Mechanical properties of electrospun PVA/MWNTs composite nanofibers

Composites of polyvinyl alcohol (PVA) and multi-walled carbon nanotubes (MWNTs) were prepared by electrospinning. A PVA/MWNTs solution was electrostatically spun to form filler wrapped nanofibers, with a diameter of ∼ 100-200 nm. As the concentration of filler in the composite was varied, the coloration of the fiber sheets changed. The SEM and TEM analyses of the fiber sheets revealed that the deformation of the fiber increases with increasing nanotube concentration. The mechanical properties were studied using a universal testing machine (UTM). The analysis is presented in detail. It is argued that the degree of dispersivity orientation and anisotropy of the nanotubes and the amount of interfacial stress in the filler/polymer are the predominant factors determining the variation in the tensile properties of the composites with the filler concentration.     

混杂功能化碳纳米管/聚氨酯复合材料的制备及性能

以多壁碳纳米管（MWNTs）为原料,采用不同改性方法制得了羧化碳纳米管（MWNTs-COOH）、共价功能化碳纳米管（MWNTs-NH₂）、非共价功能化碳纳米管（MWNTs-PPA）和混杂功能化碳纳米管（MWNTs-COOH-PPA）,将这4种改性碳纳米管按不同质量分数分别加入聚氨酯（PU）中制备了复合材料。使用万能材料试验机和热失重分析仪测试了复合材料的力学和热学性能,研究了碳纳米管对复合材料性能的影响。结果表明:通过在碳纳米管表面接枝少量的共价官能团防止非共价包覆的剥离,混杂功能化方法既能够改善碳纳米管在基体中的分散性,又能够保持其与基体界面间结合力,复合材料增强效果最明显。耐热性良好的碳纳米管的添加提高了PU基体的热分解温度,提高程度由于其功能化方式的不同而稍有差别。MWNTs-COOH-PPA/PU复合材料的力学性能最优,当碳纳米管含量（质量分数,下同）为0.3%时,其拉伸强度与纯PU相比提高104%,其热分解温度与MWNTs-COOH/PU相当,优于纯PU,但低于MWNT8-NH₂/PU和MWNTs-PPA/PU。     

多壁碳纳米管/聚亚苯基苯并二噁唑复合材料的微结构与性能

以甲基磺酸(MSA)为溶剂通过溶液共混法制备了不同多壁碳纳米管(MWNTs)含量的多壁碳纳米管/聚亚苯基苯并二噁唑(MWNTs/PBO)复合材料, 用扫描电镜(SEM)对热处理前后复合材料的微结构进行了分析, 并对其导电、力学和耐热性能进行了研究。结果表明: MWNTs能均匀地分散在聚合物基体中, 并能形成一定的网络结构, 热处理后的复合材料较热处理前的结构更致密, 导电性能和力学性能都有所改善, 其中MWNTs质量分数为10％的热处理后复合材料与纯PBO聚合物相比, 体积电阻率降低约9个数量级, 而拉伸强度和拉伸模量分别提高了95％和53％, 耐热性能也有一定的提高。      

Poly(vinyl alcohol) reinforced with large-diameter carbon nanotubes via spray winding

For practical application of carbon nanotube (CNT)/polymer composites, it is critical to produce the composites at high speed and large scale. In this study, multi-walled carbon nanotubes (MWNTs) with large diameter (∼45 nm) and polyvinyl alcohol (PVA) were used to increase the processing speed of a recently developed spraying winding technique. The effect of the different winding speed and sprayed solution concentration to the performance of the composite films were investigated. The CNT/PVA composites exhibit tensile strength of up to 1 GPa, and modulus of up to 70 GPa, with a CNT weight fraction of 53%. In addition, an electrical conductivity of 747 S/cm was obtained for the CNT/PVA composites. The good mechanical and electrical properties are attributed to the uniform CNTs and PVA matrix integration and the high degree of tube alignment.     

碳纳米管类型对CNTs/Lyocell复合纤维结构与性能的影响

分别采用单壁碳纳米管（SWNTs）和多壁碳纳米管（MWNTs）这两种碳纳米管（CNTs）制备不同的CNTs/Lyocell复合纤维,探讨了碳纳米管类型对复合纤维的结构与性能的影响。结果表明,碳纳米管类型并未影响CNTs/Lyocell纤维的结晶结构,质量分数为1%的SWNTs或MWNTs在Lyocell基体中分布都比较...     

Reinforcement on properties of poly(vinyl alcohol) films by embedding functionalized carbon micro coils

Carbon micro coils (CMCs) were hybridized with poly(vinyl alcohol) (PVA) through esterification reaction. The mixing of as-prepared CMC hybrid with polymer (PVA) matrix was effective to prepare PVA film where the functionalized CMC was homogeneously dispersed and embedded. The presence of CMCs in PVA film heightened the glass transition temperature of PVA. Results of tensile stress and electrical conductivity indicated that overall mechanical and electrical properties of PVA film were enforced by embedding CMC, depending on increase of the CMC concentration. These properties were further reinforced by prefunctionalization of CMC by PVA, because CMC can have an affinity to PVA in matrix through PVA immobilized on CMCs. However, mechanical and electrical properties for both nonfunctionalized and functionalized composites were depressed above a certain CMC concentration, indicating the self-orientation of CMC in the matrix, different from the behavior of carbon black.     

Mechanical strength improvement of polypropylene threads modified by PVA/CNT composite coatings

Poly (vinyl alcohol)/carbon nanotube (PVA/CNT) composite was coated on the surface of polypropylene thread for toughness enhancement. Multiwall carbon nanotubes (MWNTs) were treated in acid and alkali to get water-soluble nanotubes, and then embedded into poly (vinyl alcohol) (PVA) matrix, resulting in polymer-carbon composite with homogeneous nanotube dispersion. The stress-strain measurements show that the tensile strength and toughness of the PVA/CNT coated thread increased by 117% and 560%, respectively. These results are supportive of good interfacial bonding between the carbon nanotubes (CNTs) and polymer matrix.     

碳纳米管／聚氨酯纳米复合材料的制备及性能

采用可逆加成-断裂链转移(RAFT)聚合方法在碳纳米管表面接枝聚甲基丙烯酸甲酯和聚苯乙烯嵌段共聚物MWNT-P(MMA-b-St),对碳纳米管进行改性。采用直接共混法制备碳纳米管/水性聚氨酯纳米复合材料。通过红外光谱(FT-IR)和透射电镜(TEM)对嵌段共聚物的结构进行了表征。碳纳米管加入对乳液成膜性影响不大。热失重分析(TGA)和力学性能测试结果表明,当改性后的碳纳米管含量为聚氨酯固体份的0.75%时,复合材料的热稳定性、拉伸强度和断裂伸长率均较聚氨酯有所提高。     

Characterization and mechanical performance comparison of multiwalled carbon nanotube/polyurethane composites fabricated by electrospinning and solution casting

Multiwalled carbon nanotube/polyurethane (MWNT/PU) composites were prepared by electrospinning and solution casting. The morphological and thermal properties, and mechanical performance of the nanofiber and film composites were characterized and compared. The tensile strength of neat PU film was 9-fold higher than that of neat PU nanofibrous mat. The incorporation of MWNTs increased the tensile strength and modulus of the composite nanofibers by 69% and 140%, respectively, and 62% and 78%, respectively for composite films. The MWNT/PU composites showed an improved thermal degradation behavior, with the incorporation of low MWNT content in the composites.     

MWNTs／Lyocell复合纤维的制备及性能EI

将改性多壁碳纳米管(MWNTs)、N-甲基吗啉-N-氧化物(NMMO)水溶液及纤维素共混后制备了MWNTs/Lyocell复合纤维。采用X射线衍射仪(WAXD)、场发射扫描电镜(FSEM)、强度仪等分析了复合纤维的结构和性能。WAXD图谱显示:MWNTs已经混入到复合纤维的纤维素主体中,且未影响纤维素Ⅱ的晶型结构;FSEM及二维X射线衍射结果表明:复合纤维中,MWNTs分布均匀,且其沿纤维轴向的取向角随纺丝喷头拉伸比的增大而减小;对纤维的力学性能分析进一步表明:添加适量的MWNTs可使复合纤维的力学性能改善。其中,质量分数为1%MWNTs的复合纤维的初始模量和强度分别比未添加碳纳米管的Lyocell纤维提高了42%和22%。     

聚丙烯接枝马来酸酐修饰碳纳米管增强聚丙烯复合材料的制备及性能

采用混合溶剂的溶液法技术,对聚丙烯接枝马来酸酐(PP-g-MAH)包覆碳纳米管(MWNTs)与聚丙烯(PP)纳米复合材料的电学和力学性能进行了研究。PP-g-MAH包覆MWNTs在二甲苯溶液中呈现良好的分散性,红外结果表明,酸化碳纳米管后表面官能团如羟基、羧基与马来酸酐发生氢键作用。场发射扫描电镜(FESEM)也证明了PP-g-MAH修饰MWNTs在PP基体中分散良好,并且相容性也得到了明显改善。复合材料的拉伸强度和电导率都有较大的提高,其中导电性相比未处理碳管/聚丙烯提高了两个数量级。     

Effect of functionalized carbon nanotubes on the mechanical properties of epoxy-based composites

Abstract

In this research, composites reinforced with multi-walled carbon nanotubes (MWCNTs) in terms of their capability of absorbing energy during ballistic impact and tensile test were investigated. In order to investigate the effect of functional groups on mechanical properties of multi-wall carbon nanotubes composites, multi-walled carbon nanotubes were functionalized by COOH and NH₂. In order to investigate the penetration resistance of produced composites, the ballistic impact test with the high velocity was used. Results of the ballistic impact test imply that composites which benefit from carbon nanotubes with the carboxylic functional group have the highest value of the energy absorption. Results of the tensile test indicate, the interaction between carbon nanotubes with the carboxylic agent and the polymer matrix is much better. The ultimate stress for the sample containing nanotubes with hydroxyl functional group is 55% higher compared with the sample which does not contain any nanotubes. Reinforced composite samples which contain carbon nanotubes with the carboxylic functional group absorb 57.63% of the projectile energy and represent a better performance compared to the sample without nanotubes and the sample which consists of nanotubes with the amine functional group. The results of this study show that, uniform dispersion of nanotubes in the polymer matrix can profoundly affect mechanical properties especially the tensile strength. By functionalizing nanotubes and creating suitable functional groups, the cohesion between nanotubes and the matrix can be improved.     

Significant improvement in static and dynamic mechanical properties of graphene oxide–carbon nanotube acrylonitrile butadiene styrene hybrid composites

Herein, hybridization of graphene nanosheets and carbon nanotubes (CNTs) has been made to solve the problem of restacking of graphene nanosheets and agglomeration of CNTs. The multiwalled carbon nanotubes (MWCNTs), reduced graphene oxide (RGO) and graphene oxide–carbon nanotubes (GCNTs) reinforced acrylonitrile butadiene styrene (ABS) composites have been prepared using micro-twin-screw extruder. The effect of these reinforcements on static and dynamic mechanical properties of composites is studied. The ultimate tensile strength and elastic modulus for 7 wt.% GCNT–ABS composites show enhancement of 26.1 and 71.3% over pure ABS matrix, respectively. Various parameters such as coefficient “C” factor (the ratio of storage modulus of the composite to polymer in glassy and rubbery regions), degree of entanglement, crosslink density and adhesion factor have been calculated to analyze the interaction between fillers and polymer matrix. The 3-D hybrid structure of GCNTs overcomes the associated problem of CNTs agglomeration and graphene restacking. GCNT hybrid composites show higher dispersion as well as effectiveness for increased filler amount as compared to RGO and MWCNTs based composites. GCNTs prove its superiority over MWCNTs and RGO by showing a synergistic effect in the glass transition temperature and storage modulus. Raman spectroscopy and scanning electron microscopy are used to confirm the interaction and distribution of the filler and matrix, respectively.     

Mechanical properties of epoxy nanocomposites reinforced with very low content of amino-functionalized single-walled carbon nanotubes

Functionalized single-walled carbon nanotubes (SWNTs) with amino groups were prepared by oxidation, acylation, and amidation of SWNT surfaces. Epoxy/SWNT composite membranes were fabricated using a very low content of amino-grafted SWNTs (< or = 0.08 wt%) as fillers. SWNTs with amino groups acted as a curing agent, covalently bonding to the epoxy matrix. The influence of SWNT content on the mechanical properties of epoxy/amino-functionalized SWNT composite membrane was investigated. It is found that the tensile strength of composites is enhanced with the increase of SWNTs. Only 0.01 wt% of SWNT-R-NH, leads to improvement of the epoxy tensile strength by 9.5%, and 0.08 wt% of SWNT-R-NH2 increased tensile strength by 13.6%. For comparison purposes, epoxy/pristine-SWNT films were also prepared. The improvement of the tensile strength of the amino-functionalized SWNTs system is more remarkable than that of pristine SWNT system at very low weight-percentage loading. The amino groups on the surface of SWNTs can be covalently attached to the epoxy matrix, which effectively improves the dispersion and adhesion of SWNTs in epoxy. This leads to the enhancement in mechanical properties of the epoxy composite. Mechanical results between functionalized and pristine nanotubes are discussed in detail.     

Rheological and mechanical properties of polypropylene prepared with multi-walled carbon nanotube masterbatch

In this study, the effects of polypropylene-grafted maleic-anhydride-treated multi-walled carbon nanotubes (PP-MWNTs) on the viscoelastic behaviors and mechanical properties of a polypropylene-(PP)-based composite system were examined. The PP-MWNT/PP composites were prepared via melt mixing with a 3:1 ratio of PP-g-MA and acid-treated MWNTs at 220 degrees C. The surface characteristics of the PP-MWNTs were confirmed via Fourier transform infrared (FTIR) spectroscopy and transmission electron microscopy (TEM). The viscoelastic behavior and mechanical properties of the PP-MWNT/PP composites were confirmed using a rheometer and an ultimate testing machine (UTM). The storage and loss moduli increased with increasing PP-MWNT content. The critical intensity stress factor (K(IC)) of the PP-MWNT/PP composites at high filler loading was also higher than that of the MWNT/PP composites. In conclusion, the viscoelastic behavior and mechanical properties of MWNT/PP can be improved by grafting MWNTs to PP-g-MA.     

Mechanical and thermal properties of epoxy nanocomposites reinforced with amino-functionalized multi-walled carbon nanotubes

The functionalized multi-walled carbon nanotubes (MWNTs) with amino groups were prepared after such steps as oxidation, the addition of carboxyalkyl radicals, acylation and amidation. Besides oxidated-MWNTs/epoxy nanocomposites, amino-functionalized MWNTs/epoxy nanocomposites, in which MWNTs with amino groups acted as a curing agent and covalently attached into the epoxy matrix, were fabricated. Subsequently, the effects of MWNT content on the mechanical and thermal properties for the two systems were investigated. It is found that both the tensile strength and impact strength enhance with the increase of MWNT addition, and the most significant improvement of the tensile strength (+51%) and especially impact strength (+93%) is obtained with amine-treated MWNTs at an 1.5 wt.% content. Moreover, the thermal stability of the nanocomposites also distinctly improves. The improvement of the properties of the amine-treated MWNTs system is more remarkable than those of o-MWNTs system. The reasons for these changes were discussed.     

Effects of carbon nanotube functionalization and annealing on crystallization and mechanical properties of melt-spun carbon nanotubes/poly(ethylene terephthalate) fibers

To generate poly(ethylene terephthalate) (PET) fibers with enhanced mechanical properties, we prepared melt-spun PET fibers that incorporated pristine, acid-treated, and functionalized multi-walled carbon nanotubes (MWNTs) with 2-phenylethyl alcohol and 4-phenyl-1-butanol. The incorporation of MWNTs into the melt-spun fibers resulted in increased crystallization of PET but lower breaking stress than that of pure PET fibers, even in those containing well-dispersed functionalized MWNTs. The breaking stress of drawn composite fibers was also lower than that of pure PET fibers prepared at the same draw ratio. However, the annealing of melt-spun fibers enhanced the mechanical properties and crystallization, and the annealing effect was more dominant for composite fibers with functionalized MWNTs. These findings indicate that the presence of well-dispersed MWNTs disturbs the crystallization and orientation of PET molecules in highly stressed fibers, which differs from MWNT-induced crystallization of PET molecules in relaxed fibers.     

Mechanical properties of ABOw+MWNTs/Al hybrid composites made by squeeze cast technique

Multi-wall carbon nanotubes (MWNTs) have been considered a realistic kind of reinforcement for composite materials. In this paper, microstructure and mechanical properties of the aluminum borate whisker (ABOw) and MWNTs hybrid composites were investigated. The results show that MWNTs decrease the compressive deformation of the hybrid preforms and are kept intact in the matrix during squeeze cast processing. A small amount of MWNTs may effectively improve the modulus, strength and elongation of the hybrid composite. Decreasing micropores and strengthening the matrix, high strength MWNTs make the mechanical properties of the hybrid composite superior to the singularly reinforced ones. This makes MWNTs a promising material for novel micro/nanohybrid composite.     

不同官能化碳纳米管对MWCNTs-碳纤维/环氧树脂复合材料力学性能的影响

为研究加入不同官能化碳纳米管对环氧树脂力学性能的影响,通过对羧基化多壁碳纳米管(MWCNTsCOOH)进行化学处理,得到表面接枝乙二胺的碳纳米管(MWCNTs-EDA)。分别将MWCNTs-COOH和MWCNTs-EDA分散在环氧树脂中,通过热熔法制备环氧树脂中含有碳纳米管的T700碳纤维预浸料,并热压成准各向同性复合材料层合板。结果表明:MWCNTs-EDA在环氧树脂中的分散性优于MWCNTs-COOH,MWCNTsEDA本身具有固化反应活性,加入后对基体的交联密度影响较小。与MWCNTs-COOH相比,MWCNTs-EDA可以有效改善环氧树脂及碳纤维/环氧树脂复合材料的力学性能。当MWCNTs-EDA含量为1.0wt%时,MWCNTs-碳纤维/环氧树脂准各向同性复合材料层合板的压缩性能、弯曲性能和冲击后压缩强度分别提高了14.7%、40.9%和20.6%。     

Multiwalled carbon nanotubes functionalized with 7-octenyltrichlorosilane and n-octyltrichlorosilane: dispersion in Sylgard?184 silicone and Young’s modulus

Sylgard^?184/multiwalled carbon nanotube (MWNT) composites have been prepared by in situ polymerization using purified and functionalized multiwalled carbon nanotubes (f-MWNTs) as fillers. Surface modification of the MWNTs has been carried out by silanization with 7-octenyltrichlorosilane (7OTCS) and n-octyltrichlorosilane (nOTCS). The modification and dispersion of the carbon nanotubes in composites were characterized by X-ray photoelectron spectroscopy (XPS), transmission electron spectroscopy (TEM), and high-resolution transmission electron spectroscopy (HRTEM). Young’s modulus results were derived from indentation testing. It is shown that the terminal-vinyl group of 7OTCS molecules plays an essential role for both the dispersion of the f-MWNTs in the composite and its mechanical properties. At loading as low as 0.2 wt%, the Young’s modulus is shown to increase up to 50%. This is interpreted as resulting from a combination of the good compatibility in the forming silicone matrix of the MWNTs coated with a siloxane network, on the one hand, and the covalent links created between the terminal-vinyl groups and the host matrix in formation, on the other hand.