Mechanical properties study of micro‐ and nano‐hydroxyapatite reinforced ultrahigh molecular weight polyethylene composites

This is a comparative study between ultrahigh molecular weight polyethylene (UHMWPE) reinforced with micro‐ and nano‐hydroxyapatite (HA) under different filler content. The micro‐ and nano‐HA/UHMWPE composites were prepared by hot‐pressing method, and then compression strength, ball indentation hardness, creep resistance, friction, and wear properties were investigated. To explore mechanisms of these properties, differential scanning calorimetry, infrared spectrum, wettability, and scanning electron microscopy with energy dispersive spectrometry analysis were carried out on the samples. The results demonstrated that UHMWPE reinforced with micro‐ and nano‐HA would improve the ball indentation hardness, compression strength, creep resistance, wettability, and wear behavior. The mechanical properties for both micro‐ and nano‐HA/UHMWPE composites were comparable with pure UHMWPE. The mechanical properties of nano‐HA/UHMWPE composites are better compared with micro‐HA/UHMWPE composites and pure UHMWPE. The optimum filler quantity of micro‐ and nano‐HA/UHMWPE composites is found to be at 15 wt % and 10 wt %, separately. The micro‐ and nano‐HA/UHMWPE composites exhibit a low friction coefficient and good wear resistance at this content. The worn surface of HA/UHMWPE composites shows the wear mechanisms changed from furrow and scratch to surface rupture and delamination when the weight percent of micro‐ and nano‐HA exceed 15 wt % and 10 wt %. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42869.     

Mechanism of filler action in reducing the wear of PTFE polymer by differential scanning calorimetry

Two types of representative nanometer materials, i.e., fibroid nanometer attapulgite and approximate spherical ultrafine diamond, were selected as fillers of polytetrafluoroethylene (PTFE) to study the mechanism of the wear‐reducing actions of the fillers in PTFE composites. The friction and wear tests were performed on a block‐on‐ring wear tester under dry sliding conditions. Differential scanning calorimetry (DSC) was used to investigate material microstructure and to examine modes of failure. No significant change in coefficient of friction was found, but the wear rate of PTFE composites was orders of magnitude less than that of pure PTFE. DSC analysis revealed that nanometer attapulgite and ultrafine diamond played a heterogeneous nucleation role in PTFE matrix and consequently resulted in increasing the crystallinity of PTFE composites. Moreover, the PTFE composite with higher heat absorption capacity and crystallinity exhibited improved wear resistance. A propositional “sea‐frusta” frictional model explained the wear mechanism of filler action in reducing the wear of PTFE polymer, i.e., fillers in the PTFE matrix effectively reduced the size of frictional broken units for PTFE composites and restrained the flowability of the units, as well as supporting the applied load. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Improvement of the tribological behavior of ultra‐high‐molecular‐weight polyethylene by incorporation of poly (phenyl p‐hydroxyzoate)

Ultra‐high‐molecular‐weight polyethylene/poly (phenyl p‐hydroxyzoate) composites (coded as UHMWPE/PPHZ) were prepared by compression molding. The effects of the poly (phenyl p‐hydroxyzoate) on the tribological properties of the UHMWPE/PPHZ composites were investigated, based on the evaluations of the tribological properties of the composites with various compositions and the examinations of the worn steel surfaces and composites structures by means of scanning electron microscopy and transmission electron microscopy. It was found that the incorporation of the PPHZ led to a significant decrease in the wear rate of the composites. The composites with the volume fraction of the PPHZ particulates within 45% ～ 75% showed the best wear resistance. The friction coefficient of the UHMWPE/PPHZ composites decreased with increasing load and sliding velocity, while the wear rates increased with increasing load. This was attributed to the enhanced softening and plastic deformation of the composites at elevated load or sliding velocity. The UHMWPE/PPHZ composites of different compositions had differences in the microstructures and the transfer film characteristics on the counterpart steel surface as well. This accounted for their different friction and wear behaviors. The transfer film of the UHMWPE/PPHZ composites appeared to be thinner and more coherent, which was largely responsible for their better wear resistance of t composite than the UHMWPE matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 96: 2336–2343, 2005     

Molecular dynamics simulation of α-ZrP/UHMWPE blend composites containing compatibilizer and its tribological behavior under seawater lubrication

In this work, blended composites with ultra-high molecular weight polyethylene (UHMWPE) as matrix polymer, α-zirconium phosphate (α-ZrP) as filler, and sodium polyacrylate (PAANa) as compatibilizer were prepared. The interfacial interaction between PAANa as a compatibilizer and the components of α-ZrP/UHMWPE was studied by molecular dynamics simulation. The friction and wear behavior of the GCr15 ball/composite friction pair under seawater lubrication under different loads were explored, and the friction and wear mechanism were analyzed. The results show that PAANa as a compatibilizer can effectively improve the interfacial interaction force between components of PAANa/α-ZrP/UHMWPE composites. The composites exhibited different trends regarding the relationship between tribological properties and α-ZrP content under various loads. The wear mechanism of composites under low load is mainly represented by extrusion deformation. With the increase of load, the wear mechanism of composites gradually changed into adhesive wear and abrasive wear (depending on the content of α-ZrP). This work provides a theoretical basis for preparing and applying other α-ZrP/polymer blend composites.     

纳米SiO2包覆SiC填充改性UHMWPE的热性能

采用纳米粒子表面包覆处理技术制备了纳米碳化硅/超高摩尔质量聚乙烯(SiC/UHMWPE)复合材料,并用傅立叶红外光谱(FTIR)、扫描电镜(SEM)、透射电镜(TEM)、热重分析(TG)和差示扫描量热(DSC)进行了测试表征。结果表明:纳米SiC经包覆处理后表面有一层均匀致密的SiO2,包覆处理能改善SiC在UHMWPE基体中的分散效果。当SiC质量分数为5%时,UHMWPE/SiC复合材料具有较高的耐热性能和热导率,这是由于纳米粒子包覆改性纳米SiC与UHMWPE基体均匀分散并形成良好的结合界面,增加了填料对UHMWPE的成核作用,提高其结晶度和耐热性能。     

超高相对分子质量聚乙烯对双峰HDPE树脂性能的影响

为了提高双峰高密度聚乙烯（HDPE）的力学性能,采用超高相对分子质量聚乙烯（UHM—WPE）与双峰HDPE以不同比例共混,对共混物的相对分子质量及其分布、热性能、流变性能和力学性能进行了测试。UHMWPE的加入使高相对分子质量部分显著增加,流变性能下降,添加量小于10％（质量分数）时,共混物粘度在高剪切速率下变化不大;UHMWPE可提高共混物的熔融温度和初始结晶温度,结晶度先增加然后迅速降低;随着UHMWPE含量的增加,混合物的拉伸强度也随之增加,呈线性关系;结晶度与冲击强度成反比。     

Preparation and friction properties of PBT/MMT composites

Poly(butylene terephthalate)/clay composites were prepared by direct melt compounding. Two structures were formed as confirmed by XRD and transmission electron microscopy. The presence of MMT layers does not change the crystal structure and the degree of crystallinity of PBT matrix. The tribological behaviors of neat PBT and PBT/clay composites were studied by the means of a pin‐on‐disk apparatus. It was found that the intercalation of organoclay could help reduce the friction coefficient and the specific wear rate of PBT, while the addition of natural clay was harmful to the friction coefficient and wear resistance of the polymer matrix. The different tribological behaviors of the composites are due to their different morphologies and the difference in the interfacial adhesion between the matrix and the clay platelets. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effect of surface modification of Kevlar fibre on friction and wear properties of UHMWPE composites

Abstract

The effects of Kevlar fibre additions and, particularly, the surface modification of the Kevlar fibres, on the sliding wear behaviour of the ultra high molecular weight polyethylene (UHMWPE) composites were investigated. The results showed that the sliding friction coefficient of the UHMWPE composites increased with the fibre content increase. The wear resistance of the UHMWPE composite was highest when the Kevlar fibre content was ～10 vol.-% and decreased as the applied normal load was increased. It was found that the silane modification of the Kevlar fibres improved the wear resistance and tensile strength of the UHMWPE composites as well.     

Effects of a coupling agent on the mechanical and thermal properties of ultrahigh molecular weight polyethylene/nano silicon carbide composites

Ultra‐high‐molecular‐weight polyethylene (UHMWPE)/nano silicon carbide (nano‐SiC) composites were prepared by compression molding. The effects of a coupling agent and the content of the filler on the filler dispersion and the mechanical and thermal properties of the composites were investigated. The results show that the mechanical properties of the composites first increased and then decreased with increasing SiC content. The macromolecular coupling agent exhibited a much better reinforcing effect than the small‐molecule coupling agent. The tensile strength of the composites with 3‐aminopropyltriethoxysilane (KH550), γ‐methacryloxypropyltrimethoxysilane (KH570), and silicone powders reached its maximum value when the silicon carbide (SiC) content was 3%. We found that a web of the UHMWPE/SiC/coupling agent was formed and played a significant role in improving the heat resistance of the composites. In addition, appropriate amounts of SiC could increase the crystallinity of UHMWPE via a process of heterogeneous nucleation. The comprehensive performance of the KH550/silicone/SiC/UHMWPE composites was the best. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Surface modification of ultra‐high‐molecular‐weight polyethylene. II. Effect on the physicomechanical and tribological properties of ultra‐high‐molecular‐weight polyethylene/poly(ethylene terephthalate) composites

We performed surface modification of ultra‐high‐molecular‐weight polyethylene (UHMWPE) through chromic acid etching, with the aim of improving the performance of its composites with poly(ethylene terephthalate) (PET) fibers. In this article, we report on the morphology and physicomechanical and tribological properties of modified UHMWPE/PET composites. Composites containing chemically modified UHMWPE had higher impact properties than those based on unmodified UHMWPE because of improved interfacial bonding between the polymer matrix and the fibers and better dispersion of the fibers within the modified UHMWPE matrix. Chemical modification of UHMWPE before the introduction of PET fibers resulted in composites exhibiting improved wear resistance compared to the base material and compared to unmodified UHMWPE/PET composites. On the basis of the morphological studies of worn samples, microploughing and fatigue failure associated with microcracking were identified as the principle wear mechanisms. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

凹凸棒黏土纯度对复合高吸水性树脂吸水性能的影响

将凹凸棒黏土分级处理后,以不同纯度的凹凸棒黏土为无机组分,过硫酸铵为引发剂,N,N'-亚甲基双丙烯酰胺为交联剂,制备了羧甲基纤维素接枝丙烯酸/凹凸棒黏土复合高吸水性树脂,考察了复合高吸水性树脂的吸水倍率、吸水速率和在不同pH介质中的溶胀性能。红外光谱表明,丙烯酸已接枝到羧甲基纤维素的骨架上,凹凸棒黏土参与了聚合反应。扫描电镜观察表明,凹凸棒黏土在高吸水性树脂中有良好的分散性能,改善了基体表面的多孔结构。研究表明,在相同添加量下,凹凸棒黏土中含有更多的Ca2+和Mg2+离子,有助于改善复合高吸水性树脂的综合性能。     

Tribological behaviour of a 3Y-TZP/Ta ceramic-metal biocomposite against ultrahigh molecular weight polyethylene (UHMWPE)

This study aims to evaluate the tribological behaviour of 3Y-TZP/Ta (20 vol%) ceramic-metal composites and 3Y-TZP monolithic ceramic prepared by spark plasma sintering (SPS) against ultrahigh molecular weight polyethylene (UHMWPE). According to the results of pin (UHMWPE)-on-flat wear test under dry conditions, the UHMWPE – 3Y-TZP/Ta system exhibited lower volume loss and friction coefficient than the UHMWPE – monolithic ceramic combination due to the presence of an autolubricating layer that provides sufficient lubrication for reducing the friction. Owing to the lubrication of the liquid media, under wet conditions obtained using simulated body fluid (SBF), similar behaviour is observed in both cases. Additionally, the ceramic and biocomposite materials were subjected to a low temperature degradation (LTD) process (often referred to as “ageing”) to evaluate the changes in the tribological behaviour after this treatment. In this particular case, the wear properties of the UHMWPE-biocomposite system were found to be less influenced by ageing in contrast to the case of the UHMWPE-zirconia monolithic material. In addition to their exceptional mechanical performance, 3Y-TZP/Ta composites also showed high resistance to low temperature degradation and good tribological properties, making them promising candidates for biomedical applications, especially for orthopaedic implants.     

超高分子量聚乙烯纤维/有机玻璃复合材料摩擦磨损性能研究

用真空浸渍法成功制备出了超高分子量聚乙烯纤维／有机玻璃(UHMWPE／PMMA)复合材料，并对基体材料PMMA，单向超高分子量聚乙烯纤雏／有机玻璃复合材料以及三维编织超高分子量聚乙烯纤维／有机玻璃(即UHMWPE3D／PMMA)复合材料的摩擦磨损性能进行了研究。实验证明UHMWPE／PMMA复合材料具有优良的摩擦磨损性能。经过纤维增强的复合材料的摩擦磨损性能优于基体材料，三维编织纤维增强的复合材料其磨损远小于单向纤维增强的复合材料，但其摩擦系数没有显著变化。     

Hydroxyapatite/ultra-high molecular weight polyethylene nanocomposites fabricated by in situ hydrothermal synthesis for wear-resistance and friction reduction

In situ filling raises a possibility to restrain the agglomeration of nanomaterials in macromolecule matrices, which usually is encountered in the nanocomposites prepared by a mechanical mixing method. In this work, the nanocomposites of ultra-high molecular weight polyethylene (UHMWPE) filled with nanosized hydroxyapatite (HAP) were fabricated by an in situ hydrothermal method. The fabricated HAP/UHMWPE nanocomposites exhibited a high dispersion degree of HAP nanoparticles (NPs) and a marked improvement in stiffness, strength, toughness, glass-transition temperature, and hydrophilicity compared with the matrix and the reference composites prepared by mechanical mixing. Furthermore, pronouncedly decreased coefficients of friction and volume wear rates were observed on the in situ fabricated HAP/UHMWPE nanocomposites under dry friction, the lubrications of water, or cell culture fluid against a steel ring. The in situ fabricating strategy suggests a way to prepare highly dispersed nanocomposites, and the resulting HAP/UHMWPE nanocomposites might indicate a significant clinical prospect.     

Freeze‐drying method prepared UHMWPE/CNTs composites with optimized micromorphologies and improved tribological performance

Uniformly dispersed carbon nanotubes (CNTs) reinforced ultrahigh molecular weight polyethylene (UHMWPE) composites were successfully prepared by freeze‐drying method. Specifically, polymer powders were mixed with CNT aqueous paste, and then freeze‐dried. As a consequence, CNTs covered at the surface of UHMWPE powders evenly when CNT content was not very high, which improved the quantity of crystals and crystallinity of UHMWPE/CNTs composites by providing more nucleation sites during the upcoming compression‐molded process. Furthermore, optimized dispersion state of CNTs and concomitant higher crystallinity made freeze‐drying technique prepared composites display much lower wear rate when compared with pure UHMWPE and UHMWPE/CNTs composites fabricated by common heat‐drying method. In a word, our proposed method of freeze‐drying is simple and effective for mass production of UHMWPE/CNTs composites, and it is promising to be applied to fabricate many kinds of nanofillers modified polymer composites, for example, polymer/graphene material. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41885.     

UHMWPE的臭氧化降解及摩擦磨损性能研究

研究了臭氧化反应对超高摩尔质量聚乙烯（UHMWPE）熔体流动性、摩擦磨损性能以及结晶性能的影响。经臭氧化反应，UHMWPE发生降解，粘均摩尔质量从2650kg／mol降低到566kg／mol，熔体质量流动速率从0增加到0．28g／10min。随臭氧化处理时间的增加，材料摩擦系数和磨损量基本不变，UHMWPE优异的磨擦磨损性能得以保持。DSC分析结果表明，随臭氧化反应时间的增加，UHMWPE熔融焓增加，结晶度增加。     

PET/纳米凹凸棒母料复合材料性能与结构研究

制备了纳米凹凸棒母料(NAMB),并将其与聚对苯二甲酸乙二酯(PET)共混,利用X射线衍射仪、扫描电子显微镜研究了PET/NAMB复合材料的微观结构,并测试了其力学性能。结果表明,NAMB均匀分散在PET基体中呈"海-岛"结构,它的加入较大程度地提高了复合材料的缺口冲击强度,而对拉伸强度影响不大;同时提高了复合材料的结晶度。     

Ultra-high-molecular-weight polyethylene reinforced polypropylene and polyamide composites toward developing low-noise automobile interior

Circular ultra-high-molecular-weight polyethylene (UHMWPE) of 60 and 140 μm particle size, to ensure the homogenous mixing, was used as filler materials for developing the polypropylene (PP) and polyamide 6 (PA6)-based composite specimens to investigate the effect of UHMWPE on reducing the noise, if the composites are used in car interior. PP composite containing 5 wt % UHMWPE of 60 μm particle size showed the lowest in-plane friction coefficient (0.18 ± 0.01), improved Izod impact strength (33 ± 2.9 J/m²), and considerable tensile properties (37 ± 1.5 MPa of strength and 21 ± 1.1% of elongation at break), indicating its promise as low-noise and durable material to be used in the car interior. Although PA6 composites showed decreasing friction coefficients with increasing UHMWPE content, their tensile and impact properties became poor or inconsistent, maybe due to the incompatibility of nonpolar UHMWPE with polar PA, and the large difference of their melting temperatures. The extent of compatibility of PP and PA6 with the UHMWPE has been investigated by analyzing the morphology (using scanning electron microscope) and the thermal properties of the composites. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48720.     

Size effect of charcoal particles on the properties of bamboo charcoal/ultra‐high molecular weight polyethylene composites

This study was aimed at examining the size effect of charcoal particles on the properties of bamboo charcoal (BC)/ultra‐high molecular weight polyethylene (UHMWPE) composites. Four types of BC with various particle sizes were mixed with UHMWPE using a twin‐screw extruder. It was found that the melting temperature and crystallinity of the composites were slightly decreased with the addition of BC. The incorporation of BC remarkably improved the tensile properties and creep resistance of UHMWPE, and the particle size of BC strongly affected the properties of BC/UHMWPE composites. The BC with lowest particle size exhibited best reinforcement, where the tensile strength and Young's modulus were increased by 385% and 517% compared with neat UHMWPE. The composites with 70 wt % BC possessed conductivities of 16.8, 14.1, 13.5, and 10.9 S/m. The storage modulus and glass transition temperature of the composites also increased with the addition of BC. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45530.     

Study of a compatibilized ultra-high-molecular-weight polyethylene and polyurethane blend

Ultra-high-molecular-weight polyethylene (UHMWPE) and thermoplastic polyester-type polyurethane (PU) were blended with polyethylene-grafted maleic anhydride (PE-g-MAH) added as a compatibilizer. A dual roller was used as a mixer, and all specimens were produced by the compression molding method. It was found that without compatibilizer, UHMWPE and PU were immiscible polymers and mixing PE-g-MAH reduced the size of the dispersed PU domains by a factor of 10 to reach 0.5–5 μm and caused a more uniform distribution of the PU phase in the UHMWPE matrix. Also, PE-g-MAH influenced the crystallinity of UHMWPE, increased the amorphous region in the UHMWPE phase, and improved interfacial adhesion. The threshold concentration of compatibilizer was 10 wt %, and the compatibilized UHMWPE/PU composites had improved mechanical properties and lower wear rate than the uncompatibilized composite. At some ratio points, compatibilizer composites even had better wear-resistance properties than pure UHMWPE. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3290–3295, 2001