β-环糊精改性的多壁碳纳米管对NO的吸附性能研究

为开发NO气敏传感器,采用β-环糊精对模板法制备的多壁碳纳米管进行了表面修饰改性.利用扫描电镜、红外光谱、X-射线衍射、热分析-质谱等表征手段研究了改性的MWCNTs的结构性能,并对NO的吸附-脱附作用机理进行了讨论.结果表明:环糊精的小口端易与多壁碳纳米管的管壁相互作用并结合在一起,使环糊精包覆在多壁碳纳米管的表面.多壁碳纳米管外或内层的环糊精可以通过氢键与环糊精以层与层的方式进行连接,达到对MWCNTs的多层改性修饰作用.XRD研究证明经环糊精改性的多壁碳纳米管其结构并没有发生变化.热分析质谱研究发现,β-环糊精改性的MWCNTs对NO的吸附-脱附能力均大于未改性的MWCNTs,其中MWCNTs吸附NO主要是表面物理吸附和管体空腔内的化学吸附;而经β-环糊精修饰的MWCNTs除本身能够吸附NO外,其表面包覆的β-环糊精空腔也能够吸附NO分子,并与NO形成非共价键吸附.β-环糊精与MWCNTs质量比为10∶1时,其吸附NO的量最大,是未改性MWCNTs的1.69倍.     

改性碳纳米管处理碳纤维的效果表征

采用浓硫酸/浓硝酸氧化处理多壁碳纳米管(MWCNTs),再将氧化后的碳纳米管与硅烷偶联剂(KH560)进行接枝,制备了硅烷偶联剂表面化学修饰的MWCNTs。在此基础上,将改性前后的碳纳米管分散在环氧树脂体系中,涂覆处理碳纤维。研究处理前后碳纤维力学性能和界面性能的变化。通过红外光谱(FTIR)和透射电镜(TEM)分析,表明KH560已成功接枝到多壁碳纳米管上;通过分散性实验证明了改性后的碳纳米管分散性提高;对处理后的碳纤维进行力学性能测试,并用扫描电镜(SEM)观察分析断面形态变化,结果表明,当碳纳米管的含量为0.5%时,改性碳纳米管处理的碳纤维拉伸强度和拉伸模量分别提高23.83%和7.11%,界面性能增强。     

多壁碳纳米管/尼龙6复合材料的液相共混法制备及其性能

通过液相共混法制备了多壁碳纳米管/尼龙6(MWCNTs/PA6)复合材料, 研究了不同MWCNTs改性方法及添加量对复合材料热性能和结晶性能的影响。利用场发射扫描电子显微镜(FESEM)、FTIR、DSC、XRD 和 TG对MWCNTs/PA6复合材料进行表征。结果表明: MWCNTs的加入提高了PA6的热稳定性, 且胺功能化的MWCNTs(d-MWCNTs)表现尤为明显; 当d-MWCNTs的质量分数为7.5%时, MWCNTs/PA6复合材料结晶度从48.09%提高到56.62%, 聚合物大分子之间的缠绕度最低。     

双亲无规共聚物修饰碳纳米管/环氧树脂复合材料的制备与性能

通过自由基聚合法制备无规共聚物聚甲基丙烯酸缩水甘油酯/N-乙烯基咔唑P(GMA-co-NVC),并将其对多壁碳纳米管(MWCNTs)进行非共价键表面修饰得到P(GMA-co-NVC)/MWCNTs,再与环氧树脂(EP)复合,采用浇注成型法制备聚合物改性碳纳米管/环氧树脂复合材料。通过拉伸实验、电阻率测试和差式扫描量热法研究聚合物改性碳纳米管对环氧树脂力学、电学和热学性能的影响。结果表明:修饰后的碳纳米管比原始碳纳米管对环氧树脂有更明显的增强和增韧作用,当P(GMA-co-NVC)/MWCNTs质量分数为0.25%时,复合材料的体积电阻率为106Ω·m,相比于纯环氧树脂(1014Ω·m)下降了8个数量级,玻璃化转变温度(Tg)也由144℃提高至149℃。     

两亲性嵌段共聚物改性的多壁碳纳米管的制备

通过对碳纳米管进行表面改性制得具有引发ATRP反应活性的碳纳米管(MWNT-Br),以MWNT-Br作引发剂经过两次ATRP反应将聚乙烯基吡咯烷酮(PVP)和聚甲基丙烯酸特丁酯(PtBMA)先后接枝到多壁碳纳米管表面制得两亲性嵌段共聚物接枝的碳纳米管(MWNT-PVP-b-PtBMA),用红外光谱、热失重和透射电镜对两亲性碳纳米管进行了表征.并考察了修饰前弱亲油性的纯碳纳米管、酸化后亲水性的碳纳米管和修饰后两亲性碳纳米管这3种碳纳米管在水和氯仿形成的两相体系中的分散情况,观察到所制备的两亲性碳纳米管能够均匀分散在油水两相界面上.     

聚对苯二甲酸乙二醇酯共价接枝多壁碳纳米管及其表征

通过两步法将聚对苯二甲酸乙二醇酯(PET)分子链共价接枝到多壁碳纳米管(MWCNTs)表面,成功地制备了PET/MWCNTs复合材料。聚丙烯酰氯共价接枝MWCNTs的表面具有多个可反应的酰氯基团,通过与PET端羟基间的反应,以聚丙烯酰氯为中间聚合物层,成功将PET分子链接枝到了碳纳米管表面。采用傅立叶变化红外光谱(FT-IR)、透射电镜(TEM)、核磁(1H-NMR)和热失重分析(TGA)对接枝产物进行了表征,结果表明,PET分子已通过共价接枝的方式接枝到碳纳米管表面,被接枝聚合物的量约为MWCNTs的96%,该接枝聚合物层的存在将有利于多壁碳纳米管与PET树脂间相容性的提高,从而使PET/MWCNTs复合材料的性能得到提高。     

多壁碳纳米管功能化及其增韧环氧树脂的研究

采用混酸氧化多壁碳纳米管(MWCNTs),然后将其与过氧化丁二酸反应,接着对其进行酰胺功能化处理,并用功能化后的MWCNTs对环氧树脂(EP)进行增韧改性,研究了不同含量MWCNTs对EP力学性能的影响,探讨了其改性机理.研究结果表明,经过功能化处理,MWCNTs表面成功接上了一定数量的酰胺基团,将其加入到EP中可大幅度提高EP的冲击强度,在其用量为1.5wt%时,冲击强度提高了92%;SEM结果显示,加入MWCNTs后EP由脆性断裂转变为韧性断裂.     

碳纳米管表面改性对碳纳米管/尼龙66复合材料机械性能影响的研究

采用熔融共混法,在尼龙66基体中分别加入不同改性的多壁碳纳米管(MWCNTs)制备MWCNTs/尼龙66复合材料。考察MWCNTs改性方法对MWCNTs结构,以及不同改性MWCNTs对复合材料形貌和机械性能的影响。研究发现:通过酸化-氨化过程,在MWCNTs表面引入了酰胺基团;FESEM显示,胺化碳纳米管(D-MWCNTs)分散均匀于尼龙66基体中;随着D-MWCNTs的引入,与纯尼龙66相比,D-MWCNTs/尼龙66复合材料的拉伸强度和拉伸模量分别增加了12.7%和24.3%;储能模量,在玻璃化区域(-40℃)和橡胶区域(120℃),分别较纯尼龙66提高了133.1%和73.3%。这些研究结果证明,MWCNTs的均匀分散,有利于提高聚合物复合材料的机械性能。     

功能化多壁碳纳米管负载铁离子改性双极膜的制备与表征

分别用未功能化的多壁碳纳米管(MWCNTs)、羟基化多壁碳纳米管(MWCNTs-OH)、羧基化多壁碳纳米管(MWCNTs-COOH)、磺酸基化多壁碳纳米管(MWCNTs-SO3H)改性羧甲基纤维素钠(CMC)-聚乙烯醇(PVA)/壳聚糖(CS)-聚乙烯醇双极膜(BPM)的阳离子交换膜层。采用力学性能分析、接触角测定、电流密度-槽电压曲线等对改性前后双极膜的性能进行表征,并测定了改性前后双极膜中Fe~(3+)的流失量。结果表明,经功能化多壁碳纳米管改性后,双极膜的亲水性和力学性能得到了显著提高。功能化多壁碳纳米管和Fe~(3+)对催化中间界面层水解离有协同作用,大大提高了中间界面层水解离效率,降低了双极膜的膜阻抗和槽电压。此外,改性后双极膜中Fe~(3+)的流失量有了明显的下降,从而保持了双极膜结构和催化水解离性能的稳定性。     

高能量超声波改性MWCNTs/环氧树脂特性分析

采用高能量超声波与低能量超声波对一种多壁碳纳米管(MWCNTs)/环氧树脂体系进行改性处理,结合流变仪、DSC、FTIR、XPS、XRD、TEM等测试手段,分析了不同超声波处理条件下MWCNTs物理化学特性的变化及其对MWCNTs在环氧树脂中的分散性和相容性的影响,并进一步考察了MWCNTs/环氧树脂体系的耐热性和弯曲性能。实验结果表明:超声波能量不同,MWCNTs的改性效果不同,高能量超声波对MWCNTs有更好的分散效果和分散效率,并能使MWCNTs表面活性增强,而低能量超声波则不明显;添加少量高能量超声波改性的MWCNTs,可以提高环氧树脂的弯曲模量和玻璃化转变温度,表明MWCNTs与基体之间形成了较强的结合界面。     

Effect of SiC coated MWCNTs on the thermal and mechanical properties of PEI/LCP blend

Multiwalled carbon nanotubes (MWCNTs) were modified by polycarbosilane derived β-SiC particle to improve its dispersion in the polymer matrix. Formation of β-SiC particle onto MWCNTs was conformed by XRD study. Polyetherimide (PEI)/liquid crystalline polymer (LCP) blends with unmodified and modified MWCNTs were prepared by melt blending and the dispersion of the nanofillers in the polymer blend was studied by high resolution transmission electron microscopy, which showed improved dispersion of modified MWCNTs compared to pure MWCNTs. Viscosity of ternary blend with modified MWCNTs was found to be lower than the ternary blend with pure MWCNTs. Incorporation of modified MWCNTs improved the fibrillation of LCP in ternary blend as compared to pure MWCNTs. Thermal analysis revealed the higher thermal stability of the modified MWCNTs added nanocomposites compared to unmodified MWCNTs. Mechanical properties of nanocomposites with SiC coated MWCNTs were found to be higher than that of pure MWCNTs added nanocomposites.     

Fire structural modelling of fibre–polymer laminates protected with an intumescent coating

This paper presents a new modelling approach to analyse the fire structural response of fibre–polymer laminates protected with an intumescent surface coating. The model is designed to predict the temperature, decomposition, softening and failure of laminates with an intumescent coating in fire. The modelling involves a three-stage analytical approach: (i) thermal-chemical analysis of the intumescent coating, (ii) thermal-chemical analysis of heat transfer through the laminate substrate (beneath the intumescent coating), and (iii) thermal-mechanical analysis of the softening and failure of the laminate under tension or compression loading. Fire structural tests were performed on a woven glass/vinyl ester laminate coated with an organic intumescent material to validate the modelling approach. It is shown the model can predict with good accuracy the temperature distribution and swelling of the intumescent coating with increasing exposure time to a constant heat flux. The model can approximate the temperature, softening and failure of the laminate substrate.     

Effect of polyphosphazene and modified carbon nanotubes on the morphological and thermo-mechanical properties of polyphenylene sulfide and liquid crystalline polymer blend system

Ternary blends of polyphenylene sulfide (PPS) and liquid crystalline polymer (LCP) with either polyphosphazene, unmodified multiwall carbon nanotubes (MWCNTs) or SiC-coated MWCNTs, were prepared by melt blending. While polyphosphazene improved the compatibility between the PPS and LCP, unmodified MWCNTs promoted LCP domain deformation, from spherical to ellipsoidal. Long LCP fibers were formed in presence of SiC-coated MWCNTs due to the bridging effect of modified MWCNTs at the interface of PPS and LCP. This bridging effect was confirmed by field emission scanning electron microscopy (FESEM). The better dispersion of SiC-coated MWCNTs was confirmed by both FESEM and transmission electron microscopy analysis. The superior mechanical properties of SiC-coated MWCNTs added blend system can be attributed to the fibrillation of LCP and better dispersion of SiC-coated MWCNTs. Polyphosphazene containing blend system showed lowest thermal stability while blend with SiC-coated MWCNTs was found to be highest, among all the blend systems.     

MWCNTs表面改性剑麻纤维及其环氧树脂基复合材料传感器的制备及性能

通过引入多功能化纳米颗粒从而赋予天然纤维增强高分子复合材料多功能性,使其具有传感性能,可原位感应外界环境变化。但制备多功能纳米复合材料通常需预先将纳米颗粒均匀分散在基体中,造成基体粘度大,难以工程化应用,同时需使用较大添加量才能达到渗透阈值。采用"染布法"以多壁碳纳米管(MWCNTs)悬浮液为"染料"对剑麻纤维(SF)表面进行改性,制备了多功能的剑麻纤维(MWCNTs-SF)及其环氧树脂基复合材料(MWCNTs-SF/EP)传感器。改性后剑麻纤维表面形成了一层连续的MWCNTs涂层。MWCNTs-SF的伏安特性曲线显示MWCNTs-MWCNTs和MWCNTs-电极之间形成了欧姆接触。MWCNTs-SF及MWCNTs-SF/EP均为负温度系数热敏电阻。在外界应力-应变的作用下,MWCNTs-SF及MWCNTs-SF/EP的电阻起初没有明显的变化,然后随应变线性增加,接着与应变成指数关系。MWCNTs-SF及MWCNTs-SF/EP对温度与应力-应变的响应特性不同是由于复合材料成型过程中的MWCNTs网络结构发生了变化。同时,随着MWCNTs改性次数增加,剑麻纤维布增强环氧树脂基复合材料的拉伸强度逐渐从37.6 MPa增大到46.7 MPa,弹性模量也相应增大。     

Effect of modified MWCNT on the properties of PPO/LCP blend

In this work we have coated multiwalled carbon nanotubes (MWCNTs) with SiC by solgel process and these modified MWCNTs are dispersed in PPO/LCP blend. The dispersion of these modified MWCNTs are analyzed by FESEM and found to be improved compared to pure MWCNTs. Thermal and mechanical properties of the modified MWCNTs added nanocomposites are higher than that of the pure MWCNTs added nanocomposites. PPO/LCP forms an incompatible blend while addition of unmodified and modified MWCNTs improves the compatibility between the blend partners.     

Novel approach for the selective dispersion of MWCNTs in the Nylon/SAN blend system

Multiwalled carbon nanotubes (MWCNTs) were coated with TiO₂ by sol gel process. The coating was confirmed by TEM, XPS and XRD. TEM analysis showed that rough coating was formed on the MWCNTs. These modified MWCNTs and pristine MWCNTs were dispersed in the blend of nylon 66 and SAN by melt blending. FESEM images showed that pristine MWCNTs were preferably dispersed in the nylon phase whereas TiO₂ modified MWCNTs confined to the SAN phase. The selective dispersion was explained on the basis of migration and stabilization of these high aspect ratio nanotubes in the Nylon/SAN blend system. The hydrogen bonding interaction between the CN group of SAN and surface hydroxyl group of TiO₂ coated MWCNTs has restricted the migration of modified MWCNTs from SAN to nylon phase.     

Thermal conductivity of polymer composites based on the length of multi-walled carbon nanotubes

The anisotropic development of thermal conductivity in polymer composites was evaluated by measuring the isotropic, in-plane and through-plane thermal conductivities of composites containing length-adjusted short and long multi-walled CNTs (MWCNTs). The thermal conductivities of the composites were relatively low irrespective of the MWCNT length due to their high contact resistance and high interfacial resistance to polymer resins, considering the high thermal conductivity of MWCNTs. The isotropic and in-plane thermal conductivities of long-MWCNT-based composites were higher than those of short-MWCNT-based ones and the trend can accurately be calculated using the modified Mori-Tanaka theory. The in-plane thermal conductivity of composites with 2 wt% long MWCNTs was increased to 1.27 W/m·K. The length of MWCNTs in polymer composites is an important physical factor in determining the anisotropic thermal conductivity and must be considered for theoretical simulations. The thermal conductivity of MWCNT polymer composites can be effectively controlled in the processing direction by adjusting the length of the MWCNT filler.     

Improved the electrochemical property of multiwall carbon nanotubes by mesophase pitch fluoride coating

The surfaces of two types of multiple wall carbon nanotubes (MWCNTs), namely, straight and distorted tubes, were modified by mesophase pitch fluoride coating (PFC). Brunauer–Emmett–Teller analysis, X-ray photoelectron spectroscopy, and transmission electron microscopy were used to compare the specific surface area (SSA), functional groups, and micrograph of the MWCNTs with and without modified coating. Results show that PFC can improve the SSA of the straight tube (55 %) more significantly than that of the distorted tube (7.27 %). However, surface coating is more easily implemented on the latter (F/C = 0.48) than on the former (F/C = 0.44) because of self-structure features. Electrochemical measurements indicate that PFC may enhance the specific surface capacitance and energy density of the two MWCNTs because of the effect of functional groups on the modified surface.     

Thermal–mechanical modelling of laminates with fire protection coating

This paper presents a modelling approach to analyse the protection provided by passive and intumescent surface coatings on glass fibre reinforced laminate substrates exposed to fire. The modelling involves a multi-stage analytical approach: (i) thermal analysis of heat transfer from the fire through the surface insulation coating, which includes decomposition and expansion in the case of an intumescent material; (ii) thermal–chemical analysis of heat transfer through the fibreglass laminate substrate (beneath the fire protective coating), including decomposition of the polymer matrix; and (iii) thermal–mechanical analysis of softening and failure of the laminate under in-plane tension or compression loading. The modelling approach is validated using experimental temperature and strength data from fire structural tests performed on woven glass–vinyl ester laminates insulated with passive (ceramic fibre mat) or organic intumescent surface coatings.     

The role of functionalized carbon nanotubes in a PA6/LCP blend

Multi-walled carbon nanotubes (MWCNTs) were carboxyl-functionalized in order to improve their dispersion in a polymer matrix. The carboxyl-functionalized MWCNTs (i.e., MWCNT-COOH) were added into a blend matrix consisting of polyamide 6 (PA6) and liquid crystalline polymer (LCP) (PA6:LCP = 80:20 in weight) to make ternary composites. The effects of MWCNT-COOH on the rheological, physical, morphological, thermal, mechanical, and electrical properties of the ternary composites have been examined systematically. The dispersion of MWCNTs in the polymer matrix and their interactions with the polymers (i.e., PA6 and LCP) were found to be the most important factors affecting all properties. The functionalization of MWCNTs resulted in the significant improvement in their dispersion in the polymer matrix and largely enhanced the interactions of MWCNTs with the polymer matrix. The functionalized MWCNTs acted not only as reinforcement fillers but also as a compatibilizer that could enhance the interfacial adhesion between PA6 and LCP. Interestingly, the packing density of the polymer matrix was greatly increased by adding MWCNT-COOH.