Friction and wear of epoxy/TiO2 nanocomposites: Influence of additional short carbon fibers, Aramid and PTFE particles

An epoxy-based nanocomposite containing graphite powder (7 vol%) and nano-scale TiO₂ (4 vol%) was developed for tribological evaluation. A series of composites containing additional fillers such as short carbon fibers (SCF), Aramid and polytetrafluoroethylene (PTFE) particles was developed and evaluated in adhesive and low amplitude oscillating wear modes. The incorporation of SCF and Aramid particles resulted in a remarkable improvement in the sliding wear resistance. However, SCF impaired the low amplitude oscillating wear resistance. The further addition of PTFE to the SCF filled nanocomposites reduced the friction and wear under both wear conditions. However, an adverse effect of PTFE was found for the Aramid particles filled nanocomposites. Under sliding conditions, the lowest wear rate and coefficient of friction showed the 2–4 vol% PTFE filled SCF nanocomposite. Aramid particles containing nanocomposites (without PTFE) exhibited the best wear and friction behavior under low amplitude oscillating wear conditions among the selected composites. The wear mechanisms were studied by scanning electron microscopy.     

Friction and wear studies of polyimide composites filled with short carbon fibers and graphite and micro SiO2

Polyimide (PI) composites filled with short carbon fibers (SCFs), micro SiO₂, and graphite (Gr) particles were prepared by means of hot press molding technique. The friction and wear properties of the resulting composites sliding against GCr15 steel were investigated on a model ring-on-block test rig. Experimental results revealed that single incorporation of graphite and SCF significantly improve the tribological properties of the PI composites, but micro SiO₂ was harmful to the improvement of the friction and wear behavior of the PI composite. It is found that a combinative addition of Gr, SCF and micro SiO₂ was the most effective in improving the friction-reducing and anti-wear abilities of the PI composites. Research results also show that the filled PI composites exhibited better tribological properties under higher PV-product.     

碳纤维和二硫化钼混杂增强尼龙复合材料的摩擦学性能研究

以注塑成型法制备MoS₂和碳纤维混杂增强尼龙1010复合材料,采用MM-200型磨损试验机考察复合材料摩擦磨损性能。研究结果表明:在干摩擦条件下,MoS₂和碳纤维混杂可显著改善尼龙复合材料摩擦学性能,较小载荷下复合材料磨损以轻微磨粒磨损和疲劳磨损为主,较高载荷下复合材料则以热疲劳断裂剥落磨损为主。摩擦过程中MoS₂和对偶铁发生摩擦化学反应,生成和对偶底材具有较强结合能力的硫化亚铁和硫酸铁等,同时部分被氧化生成MoO₃。     

Role of zirconia filler on friction and dry sliding wear behaviour of bismaleimide nanocomposites

This paper discusses the friction and dry sliding wear behaviour of nano-zirconia (nano-ZrO₂) filled bismleimide (BMI) composites. Nano-ZrO₂ filled BMI composites, containing 0.5, 1, 5 and 10 wt.% were prepared using high shear mixer. The influence of these particles on the microhardness, friction and dry sliding wear behaviour were measured with microhardness tester and pin-on-disc wear apparatus. The experimental results indicated that the frictional coefficient and specific wear rate of BMI can be reduced at rather low concentration of nano-ZrO₂. The lowest specific wear rate of 4 × 10⁻⁶ mm³/Nm was observed for 5 wt.% nano-ZrO₂ filled composite which is decreased by 78% as compared to the neat BMI. The incorporation of nano-ZrO₂ particles leads to an increased hardness of BMI and wear performance of the composites shows good correlation with the hardness up to 5 wt.% of filler loading. The results have been supplemented with scanning electron micrographs to help understand the possible wear mechanisms.     

Influence of functional graphene as filler on the tribological behaviors of Nomex fabric/phenolic composite

Graphene and polystyrene functionalized graphene (PS-graphene) had been synthesized, and were employed as fillers to improve the anti-wear property and load-carrying capacity of Nomex fabric/phenolic composites. Pin-on-disk type wear tests show that the friction coefficients and wear rates for both graphene and PS-graphene filled fabric/phenolic composites were reduced, when compared with unfilled fabric composite. Moreover, it was found that the 2 wt% PS-graphene filled Nomex fabric/phenolic composites exhibited the optimal tribological properties. The enhancement on the wear property of graphene and PS-graphene filled Nomex fabric composite was mainly due to the self-lubrication of graphene and the easy-formed transfer film on the counterpart pin. We also investigated the effect of filler content, applied load, and sliding speed on the tribological properties of the Nomex fabric/phenolic composites.     

Effect of sequence of nanoclay addition in TPU/PP blends: thermomechanical properties

Nanoclay filled thermoplastic polyurethane (TPU)/polypropylene (PP) blends compatibilized with maleic anhydride grafted polypropylene (MA-g-PP) have been studied with emphasis on sequence of nanoclay addition. In sequence I [TPU(nano)/PP/MA-g-PP], nanoclay was first added to TPU and this nano composite was blended with PP, using MA-g-PP as compatibilizer. In the case of sequence II [TPU/PP(nano)/MA-g-PP], nanoclay was added first to PP and blended with TPU, using MA-g-PP as compatibilizer. These blend systems were evaluated by DSC, FTIR, DMA, SEM, XRD and tensile properties. The results indicated that sequence I imparted greater compatibility to the polymers and better nanoclay dispersion than sequence II. Overall the TPU(nano)/PP/MA-g-PP blend system shows better dispersion than TPU/PP(nano)/MA-g-PP.     

Optimization of reinforcement content and sliding distance for AlSi7Mg/SiCp composites using response surface methodology

Extruded AlSi7 Mg alloy based SiC_p reinforced (AlSi7 Mg/SiC_p) composites and the matrix alloy were wear tested on a pin on disk type tester. The work was planned so that some response surface (RS) models can be used to examine the wear behaviour of composite samples. The effects of friction load, sliding distance and reinforcement content on the wear rate and weight loss of AlSi7 Mg/SiC_p composites were evaluated by using RS optimization procedure. In the applications of RS models to engineering problems, the estimated RS models usually have a maximum or a minimum point. Through this article the RS optimization procedure was employed to optimize the reinforcement content and sliding distance for the minimization of wear rate and weight loss of tested composites. During the tests, the values of reinforcement content, friction load and sliding distance were changed on the intervals (0%, 20%), (49 N, 169 N), (100 m, 1000 m), respectively. It was shown that there exists some optimum values of reinforcement content and some optimum values of sliding distance which minimize the wear rates also weight losses of tested composites for some fixed values of friction load in the experimental region. In this concern, the average value of optimum reinforcement contents and the average value of optimum sliding distances of AlSi7 Mg/SiC_p composites minimizing the wear rate were found as 13% and 595 m, respectively. Also the average value of optimum reinforcement content minimizing the weight loss was found as 13%.     

Abrasive wear behaviour of hard powders filled glass fabric–epoxy hybrid composites

The effect of incorporation of tungsten carbide (WC) and tantalum niobium carbide (Ta/NbC) powders on three-body abrasive wear behaviour in glass fabric–epoxy (G–E) composites was investigated and findings are analysed. A vacuum assisted resin transfer moulding (VARTM) technique was employed to obtain a series of G–E composites containing different fillers (WC and WC + Ta/NbC). Dry sand rubber wheel abrasion test was carried out at 200 rpm speed. The effect of different loads (22 and 32 N) and abrading distances (from 135 to 540 m) on the performance of the wear resistance were measured. The wear volume loss of the composites was found increasing with the increase in abrading distances and under the same conditions the specific wear rate decreases. The hard powders filled G–E composite systems exhibit lower wear volume loss and lower specific wear rate as compared to unfilled G–E composite system. The features of worn surfaces of the specimen were evaluated at higher and lower abrading distances at load of 32 N were using scanning electron microscope (SEM) and results indicate more severe damage to matrix and glass fiber in unfilled composite system as compared to hard powder filled composites.     

Study of the effective parameters on mechanical and electrical properties of carbon black filled PP/PA6 microfibrillar composites

In this study the electrical and mechanical properties of microfibrillar polypropylene (PP)/polyamide6 (PA6) blend filled with super conductive carbon black (CB) have been investigated. In situ microfibrillar PP/PA6 composites filled with CB are produced using a single screw extruder equipped with a spinneret. Glycidyl methacrylate (GMA) grafted polypropylene (PP-g-GMA) is used as the compatibilizer. To investigate the effects of extensional flow on the microstructure, electrical and mechanical properties, three adaptors with various convergence angles were designed, prepared and applied between the extruder and the spinneret. To optimize the effects of processing and material parameters on the electrical and mechanical properties, the Taguchi method of experimental design is used. Material and processing factors which are studied include: concentration of PA6, compatibilizer level, CB concentration, drawing speed of melt spinning line, adaptor angle, order of mixing and temperature profile along the extruder. The results show an increase in DC conductivity of up to 10¹¹ times in comparison with pure PA6, by increasing the concentration of CB, drawing speed, adaptor angle and optimizing other parameters. By optimizing processing and material factors studied here, strength of microfibrillar structured composites is increased of up to 80% in comparison to pure PP.     

纳米SiO2填充短炭纤维/环氧复合材料的摩擦磨损性能

研究了纳米SiO2填充短炭纤维/环氧复合材料的摩擦磨损性能。为了提高纳米粒子的分散性,对其进行了表面接枝改性。用磨损试验机评价了复合材料的摩擦学性能,发现当纳米粒子质量分数为5%,纤维质量分数为10%时,复合材料具有最低的摩擦系数和比磨损率。用扫描电镜观察了磨损面的形貌,研究了各种材料在相同条件下被硝酸刻蚀的程度,并用...     

Tribological properties of surface modified nano-alumina/epoxy composites

Nano-sized Al₂O₃ particles grafted with polystyrene or polyarcrylamide were employed as fillers for fabricating epoxy based composites. Curing habit, mechanical properties and tribological performance revealed by sliding wear tests of the composites were investigated. The experimental results indicated that the nanoparticles accelerate curing of epoxy, increase composites' impact strength and decrease wear rate and frictional coefficient of the composites. The surface modification by means of grafting polymerization can further enhance the properties improvement of epoxy due to the increased filler/matrix interfacial interaction. Compared to frictional coefficient, wear rate of epoxy can be decreased more remarkably by the addition of nano-alumina when rubbing against steel. The wear mode changes from severe peeling off of unfilled epoxy to mild micro-ploughing in the case of nano-alumina filled composites.     

Development, structure and strength properties of PP/PMMA/FA blends

A new type of flyash filled PP/PMMA blend has been developed. Structural and thermal properties of flyash (FA) filled polypropylene (PP)/polymethyl methacrylate (PMMA) blend system have been determined and analysed. Filled polymer blends were developed on a single screw extruder. Strength and thermal properties of FA filled and unfilled PP/PMMA blends were determined. Addition of flyash imparted dimensional and thermal stability, which has been observed in scanning electron micrographs and in TGA plot. Increase of flyash concentration increased the initial degradation temperature of PP/PMMA blend. The increase of thermal stability has been explained based on increased mechanical interlocking of PP/PMMA chains inside the hollow structure of flyash.     

Compatibilizing effect of mesoporous fillers on the mechanical properties and morphology of polypropylene and polystyrene blend

Polypropylene(PP)/Polystyrene(PS) (PP/PS = 80/20) blend with different types of fillers were prepared by using melt method. Four different types of fillers, namely mesoporous MCM-41 (without template), nano-SiO₂, Polymethylmethacrylate (PMMA)/MCM-41 and PMMA/SiO₂ were considered. For PMMA/MCM-41 filler, the synthesis of the filler consisting of entrapped strand of PMMA within the pores of mesoporous MCM-41 (without template) was described. The mechanical properties of the blend determined as the nano-fillers contents and the different types of blend were found to vary with the different interface between fillers and the matrix. SEM revealed a good interaction between the matrix phases and PMMA/MCM-41 or MCM-41 (without template). The decreased T_g of PS implied that the good adhesion between PP and PS blend was obtained by adding PMMA/MCM-41 nano-filler.     

Synergy in carbon black-filled natural rubber nanocomposites. Part I: Mechanical,dynamic mechanical properties,and morphology

Synergistic effect of carbon black (CB) in presence of nanofillers (nanoclay and nanofiber) on mechanical and dynamic mechanical properties was discussed in light of electrostatic interactions and the concomitant microstructural developments, in Part I of this series. These interactions enhanced filler dispersion and ensured efficient stress transfer from the matrix resulting in improvement in properties, undiminished even by continual increase in CB loading. In this part, the micromechanical processes that influence wear behavior have been addressed conjointly with dynamic mechanical properties. Tribological characteristics were studied by sliding rubber wheel samples against a steel blade, in a specially designed abrader, in both transient and steady state conditions. Wear loss was reduced in the dual filler nanocomposites by 33% (over the CB microcomposite) in less stringent and 75% under severe wear conditions. These CB filled nanocomposites also illustrated lowering of coefficient of friction and temperature build-up. This was attributed to efficient heat dissipation due to the formation of a unique microstructural architecture by the participating fillers and also an adhering transfer film on the abraders’ counterface. From viscoelastic measurements, the CB filled nanocomposites were also found to lie in the high performance window of good wet skid and low rolling resistance.     

Fracture toughness and failure mechanisms in unreinforced and long-glass-fibre-reinforced PA66/PP blends

In this paper unreinforced and long-glass-fibre-reinforced PA66/PP blends with different glass-fibre sizing were studied with respect to their fracture toughness determined by the typical K_c method. The fracture surfaces of these blends were studied by scanning electron microscopy in order to characterize the failure mechanisms. For the unreinforced blends a decrease in fracture toughness was observed when 25 wt% of polyamide (PA) was added to the polypropylene (PP) matrix, compared with the plain PP and PA matrices. On the other hand an increase in fracture toughness was observed when 25 wt% of PP was added to the PA matrix. This was explained by the differences in thermal expansion of PP and PA. The fracture toughness of the long-glass-fibre (LGF) composites were not affected by the glass-fibre sizing up to a PA/PP ratio of 50/50. After the phase inversion from a continuous PP to a continuous PA phase in the matrix (between PA/PP ratios of 50/50 and 75/25) the PA glass-fibre sized composite showed higher fracture toughness than the PP sized. This was explained by the change of the fibre-related failure mechanism from frequent fibre pull-out to fibre fracture. In addition the matrix affected the fracture toughness of the PA/PP75/25 blend with PA glass-fibre sizing in a positive way, resulting in the highest fracture toughness observed in this study.     

纳米ZnO和SiO2共混填充UHMWPE复合材料的摩擦磨损行为

以纳米ZnO和纳米SiO2作为复合填料,通过热压成型工艺制备了纳米ZnO-SiO2复合填充超高分子量聚乙烯(UHMWPE)复合材料;采用销-盘式摩擦磨损试验机考察了复合材料在干摩擦条件下与45#钢配副时的摩擦磨损行为;采用扫描电子显微镜观察了复合材料磨损表面形貌。结果表明,适量的纳米ZnO-SiO2作为复合填料可有效地改善UHMWPE的摩擦磨损性能,其中填充2%ZnO 2%SiO2的UHMWPE基复合材料改性效果最为明显。与纯UHMWPE材料相比,其磨损率下降了84.7%。纯UHMWPE的磨损机制主要表现为粘着磨损和疲劳磨损,而不同含量的无机纳米微粒共混填充UHMWPE基复合材料的磨损机制主要表现为不同程度的粘着磨损、犁沟效应和塑性变形特征。     

Impact of carbon black substitution with nanoclay on microstructure and tribological properties of ternary elastomeric composites

Various particulate composites based on epoxidised natural rubber (ENR), carbon black (CB), and nanoclay (NC) were prepared keeping the total filler content constant at 35 phr (parts per 100 g rubber). Tribology and hysteretic (stress–strain) properties of the composites were analyzed. Morphology of these composites were also characterized by small angle X-ray scattering (SAXS), transmission electron microscopy (TEM), scanning electron microscopy (SEM) to establish the structure–property correlations. SAXS results reveal enhancement in overall interfacial roughness (ds) with the increased substitution of CB by NC. Increased CB–NC interface causes enhancement in ds, leading to reduction in wear resistance of ternary composites. Reduction of wear resistance for NC populated samples is attributed to lower dispersion parameter (D_0,1) values of NC in the matrix, realized through image analysis of TEM photomicrographs. Thus, for ternary particulate samples, a definite interrelation among the extent of wear, ds and D_0,1 is realized. Frictional force (F_T) and its adhesive component (F_A) increase when CB is substituted by NC up to 15 phr. When NC fraction exceeds 15 phr, both F_T and F_A decrease substantially. This is attributed to the lubricity offered by the modified NC at higher NC concentration, which is explained using a predictive mechanism.     

Optimization of tribological parameters in abrasive wear mode of carbon-epoxy hybrid composites

Abrasive wear performance of fabric reinforced composites filled with functional fillers is influenced by the properties of the constituents. This work is focused on identifying the factors such as filler type, filler loading, grit size of SiC paper, normal applied load and sliding distance on two-body abrasive wear behaviour of the hybrid composites. Abrasive wear tests were carried on carbon fabric reinforced epoxy composite (C-E) filled with filler alumina (Al₂O₃) and molybdenum disulphide (MoS₂) separately in different proportions, using pin-on-disc apparatus. The experiments were planned according to Taguchi L18 orthogonal array by considering five factors, one at two levels and the remaining at three levels, affecting the abrasion process. Grey relational analysis (GRA) was employed to optimize the tribological parameters having multiple-response. Analysis of variance (ANOVA) was employed to determine the significance of factors influencing wear. Also, the comparative specific wear rates of all the composites under dry sliding and two-body abrasive wear were discussed. The analysis showed that the filler loading, grit size and filler type are the most significant factors in controlling the specific wear rate of the C-E composite. Optimal combination of the process parameters for multi performance characteristics of the composite under study is the set with filler type as MoS₂, filler loading of 10 wt.%, grit size 320, load of 15 N and sliding distance of 30 m. Further, the optimal parameter setting for minimum specific wear rate, coefficient of friction and maximum hardness were corroborated with the help of scanning electron micrographs.     

Study on the synergistic effect of carbon fiber and graphite and nanoparticle on the friction and wear behavior of polyimide composites

In this paper, the effect of short carbon fiber (SCF), graphite (Gr) and nano-Si₃N₄ on the friction and wear behavior of polyimide (PI) composites were studied using a block-on-ring arrangement. Experimental results revealed that single incorporation of SCF and Gr can improve the friction-reducing and anti-wear abilities of the PI composites significantly. However, nano-Si₃N₄ deteriorated the wear resistance of the PI composite drastically as single filler. A synergistic effect was found for the combination of nano-Si₃N₄ and SCF and Gr, which lead to the best tribological properties. It also can be found that the filled PI composites exhibited better tribological properties under higher PV product (the product of load and sliding speed). Moreover, the filled PI composites showed better tribological properties under oil lubrication and worse tribological properties under water lubrication compared with that under dry sliding condition.