以环氧树脂为基料,氨基硅烷为固化剂,气相SiO2为分散助剂,碳化二亚胺为改性助剂,制备了不同碳纳米管含量的环氧树脂涂层。采用拉拔法测附着力,球盘磨损测耐磨性,电化学和丝状腐蚀测耐蚀性,全面评价了碳纳米管含量对环氧树脂涂层性能的影响。结果表明：碳纳米管含量为2% (质量分数) 时就能显著提高环氧树脂涂层的附着力、耐磨性和耐蚀性,同时增强涂层的导电性。当碳纳米管含量为5%和7%时,涂层的附着力和耐磨性进一步提高;当碳纳米管含量为10%时,涂层的附着力和耐磨性开始略微下降,但耐蚀性和导电性达到最佳状态。
Epoxy coatings with different mass fraction of carbon nanotube (CNT) is prepared with epoxy as matrix, amine silane as curing agent, fumed silica as disperse dispersant, and carbodiimide as modifying agent. The effect of CNT amount on properties of epoxy coating is overall evaluated by means of pull-off adhesion test, ball-on-disk ear test, electrochemical impedance spectroscopy (EIS) and filiform corrosion test. The results show that, the adhesion strength, abrasion resistance and corrosion resistance are improved remarkable for the epoxy coating with 2% (mass fraction) of CNT in comparison to that without CNT addition. All the above mentioned properties are further improved for the epoxy coating with 5% and 7% of CNT. Furthermore, when the epoxy coating with the addition of CNT is up to 10%, of which the adhesion strength and abrasion resistance decreased, while the corrosion resistance and conductivity reach the optimum.
碳纳米管由于其优异的力学性能、化学稳定性、纳米级尺度等特征,作为填料可以改善涂层的性能,其含量会对涂层的附着力、摩擦磨损和耐腐蚀等性能产生重要影响[2,3]。碳纳米管作为导电导热材料添加到涂层中,高长径比的碳纳米管在达到一定值时会相互搭接形成不规则的三维空间网络结构,从而通过碳纳米管网络导电导热,该特性符合渗流理论[4-6],通常用电学信号进行检测。根据渗流理论,当导电粒子在复合材料中达到一定含量时就能够相互接触形成导电通道,使复合材料的阻抗模值迅速降低几个数量级[7,8],该值称为渗流域值。环氧树脂涂层在固化过程中会因收缩形成微孔和内应力,从而降低涂层的致密性、力学和耐腐蚀性能。Khun等研究了含0%,0.1%,0.5% (质量分数) 的碳纳米管环氧树脂涂层的附着力、摩擦磨损和耐腐蚀性能,发现随着碳纳米管含量的增加,环氧树脂涂层的各项性能均有提高,但对更高含量碳纳米管的涂层未做进一步研究。Deyab研究了碳纳米管含量不同的聚苯胺涂层在酸性环境下的电化学性能,发现碳纳米管含量为0.8% (质量分数) 的聚苯胺涂层具有最好的耐腐蚀性能,但对更高碳纳米管含量的涂层也未做进一步研究。碳纳米管含量达到渗流阈值之后会显著提高涂层的导电性能,改善涂层的致密性,继续提高碳纳米管含量对涂层性能的影响有待进一步研究。
实验用基料为环氧硅氧烷杂化树脂,固化剂为3-氨基丙基三乙氧基硅烷,碳纳米管由深圳纳米港有限公司提供,主要参数为直径15~25 mm,长度5~15 μm,纯度>95% (质量分数) ,比表面积150~210 m2/g。
为研究碳纳米管含量对环氧树脂涂层性能的影响,配制碳纳米管含量分别为0%,2%,5%,7%和10%的5种碳纳米管环氧树脂涂料。为使氧化碳纳米管与氨基硅烷充分反应,先将碳纳米管加入到氨基硅烷中,加入一定量的碳化二亚胺促进碳纳米管和氨基硅烷反应,加入少量的二氯甲烷可以减少副产物的产生,且挥发后不影响各组分比例和性质。将碳纳米管、氨基硅烷、碳化二亚胺、二氯甲烷的混合物高速搅拌15 min,超声处理5 min,然后加入适量环氧树脂和等量的气相SiO2,再高速搅拌15 min配制成最终涂料。在配制过程中使用水浴控制涂料的温度约保持在40~60 ℃,以保证N,N-二环己基碳二亚胺为溶液状态,各组分充分反应。
氧化碳纳米管的羧基与环氧树脂的环氧基均与氨基硅烷的氨基反应,为使各组分反应完全,本文采用Boehm滴定法测定氧化碳纳米管的羧基含量。根据滴定计算,1 g碳纳米管大约会消耗0.02 g的氨基硅烷,各组涂料配比如
采用PosiTest AT-A全自动数字显示拉拔式附着力测试仪测试涂层的附着力大小,测试锭子直径20 mm,拉开有效面积大于70%。采用HT-1000型高温摩擦磨损试验机测试涂层的耐磨性能,球盘磨损实验在常温下进行,实验条件为：对磨材料钢,电机频率10 Hz,载荷200 g,摩擦半径7 mm,对磨时间10 min。采用CS350型电化学工作站测试涂层的电化学阻抗谱特性。采用HTP201E型交变湿热试验箱测试涂层的耐丝状腐蚀性能,测试环境：湿度80%,温度40 ℃。
实验选取碳纳米管含量依次为0%,2%,5%,7%和10%的环氧树脂涂层试件进行封边处理,用钢刀在各试件上同一位置划 “X”形状的刻痕,要求刻痕深度刚好划透涂层见到基底,且刻痕距离试件边缘大于10 mm。不同腐蚀时间的丝状腐蚀记录见
可见,未添加碳纳米管的环氧树脂涂层低碳钢试件在湿热环境下60 d时就发生了明显的丝状腐蚀,而添加了碳纳米管的环氧树脂涂层试件均未发生明显腐蚀,只在刻痕处生成少量腐蚀产物。到90 d时,无碳纳米管的环氧树脂涂层试件表面的丝状腐蚀显著增多增长,而添加了碳纳米管的环氧树脂涂层试件表面无明显腐蚀发生,但涂层均有不同程度的翘起脱离情况发生。使用3M600型测试胶带将湿热环境下处理90 d的各试件表面黏附剥离,结果显示,添加碳纳米管的涂层均有不同程度的剥离发生。随着碳纳米管含量的提高,涂层剥离的面积有增大的趋势,而低碳钢基底的腐蚀状态反而趋于良好。
The authors have declared that no competing interests exist.
In the present study, Ni-P-CNT composite coating was successfully fabricated via electroless plating. Scanning electron microscopy (SEM) was used to characterize the coatings. The effect of CNTs concentration in the bath on its content in the composite coatings was studied. Furthermore, the corrosion behaviour of the coatings with different contents of CNTs was evaluated using Tafel polarization and electrochemical impedance spectroscopy (EIS) methods in 3.5 wt.% NaCl aqueous solution at the room temperature. The results showed that the corrosion resistance of the Ni鈥揚-CNT composite coatings was excellent in comparison with that of the Ni-P coatings and the content of incorporated CNTs played a key role in the passivation and corrosion resistance.
The viscoelastic and mechanical properties of composites multi walled carbon nanotube (MWNT)/epoxy at different weight fractions (0.1, 0.5, 1 and 202wt.%) were evaluated by performing tensile and dynamic-mechanical thermal analysis (DMTA) tests. The MWNT/epoxy composite were fabricated by sonication and a cast molding process. The results showed that addition of nanotubes to epoxy had significant effect on the viscoelastic and mechanical properties. However, the use of 0.502wt.% increased the viscoelastic properties more significantly. Concerning viscoelastic modeling, the COLE–COLE diagram has been plotted by the results of DMTA test. These results show a good agreement between the Perez model and the viscoelastic behavior of the composite.Graphical abstractThe pulled out nanotubes and weak interfacial interaction between epoxy and nanotubes improve the damping properties.
Carbon nanotubes (CNTs) hold the promise of delivering exceptional mechanical properties and multi-functional characteristics. Ever-increasing interest in applying CNTs in many different fields has led to continued efforts to develop dispersion and functionalization techniques. To employ CNTs as effective reinforcement in polymer nanocomposites, proper dispersion and appropriate interfacial adhesion between the CNTs and polymer matrix have to be guaranteed. This paper reviews the current understanding of CNTs and CNT/polymer nanocomposites with two particular topics: (i) the principles and techniques for CNT dispersion and functionalization and (ii) the effects of CNT dispersion and functionalization on the properties of CNT/polymer nanocomposites. The fabrication techniques and potential applications of CNT/polymer nanocomposites are also highlighted.
The electrical and thermal conductivities of epoxy composites containing 0.005–0.502wt% of single-walled (SWNTs) or multi-walled (MWNTs) carbon nanotubes have been studied. The MWNT composites had an electrical percolation threshold of <0.00502wt%, whereas the thermal conductivity of the same samples increased very modestly as a function of the filler content. In the case of the SWNT composites, the electrical percolation thresholds were higher (0.05–0.2302wt%) whereas the thermal conductivity was lower than that of the pristine epoxy.
Abstract Critical factors that determine the percolation threshold of carbon nanotube (CNT)-reinforced polymer nanocomposites are studied. An improved analytical model is developed based on an interparticle distance concept. Two dispersion parameters are introduced in the model to correctly reflect the different dispersion states of CNTs in the matrix—entangled bundles and well-dispersed individual CNTs. CNT–epoxy nanocomposites with different dispersion states are fabricated from the same constituent materials by employing different processing conditions. The corresponding percolation thresholds of the nanocomposites vary over a wide range, from 0.1 to greater than 1.065wt65%, and these variations are explained in terms of dispersion parameters and aspect ratios of CNTs. Important factors that control the percolation threshold of nanocomposites are identified based on the comparison between modeling data and experimental results.
Epoxy composites based on aligned CVD-grown multi-wall carbon nanotubes with weight fractions ranging from as low as 0.001 up to 1wt% were produced. The resulting electrical properties were analysed by AC impedance spectroscopy. The composite conductivity σ follows a percolation scaling law of the form σ∝(p61pc)t with the critical mean concentration pc to form a conductive network of approximately 0.0025wt% and an exponent, t, of 1.2. The results are compared to previous studies investigating the percolation behaviour of entangled carbon nanotubes and spherical carbon black particles in the same matrix processed under similar conditions. The experimental percolation threshold for the aligned nanotubes used in this study represents the lowest threshold observed for carbon-nanotube-based polymer composites yet reported.
An investigation was conducted to find out the reason behind the failure of the powder epoxy internal coating from production flow line of Large Scale Pilot Project (LSP) from an oil exploration in Kuwait. The internal coating was completely detached and peeled out in the form of curling from the substrate, and causing the production flow line to be plugged with the deposit of paint debris. The production operation of oil supply from the LSP well was stopped due to this failure and the pipeline was replaced. Multiple field techniques and laboratory approaches were used to find out the reason behind the coating failure. The research work involved utilizing the analysis of the surface carbon steel substrate with new epoxy coated sample as compared to the failed one using differential scanning calorimetry (DSC) and optical and photomicroscope examination. The overall results indicated that the failure was due to the combined effects of the improperly cured coating as determined by differences in the glass transition temperature (Tg), and differential thermal expansion properties between the steel tube and coating causing shrinkage stresses resulting in disbonded coating. This was enhanced by the expansion of corrosion oxide products as a sequence of ineffective substrate pre-treatment.
The effects of multiwalled carbon nanotube (MWCNT) content on the adhesion strength and wear and corrosion resistance of the epoxy composite coatings prepared on aluminum alloy (AA) 2024-T3 substrates were evaluated using atomic force microscopy (AFM), blister test, ball-on-disk micro-tribological test and electrochemical impedance spectroscopy (EIS). The adhesion strength of the epoxy composite coatings improved with increasing MWCNT content. Increased MWCNT content also decreased the friction coefficient and increased the wear resistance of the epoxy composite coatings due to improved solid lubricating and rolling effects of the MWCNTs and the improved load bearing capacity of the composite coatings. Finally, EIS indicated that increased MWCNT content increased the coating pore resistance due to a decreased porosity density, which resulted in an increase in the total impedance of the coated samples.
61We examine the effect of addition of CNTs on the corrosion resistance of polyaniline in PEM fuel cell.61The addition of CNTs to polyaniline coating enhanced conductivity of polyaniline.61The addition of CNTs increases the inhibition efficiency of polyaniline coating.61Inhibition efficiency is close to 98% when CNTs concentration is 0.8%.61The techniques include electrical conductivity, polarization, EIS and SEM.
As-received multiwalled carbon nanotubes (MWCNTs) were first treated by a 3 : 1 (v/v) mixture of concentrated H2SO4/HNO3 and further functionalized by ethylenediamine/dicyclohexylcarbodiimide/tetrahydrofuran solution. MWCNT/epoxy nanocomposites were prepared. Their cure behaviors were investigated by dynamic differential scanning calorimetry. Quantitative analysis of the activation energy as a function of the degree of curing was carried out by the Flynn-Wall-Ozawa method. The fitted multiple regression equations for values of the activation energy of different systems were obtained. MWCNTs have the retardation effect on the cure reaction of epoxy resin, while the functional groups on the surface of amine-modified MWCNTs could accelerate the cure reactions. Thermal stability was studied by thermogravimetric analysis. The filling of amine-modified MWCNTs is beneficial to lower the cure activation energy and improve thermal stability of the nanocomposite. 漏 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008
Recently, an intensive research effort has been devoted to the fabrication of polymer composites with enhanced physical and chemical properties. In this work, the combination of carbon fibers (CFs) and carbon nanotubes (CNTs) was demonstrated to show a synergistic effect on improving the thermal stability and flame retardancy of polypropylene (PP). The results of morphology characterization indicated that both CFs and CNTs were well dispersed in the PP matrix. The temperature at the maximum weight loss rate of PP under an air atmosphere was dramatically increased by 93.4 掳C, and the peak value of the heat release rate measured by a cone calorimeter was significantly reduced by 71.7%. The remarkably improved thermal stability and flame retardancy of PP were partially owing to the accelerated oxidation crosslinking reaction of PP radicals by CNTs (chemical effect), and partially to thein situformation of a dense and continuous CF/CNT hybrid protective layer (physical effect). This was because the CF/CNT hybrid protective layer not only hindered the diffusion of oxygen into PP and the migration of volatile decomposition products out of PP, but also acted as a thermal shield for energy feedback from the flame.
Mechanical properties of carbon fiber (CF) and carbon nanotube (CNT)-filled thermoplastic high-density polyethylene (HDPE) composites were studied with particular interest on the effects of filler content and fiber surface treatment by coupling agent. Surface-treated CF-filled HDPE composites increased their tensile strength and impact strength, which is further increased with the addition of CNT. SEM showed that CNT-coating-treated CF-HDPE composites show better dispersion of the filler into the matrix, which results in better interfacial adhesion between the filler and the matrix. Copyright 漏 2014 John Wiley & Sons, Ltd.