Investigation on the multiwalled carbon nanotubes reinforced polyamide 6/polypropylene composites

Multiwalled carbon nanotubes (MWNTs) reinforced polyamide 6/polypropylene (PA6/PP = 70/30) composites were prepared by melt compounding. Maleated polypropylene (MPP) was used as a compatibilizer for the composites. The morphology, mechanical properties, thermal stability, rheological properties and crystallization behavior of the composites were investigated. It was found that the addition of MWNTs to PA6/PP blend resulted in decrease in the size of the dispersed particles. Most of MWNTs were selectively dispersed in the PA6 phase and a small amount of MWNTs were located in the interphase between PA6 matrix and PP phase as characterized by scanning electric microscopy. The strength and stiffness of the PA6/PP blend were greatly improved by the addition of MWNTs. The MPP and MWNTs had a synergistic effect on the improvement ofthe thermal stability. In addition, the complex viscosity, storage modulus and loss modulus of the composites increased with the addition of MWNTs or MPP. MWNTs could induce the formation of α crystalline form of PA6. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Electrical properties and morphology of highly conductive composites based on polypropylene and hybrid fillers

Electrically conductive polypropylene/hybrid filler (PP/GO–MWNTs) and PP/MWNTs composite have been prepared via melt blending PP with the hybrid filler (multiwalled carbon nanotubes (MWNTs) and graphite oxide (GO)) and the single filler (MWNTs), respectively. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to research the interior morphology of the GO–MWNTs hybrid filler, and the dispersion of the hybrid filler in the PP matrix is also observed by SEM. The results show that a clear reduction in electrical resistivity and percolation threshold of PP/GO–MWNTs composite can be ascribed to the corporation of GO. The electrical properties of PP composites were improved owing to the effective conductive networks formed by hybrid filler.     

Dispersion and mechanical properties of polypropylene/multiwall carbon nanotubes composites obtained via dynamic packing injection molding

In this article, polypropylene (PP)/multiwall carbon nanotubes (MWNTs) composites were prepared through dynamic packing injection molding, in which the oscillatory shear was exerted on the molten composite during packing and solidification stage of injection‐molding. A simultaneous increase of tensile strength and impact strength has been achieved for PP/MWNTs composites containing only 0.6 wt % MWNTs. Particularly, the impact strength was found increased by almost 50% at such low MWNTs content. These improvements in properties were attributed to uniform dispersion and possible orientation of nanotube induced by shear stress. It was suggested that the dynamic packing injection molding could provide much strong shear force for better dispersion of MWNTs in PP matrix, on one hand, but breakdown the aspect ratio of MWNTs, on the other. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1880–1886, 2007     

PP/MWNTs和PP/OMMT复合材料的热降解动力学研究

采用熔融共混法制备了聚丙烯/多壁碳纳米管(PP/MWNTs)与聚丙烯/纳米有机蒙脱土(PP/OMMT)复合材料,利用热重分析法研究了PP、PP/MWNTs及PP/OMMT在氮气气氛中的热降解过程,并采用Kissinger及Ozawa方法研究了复合材料的热降解动力学及热降解表观活化能.结果表明,MWNTs和OMMT的加入...     

Crystallization behavior of biodegradable poly(L‐lactide)/multiwalled carbon nanotubes nanocomposites from the amorphous state

Crystallization behavior of biodegradable poly(L ‐lactide) (PLLA) and its nanocomposites at different carboxyl‐functionalized multiwalled carbon nanotubes (f‐MWNTs) contents from the amorphous state was studied in detail in this work. For the isothermal cold crystallization, the presence of f‐MWNTs enhances the isothermal cold crystallization of PLLA in the nanocomposites compared with that of neat PLLA at the same crystallization temperature; moreover, the overall cold crystallization rate of PLLA increases with increasing the f‐MWNTs content in the PLLA matrix while the crystallization mechanism does not change. For the nonisothermal crystallization, the f‐MWNTs also accelerate the crystallization process of PLLA. In addition, the activation energies of nonisothermal cold crystallization process were calculated using both the Kissinger and Friedman methods. The cold crystallization activation energies of PLLA are higher in the nanocomposites than in neat PLLA, indicating that the addition of f‐MWNTs into the PLLA matrix acts as a physical hindrance to retard crystallization. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Excellent tensile ductility in highly oriented injection-molded bars of polypropylene/carbon nanotubes composites

Multi-wall carbon nanotubes (MWNTs) grafted with alkyl chain were used for reinforcement of polypropylene (PP). For achieving excellent tensile properties, the as-prepared PP/MWNTs composites were subjected to a unique injection molding, as so-called dynamic packing injection molding, to induce a highly oriented structure with both PP chains and MWNTs aligned along the shear flow direction. Not only Young's modulus and tensile strength were enhanced, as expected for oriented materials, but also more importantly composites containing only 0.1-0.3 wt% MWNTs were much ductile compared with the polymer matrix. The addition of PP-g-MMA made a drop in the elongation at break to only 15%; however, it could be improved to 80-100% after incorporation of small amount of MWNTs. This improvement in ductility could be ascribed to: (1) the increased mobility of both the PP chains and MWNTs, as they are oriented along tensile deformation direction and (2) the bridging effect of the oriented MWNTs on the crack development during tensile failure.     

Thermal and flame retardant properties of ethylene‐vinyl acetate copolymer/modified multiwalled carbon nanotube composites

The synthesized flame retardant 9,10‐dihydro‐9‐oxa‐10‐phosphaphanthrene‐10‐oxide/vinyl methyl dimethoxysilane (DV) was used to modify multiwalled carbon nanotubes (MWNTs). The results of FTIR, ¹H‐NMR, and TGA measurements show that DV has been covalently grafted onto the surfaces of MWNTs, and the MWNTs‐g‐DV is obtained successfully. Transmission electron microscopy images show that a core‐shell nanostructure appears with MWNTs as the core and the DV thin layers as the shell, and the modified MWNTs with DV can achieve better dispersion than unmodified MWNTs in EVM matrix. Thermogravimetric analysis and cone calorimeter tests indicate that the thermal stability and flame retardant are improved for the presence of the MWNTs in EVM matrix. Moreover, the improvement is more evident for EVM/MWNTs‐g‐DV composite compared to unmodified MWNTs‐based composite, which can be attributed to the better dispersion of the DV‐modified MWNTs and to the chemical structure of the combustion residue. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Fabrication and characterization of homogeneous composites of polypropylene and multiwalled carbon nanotubes

The polypropylene‐grafted multiwalled carbon nanotubes (PP‐MWCNTs) were produced from the reaction of PP containing the hydroxyl groups and MWCNTs having 2‐bromoisobutyryl groups. The PP‐MWCNTs had a significantly rougher surface than the original MWCNTs. PP‐MWCNTs had PP layers of thickness 10–15 nm on the outer walls of the MWCNTs. PP/PP‐MWCNT composites and PP/MWCNT composites were prepared by solution mixing in o‐xylene. Unlike PP/MWCNT composites, PP‐MWCNTs were homogeneously dispersed in the PP matrix. As a consequence, the thermal stability and conductivity of PP/PP‐MWCNT composites were dramatically improved even if only 1 wt % of PP‐MWNTs was added to the PP matrix. The good miscibility of PP and PP‐MWCNTs plays a critical role in the formation of the homogeneous composites and leads the high thermal stability and conductivity. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Properties and structure of MWNTs/cellulose composite fibers prepared by Lyocell process

Lyocell fiber is a new kind of regenerated cellulose fiber and expected to replace the Rayon fiber to be not only used in the textile field but also used in the fields of industry and aerospace after being modified. In this work, the multi‐walled carbon nanotubes (MWNTs)/Lyocell composite fibers were prepared under different draw ratios by dry‐wet spinning and their electrical properties, mechanical properties, and structure were investigated. It was found that an appropriate amount of MWNTs could be dispersed homogeneously in the Lyocell matrix and could improve the mechanical and thermal properties of composite fiber. The results of wide angle X‐ray diffraction (WAXD) showed that the MWNTs in the composite fiber almost aligned along the axis of the fibers and the orientation of MWNTs increased with the increasing draw ratio. Furthermore, it was found that more MWNTs content and lower draw ratio could improve the electrical conductance of the composite fiber. The composite fiber containing 5 wt % MWNTs has a volume conductivity of 8.8 × 10^?4 S/cm, which is five orders higher than that of pure Lyocell fiber. These results indicate that the MWNTs/Lyocell composite fiber has potential applications in the areas of precursor of carbon fiber and conductive fiber. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

PP/KPEG/MWNTs导热复合材料制备及性能

将可膨胀石墨(KPEG)和多壁碳纳米管(MWNTs)混合填料填充至聚丙烯(PP)制备PP/KPEG/MWNTs导热复合材料。保持混合填料总质量分数30%不变,改变两者质量比进行试验。结果表明,随着MWNTs填充比例增加,导热复合材料的拉伸强度呈先增大后减小趋势,而缺口冲击强度总体呈下降趋势。与纯PP相比,当MWNTs与KPEG质量比为1∶5(MWNTs质量分数为5%)时,导热复合材料的热导率提高了328.4%;MWNTs可提高复合材料热稳定性,但改变其与KPEG质量比在试验范围内对热稳定性影响较弱。     

Preparation and characterization of alkylated carbon nanotube/polyimide nanocomposites

BACKGROUND: The development of carbon nanotube‐reinforced composites has been impeded by the difficult dispersion of the nanotubes in polymers and the weak interaction between the nanofiller and matrices. Efficient dispersion of carbon nanotubes is essential for the formation of a functional nanotube network in a composite matrix. RESULTS: Multiwalled carbon nanotubes (MWNTs) were incorporated into a polyimide matrix to produce MWNT/polyimide nanocomposites. To disperse well the MWNTs in the matrix and thus improve the interfacial adhesion between the nanotubes and the polymer, ‘branches’ were grafted onto the surface of the nanotubes by reacting octadecyl isocyanate with carboxylated MWNTs. The functionalized MWNTs were suspended in a precursor solution, and the dispersion was cast, followed by drying and imidization to obtain MWNT/polyimide nanocomposites. CONCLUSION: The functionalized MWNTs appear as a homogeneous dispersion in the polymer matrix. The thermal stability and the mechanical properties are greatly improved, which is attributed to the strong interactions between the functionalized MWNTs and the polyimide matrix. Copyright © 2009 Society of Chemical Industry     

Mechanical,thermal, and rheological behavior of ethylene methyl acrylate‐MWNT nanocomposites

Mechanical, thermal, and rheological properties of ethylene methyl acrylate (EMA) composites reinforced with multiwalled carbon nanotubes (MWNTs) have been reported here. Morphological analyses revealed that MWNTs are more uniformly dispersed in EMA upto 3.5 wt% MWNTs loading. Uniform dispersion of MWNTs in EMA matrix leads to decreased crystallinity and increased crystallite size. These are reflected in the mechanical and thermal properties of the composites. The storage moduli of the composites significantly increase by the incorporation of MWNTs, particularly at higher temperatures. The nanocomposites register a slightly higher viscosity than that of neat EMA depending on the contents of MWNTs. Storage modulus (in dynamic shear) increases especially at higher frequency levels due to increased polymer–filler interactions. Dynamic and steady shear rheological properties register a good correlation in regard to the viscous versus elastic response of the nanocomposites. The morphology correlates well with the dynamic rheological characteristics of these nanocomposites. POLYM. ENG. SCI., 2012. © 2011 Society of Plastics Engineers     

Extension‐induced mechanical reinforcement in melt‐spun fibers of polyamide 66/multiwalled carbon nanotube composites

In this work, polyamide 66 (PA66) and its composites with multiwalled carbon nanotubes (MWNTs) were melt spun into fibers at different draw ratios. PA66 fibers at high draw ratio demonstrate a 40% increase in tensile strength, 66% increase in modulus and a considerable increase in toughness. It is demonstrated that this reinforcement can be mainly attributed to high‐draw‐ratio‐induced good dispersion and orientation of MWNTs, particularly the enhanced interfacial adhesion between MWNT and matrix thanks to interfacial crystallization. Our work provides a simple but efficient method to achieve good dispersion and strong interfacial interaction through melt spinning. Copyright © 2011 Society of Chemical Industry     

Effective reinforcement of carbon nanotubes in polypropylene matrices

This study describes an attempt to mechanically reinforce polypropylene (PP) using multi‐wall carbon nanotubes (MWNTs) through a melt compounding process followed by hot‐pressing and solid state drawing. The effect of a high density polyethylene (HDPE) coating on MWNTs and melt flow index (MFI) of PP on the dispersion of MWNTs and composite properties are studied by means of mechanical tests, transmission electron microscopy (TEM), scanning electron microscope (SEM), differential scanning calorimetry (DSC), and wide angle x‐ray diffraction (WAXD). Highly orientated composite tapes are prepared to fully utilize the properties of MWNTs in uniaxial direction. Highly aligned MWNTs are shown by SEM, while highly oriented polymer chains are characterized by WAXD. Composite theory is used to analysis the results and indicate that effective reinforcement of PP by MWNTs is highest at relatively low filler content and draw ratios. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Enhanced interactions between multi-walled carbon nanotubes and polystyrene induced by melt mixing

The effect of melt mixing on the interaction between multi-walled carbon nanotubes (MWNTs) and polystyrene (PS) matrix has been investigated. The interaction between pristine MWNTs and PS in solution was found to exist but not strong enough to allow MWNTs to be soluble in solvent. In contrast, this interaction between MWNTs and PS was significantly enhanced by melt mixing, which led to increased amount of PS-functionalized MWNT exhibiting good solubility in some solvents. The mechanism of melt mixing on this enhanced interaction was attributed to both chemical bonding and physical interaction during the melt mixing.     

Preparation and properties of novel epoxy composites containing electrospun PA6/F‐MWNTs fibers

The Nylon 6 (PA6)/the functionalized multiwalled carbon nanotubes (F‐MWNTs) fibrous membranes were fabricated by electrospinning, and then incorporated into an epoxy matrix. Their morphology, thermal stability, mechanical properties, thermal conductivities, and electrical resistivity were investigated. The electrospun PA6/F‐MWNTs fibers performed as a skeleton in the epoxy matrix, and the well interfacial adhesion between the epoxy matrix and the PA6/F‐MWNTs fibers leads to high mechanical properties of composites. The PA6 serves as an intermediate layer and alleviates the modulus mismatch between the stiff MWNTs and the soft epoxy matrix. The thermal conductivities of the epoxy composites increase by 27.3, 35.0, and 36.1%, respectively, with 0.5, 1 and 1.5 wt% F‐MWNTs loading in the PA6/F‐MWNTs fibers. At the same time, the PA6 simultaneously retains the high electrical resistivity of these epoxy composites. POLYM. ENG. SCI., 56:1259–1266, 2016. © 2016 Society of Plastics Engineers     

Fabrication and characterization of solution cast MWNTs/PEI nanocomposites

Under mild conditions with the aid of ultrasonic, multi‐walled carbon nanotubes (MWNTs) have been functionalized by mixed acid treatment which was proved by FTIR and XPS. According to SEM, acid treatment on MWNTs decreased the thickness of the membrane. However, no devastating damage and fracture happened on MWNTs after acid treatment under mild conditions. Precipitation observation illustrated that the enhanced solubility of MWNTs in water, ethanol, and dimethylformaide (DMF). Further, MWNTs/polyetherimide (PEI) nanocomposite films have been prepared by the simple solution casting method. The dispersion of MWNTs in polyetherimide (PEI) matrix was observed by Atomic Force Microscopy (AFM) which illustrated the improved dispersion for acid treated MWNTs in PEI. The adding of MWNTs in PEI decreased the dispersive component of surface energy and increased the polar component of surface energy, which resulted in the decrement of film surface energy. Differential scanning calorimetry showed that the glass transition temperature of PEI increased by about 4°C after the introduction of MWNTs. This improvement was related to the better affinity between MWNTs and PEI matrix, which also resulted in the improvement of mechanical strength in MWNTs/PEI nanocomposites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Functionalization of multiwalled carbon nanotubes with amphiphilic poly(aspartic acid)

A new method to functionalize multiwalled carbon nanotubes (MWNTs) with amphiphilic poly(aspartic acid) was investigated. The amphiphilic polymer (PASP‐C16) was synthesized by thermal condensation and aminolysis by hexadecylamine, followed by hydrolysis of the remaining succinimide units in the polymer backbone. The functionalization of MWNTs was achieved by physical adsorption of the biopolymer onto the surfaces of MWNTs. Ultraviolet‐visible ( UV‐vis) spectra showed that the functionalized MWNTs had a good aqueous dispersity and solubility. The interaction of PASP‐C16 with MWNTs was investigated by analyzing X‐ray diffraction (XRD) patterns, circular dichroism (CD), spectra and high‐resolution transmission electron microscopy ( HRTEM ). From the XRD patterns, it can be known that the aggregate of PASP‐C16 due to intermolecular interaction between hexadecyl chains has been reduced when the polymer interacting with MWNTs. CD spectra indicated that the interaction of hexadecyl chains of PASP‐C16 with the wall of MWNTs is the major interaction between PASP‐C16 and MWNTs, and MWNTs were covered by the poly(aspatic acid) backbone. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Protein adsorption on functionalized multiwalled carbon nanotubes with amino‐cyclodextrin

A novel amino‐cyclodextrin was synthesized, and it was covalently attached to multiwalled carbon nanotubes (MWNTs). The functionalized MWNTs (f‐MWNTs) have very good aqueous dispersibility. Bovine serum albumin (BSA) was adsorbed onto f‐MWNTs through noncovalent interactions, including the hydrophobic interaction of the residues of BSA with the wall of MWNT and the guest–host interaction of the residues with the cyclodextrin (CD) moieties of f‐MWNTs. The ultraviolet–visible (UV–vis) absorption of the f‐MWNT‐BSA hybrid was measured with UV–vis spectrometer, and the absorbance can be described well with the Beer–Lambert law. The X‐ray diffraction patterns have indicated that the crystalline form of BSA has been changed after the adsorption of BSA on f‐MWNTs. The circular dichroism spectra have shown that a high percentage of α‐helical content can be retained for BSA adsorbed on f‐MWNTs. The results also indicate that the change of secondary structure of BSA is mainly due to the hydrophobic interaction of the residues of BSA with the wall of f‐MWNT, whereas the secondary structure is much less affected by the interaction of the CD moieties with BSA. © 2011 American Institute of Chemical Engineers AIChE J, 2011     

Effects of toughening agents on the behaviors of bamboo plastic composites

Three kinds of reactive toughening agents of bamboo plastic composites are studied in this article. The bio‐fiber keeps high polarity for the hydroxyl groups of the surface, while polypropylene (PP) matrix resin phase is nonpolar. So, the interfacial compatibility between matrix and enhanced phase is poor. The anhydride in maleic anhydride grafted polypropylene can react with the hydroxyls. A large number of hydroxyl groups on the fiber surface are reduced, and the interfacial bond strength is improved. Three reactive toughening agents: glycidyl methacrylate grafted poly(ethylene‐1‐octene), maleic anhydride grafted poly(ethylene‐octene), and poly(ethylene‐butylacrylate‐glycidyl methacrylate) are chosen to improve the impact toughness. The mechanical properties, compatibility, phase structure, water absorption, and thermal properties of PP blends are all investigated. When the content of toughening agents are controlled between 6% and 8%, not only the impact strength is greatly improved but also the other properties of PP are less affected, which makes the composites with comprehensive and practical applications. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers