Pseudoreinforcement effect of multiwalled carbon nanotubes in epoxy matrix composites

The carbon nanotube possesses outstanding physical properties. Theoretically, adding carbon nanotubes into a polymer matrix can remarkably improve the mechanical properties of the polymer matrix. In the present work, a series of composites was prepared by incorporating multiwalled carbon nanotubes (MWNTs) into an epoxy resin. The influences of MWNT content and curing temperature on the flexural properties of the epoxy resin were investigated. The results showed that a very low MWNT content should be used to ensure homogeneous dispersion of MWNTs in the epoxy matrix. A higher MWNT content may lead to deteriorated mechanical properties of the composites because of the aggregation of MWNTs. A decline in the flexural properties of the neat epoxy resin with increasing curing temperature was found. However, under the same curing conditions, improvement in flexural properties was observed for the composite with the low MWNT content and a mild curing temperature. The improvement was far beyond the predictions of the traditional short‐fiber composite theory. In fact, this improvement should be attributed to the retarding effect of MWNTs on the curing reaction of epoxy matrix. Therefore, the improvement in the flexural properties was only a pseudoreinforcement effect, not a nano‐reinforcement effect of the MWNTs on the epoxy resin. Perhaps, it is better for MWNTs to be used as functional fillers, such as electrical or thermal conductive fillers, than as reinforcements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 3664–3672, 2006     

Effect of surface modification of aluminum nitride on electrical and thermal characterizations of thermosetting polymeric nanocomposites

Thermally conductive composites and nanocomposites composed of epoxy resin as base matrix and aluminum nitride (AlN) as micro and nanofiller have been studied at variable temperatures and loading of AlN. To improve the dispersion of the filler within the polymer matrix, AlN was surface modified with silane‐coupling agent. Thermogravimetric analysis confirmed the interfacial bonding of epoxy‐ and silane‐modified AlN. The dielectric properties of epoxy/AlN composites and nanocomposites have been studied at variable percentage of filler. Test result indicated an increase of thermal conductivity of the composites at 20 wt% of AlN. Also, silane‐treated composites exhibited improved electrical conductivity properties, whereas the electrical insulation property decreased in terms of dielectric strength and resistivity. POLYM. COMPOS., 2013. © 2012 Society of Plastics Engineers     

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     

Effects of novolac resin modification on mechanical properties of carbon fiber/epoxy composites

The epoxy resin matrix of carbon fiber (CF)‐reinforced epoxy composites was modified with novolac resin (NR) to improve the matrix‐dominated mechanical properties of composites. Flexural strength, interlaminar shear strength (ILSS), and impact strength were measured with unfilled, 7 wt% NR, 13 wt% NR, and 18 wt% NR filled to epoxy to identify the effect of adding NR on the mechanical properties of composites. The results showed that both interfacial and impact properties of composites were improved except for flexural property. The largest improvement in ILSS and impact strength were obtained with 13 wt% loading of NR. ILSS and impact strength were improved by 7.3% and 38.6%, respectively, compared with the composite without NR. The fracture and surface morphologies of the composite specimens were characterized by scanning electron microscopy. Intimate bonding of the fibers and the matrix was evident with the content of 7–13 wt% NR range. Decrease of crosslinking density and formation of NR transition layer were deduced with adding NR. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Thermal diffusivity of nanocarbon composites

This study was performed to measure the thermal diffusivity of different types of nanocarbon composites. Thermoexfoliated graphite (TEG), ultrasonically dispersed TEG, and multiwalled carbon nanotubes were used as fillers in epoxy polymer matrixes. The nanocarbon filler content was 1–10 wt%. The temperature dependence of the thermal conductivity and the heat capacity were extensively characterized in the temperature range between 150 and 425 K. For this purpose, the thermal diffusivity of the composites was investigated by two experimental methods: dynamic λ‐calorimeter and photoacoustic. The comparative analysis of thermal diffusivity of compacted TEG samples with different densities and of nanocarbon‐epoxy with different filler content was carried out. It was found that for the composites with a low distribution of the nanocarbon filler, the thermal diffusivity increases and that the value is determined by the structural and morphological properties of the filler. The orientation function for the TEG‐epoxy composites and the compact TEG samples differs due to the epoxy matrix that reduced anisotropy of the composite. POLYM. COMPOS., 2011. © 2010 Society of Plastics Engineers     

Electrical conductivity and thermal properties of acrylonitrile‐butadiene‐styrene filled with multiwall carbon nanotubes

Composites of Acrylonitrile‐butadiene‐styrene (ABS) and multiwall carbon nanotubes (MWNTs) have been prepared via solution‐blending. The electrical conductivity of these composites is analyzed. The MWNT‐filled ABS shows percolation point of the electrical conductivity at low filler loadings (1–2 wt%). The micro‐structure of the composites is also analyzed by scanning electron microscopy showing that the nanotubes are dispersed quite homogeneously in the polymer‐matrix. The thermogravimetric analysis is used to study the thermal degradation of ABS/MWNTs composites in nitrogen. MWNTs tend to destabilize the ABS matrix in the 220–450°C degradation regions but improve the thermal stability in the 425–850°C regions. With further addition of MWNTs, the features of the destabilization in the 220–450°C degradation region did not change much but in the 425–850°C degradation process, the MWNTs reinforced stabilization and the quality of the char residue of amorphous carbon deposition was improved. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Strengthening and toughening of thermoplastic polyolefin elastomer using polypropylene‐grafted multiwalled carbon nanotubes

In this article, it is demonstrated that simultaneously strengthened and toughened nanocomposites based on polypropylene/EPDM thermoplastic elastomer (TPO) matrix can be achieved through enhanced adhesion between MWNTs and polymer matrix by using PP grafted multiwalled carbon nanotubes (MWNTs). To improve the interface between filler and matrix, MWNTs were treated with acid, or covalently linked to polypropylene. The chemical and morphological transformation of the modified MWNTs, and its effect on the morphology and mechanical properties of the composites are investigated. The strengthening and toughening mechanism is discussed regarding the structural property relationship. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Investigation of multi‐walled carbon nanotube‐reinforced high‐density polyethylene/carbon black nanocomposites using electrical,DSC and positron lifetime spectroscopy techniques

BACKGROUND: The positive temperature coefficient (PTC) effect on material properties has attracted much attention in recent years due to the prospects of many applications like temperature sensors, thermistors, self‐regulating heaters, etc. It has been suggested that incorporation of multi‐walled carbon nanotubes (MWNTs) into carbon black (CB)‐filled polymers could improve the electrical properties of composites due to high conductivity and network structure and significantly reduce the required CB loading. RESULTS: We observed no change in melting temperature and crystalline transition temperature on addition of MWNTs. However, the heat of fusion decreases as the amount of conducting carboxylated MWNT (c‐MWNT) filler increases and the resistivity of the composite decreases. The free volume shows an increase up to 1.5 wt% of c‐MWNT content and then decreases. CONCLUSION: Well‐developed crystals could not be formed due to restricted chain mobility as filler content increases. This results in minimum intermolecular interactions, and thus a decreased heat of fusion. A composite with c‐MWNT content of 0.5 wt% showed the highest PTC and higher resistivity at 150 °C possibly due to the formation of flocculated structures at elevated temperature. For filler content greater than 1.5 wt%, the decrease in free volume may be due to restricted chain mobility. 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     

Mechanical properties of graphene nanoplatelet/epoxy composites

Because of their high‐specific stiffness, carbon‐filled epoxy composites can be used in structural components in fixed‐wing aircraft. Graphene nanoplatelets (GNPs) are short stacks of individual layers of graphite that are a newly developed, lower cost material that often increases the composite tensile modulus. In this work, researchers fabricated neat epoxy (EPON 862 with Curing Agent W) and 1–6 wt % GNP in epoxy composites. The cure cycle used for this aerospace epoxy resin was 2 h at 121°C followed by 2 h at 177°C. These materials were tested for tensile properties using typical macroscopic measurements. Nanoindentation was also used to determine modulus and creep compliance. These macroscopic results showed that the tensile modulus increased from 2.72 GPa for the neat epoxy to 3.36 GPa for 6 wt % (3.7 vol %) GNP in epoxy composite. The modulus results from nanoindentation followed this same trend. For loadings from 10 to 45 mN, the creep compliance for the neat epoxy and GNP/epoxy composites was similar. The GNP aspect ratio in the composite samples was confirmed to be similar to that of the as‐received material by using the percolation threshold measured from electrical resistivity measurements. Using this GNP aspect ratio, the two‐dimensional randomly oriented filler Halpin–Tsai model adjusted for platelet filler shape predicts the tensile modulus well for the GNP/epoxy composites. Per the authors' knowledge, mechanical properties and modeling for this GNP/epoxy system have never been reported in the open literature. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Tribological and electrical properties of silica‐filled epoxy nanocomposites

The tribological and electrical properties of epoxy composites filled with nano‐sized silica particles are studied and discussed in this article. To enhance the interfacial interaction between the fillers and the matrix, nanoparticles were pretreated with silane coupling agent. Dry sliding wear tests were carried out with configuration of composite sample on a rotating steel disc. Electrical measurements such as AC breakdown voltage, at 50 Hz, high voltage‐low current arc resistance and wet tracking resistance were carried out. The results reveal the influence of nanosized silica loading on wear resistance of the epoxy. It is observed that 10 wt% loading of silica is very effective in reducing the wear loss. With further increase of silica filler loading, the nanoparticles agglomerated and resulted in increase of the specific wear rate. The influence of silica particles on the specific wear rate is more pronounced under sliding wear situation. The influence of silica particle loading on epoxy is evident in the results of electrical parameters like dielectric strength, arc resistance and tracking resistance. These parameters showed improvement with filler loading up to 15 wt% and beyond this value of filler loading noticeable deterioration was observed. The effects of electrical stresses in the morphologies of the surfaces of epoxy nanocomposites are discussed. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Tribological behavior of epoxy composites containing reactive SiC nanoparticles

The present article evaluated the sliding wear behaviors of epoxy and its composites filled with SiC nanoparticles. Polyglycidyl methacrylate (PGMA) and a copolymer of glycidyl methacrylate and styrene were grafted onto the nanoparticles as a measure of surface pretreatment, respectively. The grafted polymers were selected because the epoxide groups on PGMA would take part in the curing reaction of epoxy resin and covalently connect the nanoparticles with the matrix, while styrene acted as a copolymerized monomer to adjust the amount of the reactive groups of the grafted macromolecular chains, and hence the compatibility between the grafted polymers and the matrix. In comparison to the composites filled with untreated nano‐SiC particles, the composites with the grafted nano‐SiC exhibit improved sliding wear resistance and reduced frictional coefficient owing to the chemical bonding at the filler/matrix interface. The results were analyzed in terms of structure‐properties relationship of the composites. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 2608–2619, 2007     

A comparative analysis of woven jute/glass hybrid polymer composite with and without reinforcing of fly ash particles

The objective of this research article is to compare the mechanical and tribological properties of jute‐glass‐fiber‐reinforced epoxy (J‐G‐E) hybrid composites with and without fly ash particulate filler. A dry hand lay‐up technique is used to fabricate all the laminates. The properties including flexural strength, tensile strength, flexural modulus, and erosion behavior of all the composites are evaluated as per American Society for Testing and Materials (ASTM) standards. The fly ash particulate‐filled hybrid composite shows a better mechanical and tribological property. The maximum flexural strength and flexural modulus are obtained for GJGJ+ 5 wt% fly ash filler epoxy composites. Whereas the maximum tensile strength is obtained for GJJG+ 10 wt% fly ash filler epoxy composites. Scanning Electron Microscopy (SEM) analysis also has been carried out to categorize mechanical and tribological behavior of composites. POLYM. COMPOS. 37:658–665, 2016. © 2014 Society of Plastics Engineers     

多壁碳纳米管／环氧树脂复合材料性能研究

采用物理机械方法与化学方法相结合的手段,制备了多壁碳纳米管（MWNTS）／环氧树脂（Epoxy）复合材料。通过力学拉伸试验测试了MWNTs/Epoxy复合材料拉伸强度和拉伸模量与MWNTS添加量的关系,利用扫描电镜（SEM）分析了MWNTS／Epoxy复合材料的拉伸断面,并用表面电阻测试仪对所制备的碳纳米管复合材料进行了电学性能测试。结果表明：经过化学酸化的方法处理后的MWNTS在复合材料中的分散得到了改善,力学性能也得到了明显的提高,但酸处理后的复合材料的电学性能明显低于未处理的复合材料。     

Poly(propylene) composite with hybrid nanofiller: Dynamic properties

Mechanical, impact, and relaxation properties of in situ synthesized carbon nanotubes‐polyaniline (CNT‐PANi) hybrid nanoparticle‐filled poly(propylene) (PP) composites with or without an amphiphilic dispersing agent were investigated using tensile testing, notched Charpy impact testing, and dynamical mechanical testing methods. The reference material was MWCNT filled PP composite. Ethyl gallate (EG) was the dispersing agent which realizes high conductivity in PP composites with hybrid filler. Measured properties showed quite similar behavior of CNT‐PANi hybrid and neat CNT filled composites. Addition of 20% EG in PP did not cause essential differences compared to the neat PP. When the dispersing agent was added in filler containing PP composites, remarkable effects were observed, especially in PP‐hybrid composites. Mechanically, these materials had improved tensile properties, but they were brittle compared to the materials without dispersing agent. Dynamic mechanical analysis showed improvement in storage modulus, and in loss modulus the α transition was well observable. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Functionalizing carbon nanotubes by grafting cyclotriphosphazene derivative to improve both mechanical strength and flame retardancy

An intumescent flame‐retardant, hex(4‐carboxylphenoxy) cyclotriphosphazene (HCPCP) was synthesized and covalently grafted on to the surface of multiwalled carbon nanotubes (MWNTs) to obtain MWNT‐HCPCP. MWNT/epoxy resin (EP) and MWNT‐HCPCP/ EP nanocomposites were prepared via thermal curing. Transmission electron microscopy results showed that a core–shell structure with MWNTs as the hard core and HCPCP as the soft shell were formed after HCPCP (10 wt%) were attached to the MWNTs. The results of flammability tests showed an increased limited oxygen index value for MWNT‐HCPCP/EP nanocomposites. The mechanical properties including tensile strength and elongation were both dramatically improved due to the better dispersion of MWNT‐HCPCP in the EP matrix. The grafting of HCPCP can improve both the dispersion of nanotubes in polymer matrix and flame retardancy of the nanocomposites. POLYM. COMPOS., 35:2187–2193, 2014. © 2014 Society of Plastics Engineers     

Reinforcement effect of nanodiamond on properties of epoxy matrix

Epoxy/nanocrystalline diamond nanocomposites composites were prepared by dispersing ultrasonically, 0.4, 0.7, 1.0, and 4.0 wt% acid‐treated nanocrystalline diamond (NCD) powder in epoxy matrix. Fourier infrared spectroscopy was utilized to study the moieties attached to the nanodiamond particles. The trace elements present in NCD powder before and after acid treatment were analyzed by ion beam techniques. Thermomechanical properties of the nanocomposites showed that incorporation of low content (0.4 wt%) of nanodiamond powder into epoxy matrix enhanced the storage modulus, loss modulus, and hardness by ∼68, ∼55, and ∼86%, respectively, over neat epoxy. By increasing the concentration of modified NCD to 0.7 wt% resulted in lower values of hardness and thermomechanical properties but still remain higher than neat epoxy. An increasing trend in properties was again observed at 4 wt% concentration of modified nanofiller. The glass transition temperature was up shifted to ∼110°C over neat epoxy. The mechanisms responsible for enhanced properties of epoxy matrix are also discussed in detail. POLYM. COMPOS., 34:811–818, 2013. © 2013 Society of Plastics Engineers     

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     

Fabrication and dielectric properties of poly(ether ether ketone)/polyimide blends with selectively distributed multi‐walled carbon nanotubes

The distribution and contents of conductive fillers have a decisive influence on the dielectric properties of polymer/conductive filler composites. Herein, we clarified how the phase morphology and filler contents affect the dielectric properties of poly(ether ether ketone) (PEEK)/polyimide (TPI)/multi‐walled carbon nanotubes (MWCNTs) composites, in which MWCNTs were selectively located in the TPI phase. Firstly, PEEK/TPI/MWCNTs composites with identical MWCNTs content but different PEEK/TPI ratios were prepared. The composites with co‐continuous phase structure exhibited much better dielectric properties than those with sea–island structure. Then, PEEK/TPI/MWCNTs composites with the same PEEK/TPI ratio but various MWCNTs contents were prepared. The dielectric constant of the composite with 2 wt% MWCNTs reached 11306, which is because the formation of a co‐continuous phase structure benefited the mini‐capacitor network. Our results provide an effective method to develop high‐dielectric‐constant composites using the concept of double percolation. © 2015 Society of Chemical Industry     

Physico‐mechanical,thermal, and coating properties of composite materials prepared with epoxy resin/steel slag

The interest in using different solid waste as reinforcement in polymer composite preparation has increased considerably in recent years. Slag is one of the inorganic waste materials obtained from ore processing. In this work, epoxy composites filled with different percentages of slag were prepared. Physico‐mechanical, thermal, and coating properties of these composites were determined depending on the amount of filler, type of hardener, and polyethylene glycol (PEG) addition. X‐ray diffraction (XRD) studies were carried out to examine the compatibility of the filler and epoxy resin and XRD results showed good compatibility between two materials. The results of mechanical testing illustrated that hardness of the epoxy composites containing anhydride was partially higher than with Epamine PC17 in contrast to elongation at break. The tensile strength and Young modulus decreased with increasing filler amount. When compared to neat epoxy resin, corrosion, and adhesion properties of the composites with filler addition did not change significantly. The highest water sorption values were obtained for the epoxy composites with PEG addition. The composites hardened by anhydride had better thermal stability than the composites including Epamine PC17. POLYM. COMPOS., 38:1974–1981, 2017. © 2015 Society of Plastics Engineers