擦学性能研究

为改善超高分子量聚乙烯(UHMWPE)在海水润滑介质下的耐磨损性能,采用氧化石墨烯(GO)填充与辐照交联对UHMWPE进行改性处理。利用摩擦磨损试验机研究了辐照前后UHMWPE与GO/UHMWPE复合材料在人工海水润滑介质下的摩擦学性能,利用扫描电子显微镜(SEM)与三维表面轮廓仪扫描试样磨痕表面形貌,计算其磨损率,并分析了其摩擦磨损机理。结果表明,在人工海水润滑介质下,GO填充与辐照交联改性处理均略微增加了UHMWPE的摩擦因数,降低了磨损率;二者共同使用可以协同增强UHMWPE的耐磨性能,降低复合材料的摩擦因数与磨损率; GO填充显著提高了UHMWPE的抗磨粒磨损与抗疲劳磨损性能;辐照交联改性处理进一步提高了GO/UHMWPE复合材料的抗磨粒磨损性能。     

DTBP含量对挤出成型过氧化物交联PE-HD的影响

利用锥形双螺杆熔融挤出二叔丁基过氧化物(DTBP)交联高密度聚乙烯(PE-HD)型坯,再借助高温加热装置对型坯进行后交联处理,最后得到耐温性较高的挤出成型过氧化物交联PE-HD型材.通过对试样交联度、热变形温度、力学性能和差示扫描量热(DSC)测试及表征,探究了不同DTBP含量对挤出成型过氧化物交联PE-HD试样性能的...     

交联体系对超高摩尔质量聚乙烯性能的影响

采用两种适用于不同温度的交联体系对超高摩尔质量聚乙烯(UHMWPE)材料进行改性,并对其性能进行研究。结果表明,交联体系的引入可在基体材料中形成交联网络,从而显著提高UHMWPE的承载能力、抗蠕变性及耐热性,同时保持良好的结晶性、韧性和热稳定性;交联温度接近成型温度的交联体系B改性UHMWPE材料的综合性能较优,尤其是机械性能;交联体系引发剂最佳用量均为0.2~0.3份,而后力学性能急剧下降,与引发剂的适用温度无关。     

不同成型方式下UHMWPE耐热改性进展

介绍了近年来超高分子量聚乙烯(UHMWPE)在模压成型、挤出成型、注塑成型方面的耐热改性研究进展,分析了采用不同成型方法对UHMWPE耐热改性的方法及改性效果。关于UHMWPE模压与挤出成型的耐热改性方法主要包括物理改性(填充改性、共混改性、共混填充改性)、化学改性(过氧化物交联、偶联剂交联、辐射交联)、聚合填充复合改性,而UHMWPE的注塑成型耐热改性研究较少。对UHMWPE进行耐热改性,加入的改性材料后,能显著提高复合材料耐热性,但是,部分材料的加入却降低了UHMWPE耐磨性、抗冲击性等性能,需要对UHMWPE注塑成型的耐热改性及改性材料的选用进一步研究。最后,对UHMWPE的耐热改性的发展趋势进行了展望。     

过氧化物交联UHMWPE的动力学与结晶行为的研究

采用过氧化二异丙苯(DCP)交联改性超高相对分子质量聚乙烯(UHMWPE),通过差示扫描量热和广角X射线衍射测试,研究了DCP交联UHMWPE的反应动力学以及DCP含量对交联UHMWPE片材的热性能、结晶性能和晶粒尺寸的影响。结果表明:DCP与UHMWPE交联反应为放热反应,其非等温交联反应符合一级反应,反应活化能随着DCP含量的增加而降低;随着DCP含量的增加,交联UHMWPE片材的结晶度、重结晶度、熔点和结晶温度均降低,结晶峰强度和晶粒尺寸减小,当DCP质量分数为2. 5%时,交联UHMWPE片材(110)晶面和(200)晶面所对应的晶粒尺寸分别降低至18. 6 nm和12. 1 nm。     

羧甲基纤维素和TDI共同改性聚乙烯醇胶粘剂的研究

以甲苯二异氰酸酯(TDI)为交联剂,制备了TDI交联改性羧甲基纤维素(CMC)和聚乙烯醇(PVA)混合胶粘剂体系,并在交联反应完成后,用硼砂消乳增稠。采用正交试验法探讨了主要原材料配比、交联反应温度和交联反应时间等工艺条件对改性PVA胶粘剂性能的影响。研究结果表明:当PVA为12 g/100 m L、CMC为1.6 g/100 m L、TDI为4.00 m L/100 m L、硼砂为0.8 g/100 m L、交联反应温度为40℃和交联反应时间为90 min时,改性PVA胶粘剂具有良好的综合性能,其颜色稳定性及储存稳定性较佳,对木制品的粘接强度相对最好。     

辐照交联及老化对GO/UHMWPE复合材料生物摩擦学性能的影响

采用改良Hummer法制备了氧化石墨烯(GO),通过热压成型工艺制备了GO/超高分子量聚乙烯(UHMWPE)复合材料,在真空环境下采用γ射线对其进行辐照交联处理,并将部分样品置于80℃环境下加速老化处理21d。利用摩擦磨损实验机研究了复合材料在小牛血清润滑介质下的摩擦学性能;利用扫描电子显微镜(SEM)和三维表面轮廓仪观察试样表面磨痕并计算相应的磨损率。结果表明,在小牛血清润滑介质下,GO填充与辐照交联改性处理可以降低UHMWPE的摩擦因数和磨损率,协同提高其耐磨性,但对摩擦因数的影响并不显著。加速老化处理显著增加辐照UHMWPE及辐照GO/UHMWPE复合材料的摩擦因数和磨损率,降低了其摩擦磨损性能。GO填充降低了辐照UHMWPE在加速老化处理后摩擦因数和磨损率,增强了其摩擦学性能。     

填料填充UHMWPE交联塑料磨粒磨损性能研究

本文采用二氧化硅、炭黑和还原铁粉三种填料对UHMWPE交联体系进行填充改性,采用模压烧结成型法制备了改性UHMWPE交联塑料,实验结果表明:三种填料对磨损率的影响比较一致,当二氧化硅含量6%、炭黑含量8%、还原铁粉含量2%时,磨粒磨损率最小。在磨粒磨损实验中,还原铁粉的含量对磨粒磨损率的影响最大。     

超高分子量聚乙烯注塑制品的力学性能及微观形态

通过共混改性制备了注塑级复合材料,研究了超高分子量聚乙烯(ultra high molecular weight polyethylene,UHMWPE)基料份数、交联剂添加量、低分子量聚烯烃分子量分布对注塑级复合材料加工性能以及力学性能的影响。利用低分子量聚烯烃改性UHMWPE树脂,制备了注塑级复合材料,实现了UHMWPE的注塑成型。结果表明:流动改性剂的添加量应大于30%,交联剂的质量分数应小于2.5%,UHMWPE树脂基料的质量分数应小于65%。此外,还通过偏光显微镜照片研究了注塑制品的微观形态,发现注塑成型的制品微观形态与传统挤出成型不同,其微观相界面依然存在,且由于交联反应,注塑制品熔融结晶后无法生成较大晶粒。     

Oxidation resistance and abrasive wear resistance of vitamin E stabilized radiation crosslinked ultra‐high molecular weight polyethylene

The effect of gamma radiation on the oxidation and wear resistance of ultra‐high molecular weight polyethylene (UHMWPE) has been extensively studied since these properties are critical for the longevity of UHMWPE components of total joint replacement prostheses. While gamma radiation increases wear resistance of UHMWPE, the free radical generated in the lamellar regions by radiation must be stabilized before oxidative degradation occurs as the polymer ages. Initially, post‐radiation melting conducted to quench free radicals but this treatment also decreases its mechanical properties. Recently, it has been replaced by incorporation of Vitamin E into UHMWPE to combat oxidative degradation. In this study, we assessed wear resistance of Vitamin E stabilized UHMWPE under abrasive wear conditions and oxidation resistance by shelf‐aging irradiated components for 2 years. Equilibrium swelling experiments showed that Vitamin E decreased crosslink density, which affected wear resistance, but oxidation resistance was better preserved with increasing concentration of Vitamin E. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44125.     

Wear resistant UHMWPE with high toughness by high temperature melting and subsequent radiation cross-linking

The goal of this study was to create wear resistant ultra high molecular weight polyethylene (UHMWPE) with improved strength and toughness. It was previously demonstrated that high temperature melting (HTM) of UHMWPE at 280-320 °C improved its toughness without detrimentally affecting its wear resistance. We hypothesized that radiation cross-linking after high temperature melting could further improve the wear resistance of UHMWPE, and the loss in toughness by radiation cross-linking could be compensated by the improved toughness achieved by the high temperature melting prior to irradiation. In this work, we demonstrated that irradiation after HTM generated UHMWPE with improved toughness compared to the irradiated UHMWPEs without HTM, partly due to the low cross-link density of irradiated HTM UHMWPE. At a given cross-link density, irradiated HTM UHMWPEs showed higher wear resistance than irradiated UHMWPE. Therefore, successive HTM and radiation cross-linking strategy is promising to create UHMWPE materials with low wear and improved mechanical properties for total joint implants.     

A study on sliding wear of ultrahigh molecular weight polyethylene/polypropylene blends

The wear and friction behavior of ultrahigh molecular weight polyethylene (UHMWPE)/ polypropylene (PP) blends was studied. The addition of PP improves processability and the anti‐wear properties of UHMWPE. The friction coefficient and wear rate of pure UHMWPE are much higher than those of UHMWPE/PP blends under the same conditions, and the wear rate of UHMWPE is more sensitive to load and wear time than that of the UHMWPE/PP blend. Long scratch grooves and cracks occurred in the worn surface of UHMWPE, while no such serious damage was observed in the worn surface of the UHMWPE/PP blend. Atomic Force Micrograph using the contact mode indicated that the friction force between pure UHMWPE and Si₃N₄ tip is much higher than that for the UHMWPE/PP blend, which is consistent with the results from macro‐friction testing.     

硫化胶在高温沥青中结构与性能的研究

采用NR、SBR硫化胶代替废胶粉粉末,在高温沥青(163℃)中进行热存储,测试了不同热存储时间下硫化胶的溶胀指数、交联密度、溶胶含量、硬度、拉伸强度等性能,研究了硫化胶在高温沥青中的结构与性能变化。结果表明,硫化胶在高温沥青中经过一个快速增长而后趋于平缓的溶胀过程;在高温和溶胀作用下,橡胶发生降解,交联密度呈快速下降而后缓慢降低的趋势,溶胶含量随着交联密度的降低显著增加;在溶胀和降解双重作用下,硫化胶硬度、力学性能显著下降。     

流动改性剂对UHMWPE流动及磨损性能的影响研究

研究了聚乙烯(LDPE、HDPE)、聚丙烯(PP)及尼龙(PA)对超高分子量聚乙烯(UHMWPE)流动及磨损性能的影响,发现流动性越好的聚乙烯对UHMWPE流动性改进越大,且加入比例越高,共混物的流动性越好;当HDPE组分小于50％时,对UHMWPE磨损性能影响很小,而LDPE则大大损害了共混物的磨损性能。均聚PP比共聚PP对UHMWPE的流动性改进更大,但使其磨损性能大大降低。PA含量在40％以下对UHMWPE的流动性改进不大,对磨损性能影响也很小。     

Effect of γ-radiation on the dynamic mechanical properties of silicone rubbers

Dimethyl-, trifluoropropyl-, and high phenyl content polysiloxanes were irradiated in a ⁶⁰Co source to doses of 100 Mrad. The hardness of the specimens increased with dose. Crosslink density changes did not directly reflect the hardness changes. The crosslink density of the dimethyl polymer increased significantly and that of the trifluoropropyl polymer increased only slightly. There was a slight decrease in the crosslink density of the aromatic material. The storage moduli reflected the changes in crosslink density. Loss moduli of the dimethyl- and trifluoropropylpolysiloxanes initially decreased and then increased on continuing irradiation. Dynamic moduli of the high aromatic content polymer were essentially unchanged by the radiation. All the dynamic data were correlated by the WLF time–temperature relationship.     

The influence of several silicates on the fretting behavior of UHMWPE composites

Five kinds of silicates (attapulgite, kaolin, montnorillonite, synthetic mica, and talc) reinforced ultra-high molecular weight polyethylene (UHMWPE) composites were prepared. The fretting performance of the composites was investigated using an oscillating reciprocating friction and wear tester in a ball-on-plate mode. The thermodynamic property and crystallinity of the composites were evaluated, and the worn morphology was also observed. Result shows that the heat-resistance and the crystallinity of the composites are generally improved. The friction coefficient and mass loss of the composites reduced than those of the neat UHMWPE. Thereinto, the attapulgite/UHMWPE composite shows the best fretting resistance performance. The heat resistance of composites increases due to the reinforcement of silicates. Meantime, the friction load can be distributed by the filler in the matrix. Moreover, the different fretting resistance performance of the composites is due to the different dispersion degree and the interfacial bonding force between the fillers and the UHMWPE matrix.     

新型抗高温水溶性暂堵剂实验研究

高温120℃下,使用不同分子量和水解度的聚丙烯酰胺与多种交联剂按照不同比例进行交联反应,得到高温暂堵剂体系,通过对暂堵剂的成冻时间、稳定时间和破胶时间等因素的研究,确定暂堵剂体系的聚合物为PAM1200,聚合物质量浓度为0.4%～0.55%;交联剂为G与YG107(2∶1)复配体,质量浓度为0.1%～0.2%,破胶剂质量浓度0.03%～0.05%。在120℃0,.5%PAM1200,0.1%交联剂G,0.2%交联剂YG107,0.03%破胶剂下,稳定性评价实验及岩心流动实验表明:暂堵剂对不同渗透率的岩心封堵率达92.75%,暂堵后渗透率恢复率高于83.19%,具有较好的破胶液化能力。     

An investigation on wear behavior of UHMWPE/carbide composites at elevated temperatures

Ultra-high molecular weight polyethylene (UHMWPE) is extensively used in frictional applications due to its advanced wear resistance. This advanced polymer is reinforced with hard particulate fillers for further developments against wear conditions. Since elevated temperatures prevail in the service conditions, wear behavior of UHMWPE composites is an important issue for the engineering applications. In the present work, UHMWPE-based composites including silicon carbide (SiC) fillers were fabricated in a compression molding chamber. In the specimen preparation stage, molding pressure, filler amount, and filler particle size were varied to investigate the influence of these variables. Upon deciding the optimum parameters from the wear tests conducted at room temperature, the wear experiments were repeated for the optimum specimen at elevated temperatures, such as 40 and 60°C. According to the results, the wear behavior of the SiC/UHMWPE composites is heavily changed by the effect of elevated temperature. Adhesive effect is pronounced at elevated temperatures while the wear characteristics possess the abrasive effect in the sliding path. In addition, the composites exhibit an accelerated material loss as temperature increases during the frictional system.     

Synthesis and characterization of CNTs/POM nanocomposite acetabular hip cup

Polyoxymethylene (POM) considered as the most appropriate alternative for ultra-high molecular weight polyethylene (UHMWPE) in the hip joint replacement application due to their biocompatibility, high mechanical properties, and cheapness. The wear is the main cause of the failure in the hip joint and the wear resistance of UHMWPE is still better than the wear resistance of POM. This research aims to improve the wear behavior of POM by blending it with 0.02?wt% of functionalized carbon nanotubes (CNTs) and using paraffin oil dispersion technique to obtain a uniform dispersion. The injection molding and machining process were used to produce the new (CNTs/POM) nanocomposite acetabular hip cup which has a high wear performance. The wear rate of the CNTs/POM cups was evaluated using a total leg joint’s simulator at 1,000?N for 3 million cycles under serum-based lubricated conditions. Moreover, the wear mechanism of cups was examined by scanning electron microscopy as well as the dispersion of CNTs inside the cup matrix. The results show that the wear resistance of POM cup has been improved by adding functionalized CNTs ～402% and ～221%, when compared with a virgin POM and UHMWPE, respectively, because of increasing the melting temperature and crystallinity degree.