Flammability and thermal properties of epoxy/glass/MWNT Composites

The aim f this work is to study the effect of nanotubes on flammability properties of epoxy/glass composites. Multiwalled carbon nanotubes (MWNT) and its functionalized derivative (amino functionalized nanotubes) were incorporated into epoxy resin. To disperse MWNTs in the epoxy resin, different ways were employed. Microscopic observations showed that, the best dispersion state was gained by using ultrasonication method and high shear flow simultaneously. Thermal resistance of cured epoxy resins containing various amounts of nanotubes (0.25–0.7 wt %), was investigated by thermo gravimetric analysis (TGA). Introducing MWNTs and amino‐MWNTs to samples increased the initial thermal decomposition temperature for about 32 and 37°C, respectively. LOI measurements of composite samples showed an increase up to 32. Cone calorimetry test was carried out on epoxy/glass and epoxy/glass containing 0.5% MWNT. The results showed that, introducing 0.5% MWNTs decreases maximum average rate of heat emission for about 26%. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39849.     

Effects of nanotube modification on the dielectric behaviors and mechanical properties of multiwall carbon nanotubes/epoxy composites

Multiwall carbon nanotubes (MWNTs) were modified by three methods, namely, oxidizing the tubes and opening both ends, filling the tubes with Ag, and grafting the tubes with hexamethylene diamine. Modified MWNTs/epoxy composites were prepared by melt‐mixing epoxy resin with the tubes. Transmission electron microscope images showed that the modified MWNTs can be dispersed in the epoxy matrix homogeneously. The dielectric behaviors and mechanical properties of the composites were investigated. The dielectric and mechanical properties of the modified MWNTs/epoxy composites were considerably improved compared with those of the epoxy matrix. The tensile strengths of the Ag‐filled, opened, and grafted MWNTs composites at the same filler content of 1.1 wt% were higher by ～30.5%, 35.6%, and 27.4%, respectively, than that of neat epoxy. The Izod notched impact strength of the grafted MWNTs/epoxy composite with filler content of 1.1 wt% was approximately four times higher than that of neat epoxy. A dielectric constant of ～150 of the composite with 1.1 wt% Ag‐filled nanotubes was observed in the low‐frequency range, which was ～40 times higher than that of the epoxy matrix. The proper modification of nanotubes provides a way to improve the properties of the polymer‐based composites. POLYM. ENG. SCI., 2013. © 2012 Society of Plastics Engineers     

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     

Effect of crosslink density on thermal conductivity of epoxy/carbon nanotube nanocomposites

The effect of the polymeric crosslink density on the thermal conductivity of an epoxy nanocomposite was investigated by adding two different diamine‐functionalized multiwalled carbon nanotubes (diamine‐MWNTs) to the epoxy resin as co‐curing agents and conducting fillers. Tetramethylenediamine (TMDA)‐MWNTs resulted in an epoxy nanocomposite with a higher crosslink density than octamethylenediamine (OMDA)‐MWNTs. Interestingly, epoxy/TMDA‐MWNT nanocomposites under 1.5 wt % nanotube concentration, showed a higher thermal conductivity than an epoxy/OMDA‐MWNT nanocomposite with the same concentration of nanotubes. In contrast, for higher diamine‐MWNT concentrations (over 2.0 wt %), the thermal conductivity of the epoxy/OMDA‐MWNT nanocomposite was higher than that with TMDA‐MWNTs. We observed that for low MWNT concentrations, where a percolating network was not formed, a high crosslink density enhanced the thermal conductivity via phonon transport. However, for high MWNT concentrations, a high crosslink density hinders the formation of a percolating network and lowers the thermal conductivity. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44253.     

Fabrication and characterization of the mechanical properties of multi-walled carbon nanotube-reinforced epoxy resins by e-beam irradiation

In this study, the multi-walled carbon nanotubes (MWNT) were reinforced to epoxy resin as fabrication of epoxy/MWNT nanocomposites by electron beam (e-beam) curing. An attempt is made to disperse MWNT into diglycidyl ether of bisphenol A (DGEBA) as epoxy resins, using triarylsulfonium hexafluoroantimonate (TASHFA) as an initiator. E-beam irradiation effect on the curing of the epoxy resin was investigated in oxygen and nitrogen atmospheres at room temperature. The flexural modulus was measured by a universal testing machine (UTM). Here, the flexural modulus factor exhibits an upper limit at 0.3 wt% MWNT. The dynamic mechanical and thermal properties of the irradiated epoxy resins were characterized using DMA, DSC and TGA machines. DMA curves of the storage modulus revealed an increase with an increasing MWNT content and radiation dose. However, the T_g curve decreased as a function of the increasing MWNT content and radiation dose. The thermal properties of the TGA and DSC data were improved by increasing the content of the MWNT and the radiation dose. Likewise, the thermal properties were stabilized by increasing the amount of initiator and irradiating the resins in a nitrogen atmosphere.     

碳纳米管／环氧树脂复合体系研究

采用熔融混合法,利用超声分散制备了碳纳米管／环氧树脂纳米复合材料。研究了羟基化碳纳米管的添加量对复合材料的反应活性的影响;同时测试了碳纳米管／环氧树脂纳米复合材料的弯曲性能和电性能,并利用透射电镜对碳纳米管在复合材料中的微观结构进行了表征。结果表明：碳纳米管使复合材料的反应活性有所提高;当碳纳米管含量为1％时,碳纳米管／环氧树脂复合材料的弯曲强度和弯曲模量分别由纯体系的143．32MPa和3563．76MPa提高到155．79MPa和3690．45MPa,碳纳米管在环氧树脂基体中呈单根分散。碳纳米管使复合材料的体积电阻率和表面电阻率下降2个数量级。     

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     

Improvement of dispersion of carbon nanotubes in epoxy resin through pyrogallol functionalization

Multiwalled carbon nanotubes (MWNTs) were functionalized with pyrogallol. The functionalized MWNTs were well‐dispersed in the epoxy/curing agent/ethanol solution, as demonstrated by UV‐vis spectra and optical micrographs. Epoxy resin/MWNTs composites were prepared via solution mixing method. The cure behavior was characterized using differential scanning calorimetry. Pyrogallol‐functionalized carbon nanotubes (CNTs) reacted with the epoxy through the mediation reaction of pyrogallol with the curing agent, leading to the interfacial bonding between the functionalized carbon nanotubes (CNTs) and the resin matrix. Due to the excellent dispersion and interfacial bonding, the mechanical strength and electrical conductivity of the epoxy resin/CNTs composites have been improved. POLYM. ENG. SCI. 56:1079–1085, 2016. © 2016 Society of Plastics Engineers     

High electrical conductivity of nylon 6 composites obtained with hybrid multiwalled carbon nanotube/carbon fiber fillers

The synergetic effect of multiwalled carbon nanotubes (MWNTs) and carbon fibers (CFs) in enhancing the electrical conductivity of nylon 6 (PA6) composites was investigated. To improve the compatibility between the fillers and the PA6 resin, we grafted γ‐aminopropyltriethoxy silane (KH‐550) onto the MWNTs and CFs after carboxyl groups were generated on their surface by chemical oxidation with nitric acid. Fourier transform infrared spectroscopy and thermogravimetric analysis proved that the KH‐550 molecules were successfully grafted onto the surface of the MWNTs and CFs. Scanning electron microscopy and optical microscopy showed that the obtained modified fillers reduced the aggregation of fillers and resulted in better dispersion and interfacial compatibility. We found that the electrical percolation threshold of the MWNT/PA6 and CF/PA6 composites occurred when the volume fraction of the fillers were 4 and 5%, respectively. The MWNT/CF hybrid‐filler system exhibited a remarkable synergetic effect on the electrically conductive networks. The MWNT/7% CF hybrid‐filler system appeared to show a second percolation when the MWNT volume fraction was above 4% and a volume resistivity reduction of two orders of magnitude compared with the MWNT/PA6 system. The mechanical properties of different types of PA6 composites with variation in the filler volume content were also studied. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40923.     

High thermal conductive m‐xylylenediamine functionalized multiwall carbon nanotubes/epoxy resin composites

In this study, multiwall carbon nanotubes (MWNTs) functionalized by m‐xylylenediamine is used as thermal conductive fillers to improve their dispersibility in epoxy resin and the thermal conductivity of the MWNTs/bisphenol‐A glycidol ether epoxy resin composites. Functionalization with amine groups of MWNTs is achieved after such steps as carboxylation, acylation and amidation. The thermal conductivity, impact strength, flexural strength, and fracture surfaces of MWNTs/epoxy composites are investigated with different MWNTs. The results show that m‐xylylenediamine is successfully grafted onto the surface of the MWNTs and the mass fraction of the organic molecules grafted onto MWNTs is about 20 wt %. The thermal conductivity of MWNTs/epoxy composites is further enhanced to 1.236 W/mK with 2 wt % m‐MWNTs. When the content of m‐MWNTs is 1.5 wt %, the impact strength and flexural strength of the composites are 25.85 KJ/m², 128.1 MPa, respectively. Scanning electron microscope (SEM) results show that the fracture pattern of composites is changed from brittle fracture to ductile fracture. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41255.     

多壁碳纳米管/环氧树脂纳米复合材料的固化动力学研究

采用熔融混合法向低粘度的环氧树脂中添加适量的多壁碳纳米管,制备新型纳米复合材料,并采用傅里叶变换红外光谱仪(FT-IR)测试转化率,采用差示扫描量热法(DSC)研究多壁碳纳米管/环氧树脂复合体系的固化动力学,并对纳米复合材料的力学性能进行研究。结果表明:多壁碳纳米管加入环氧树脂复合体系后,对固化反应有催化作用,固化反应速率增大,转化率提高,而复合体系的力学性能却有所下降,玻璃化转变温度变化不大。     

Morphology and mechanical and electrical properties of oriented PVA-VGCF and PVA-MWNT composites

The composites poly(vinyl alcohol) (PVA) and vapor growth carbon fiber (VGCFs) and multi wall carbon nanotubes (MWNTs) were prepared by gelation/crystallization from the mixture of dimethyl sulfoxide (DMSO) and water (H₂O). The composite films were elongated to 5-10-fold uniaxially. The mechanical properties of PVA composites were improved significantly by introduction of VGCFs and MWNTs and also by the orientation of fillers. Compared to VGCFs, MWNTs was more effective to improve the electric conductivity of the composites because of its network structure. The change in the electrical conductivity for the PVA/MWNT composites containing 5 wt% MWNT was independent of the draw ratio up to eight-fold indicating no disruption of the network formation. A certain high level of filler content was proved to be necessary for the promotion of both mechanical and electrical properties in oriented composite.     

Electrical conductivity and microwave absorbing properties of nickel‐coated multiwalled carbon nanotubes/poly(phthalazinone ether sulfone ketone)s composites

Nickel‐coated multiwalled carbon nanotubes (Ni‐MWNT) were prepared by electroless deposition with ultrasonic vibrations. The morphologies and components were characterized by scanning electron microscope and energy dispersive spectroscopy. Two types of fillers, multiwalled carbon nanotubes (MWNT) and Ni‐MWNT, were blended with poly(phthalazinone ether sulfone ketone)s (PPESK) by the solution‐mixing method, respectively. The electrical conductivity and microwave absorbing properties of the composites were investigated. The results show that Ni‐MWNT/PPESK composites have relatively lower electrical resistivity values than MWNT/PPESK, and in both cases the decrease in electrical resistivity indicates a similar percolation transition behavior in the same MWNT content region. Moreover, as MWNT loading is 5 parts per hundred parts of resin (phr), Ni‐MWNT/PPESK composite has the wider frequency region (9.5–13.5 GHz) of the reflection loss (RL) less than ?10 dB and the lower minimum value of RL (?27.5 dB) compared with MWNT/PPESK. The better microwave absorption properties can be attributed to the improved dielectric and magnetic properties of the fillers. A good correlation between electrical conductivity and microwave absorption was found for MWNT/PPESK composites. In addition, tensile test and thermogravimetric analysis indicate that introducing Ni‐MWNT into PPESK is favorable for the improvement of the mechanical properties and high temperature stability of the composites. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

The dynamic mechanical analysis of epoxy–copper powder composites using azole compounds as coupling agents

The dynamic mechanical properties of cured epoxy resin have been studied in which copper powder treated or untreated with azole compounds was used as fillers. The untreated fillers do not shift the glass transition temperature of the matrix polymer of the composites, whereas the storage modulus rises with increasing content of fillers. The application of azole compounds as coupling agents, which could react with both copper and epoxy resin, extended the polymer–filler interactions. The composite filled with copper powder treated with benzotriazole shows a strong reinforcement effect and high resistance to moisture.     

Multiwalled carbon nanotube polymer composites: Synthesis and characterization of thin films

The aim of this article was to elucidate the basic relationships between processing conditions and the mechanical and electrical properties of multiwalled carbon nanotube reinforced polymer composites. In conventional chopped fiber reinforced polymer composites, uniform distributions of fibers throughout the matrix are critical to producing materials with superior physical properties. Previous methods have dispersed carbon nanotubes by aggressive chemical modification of the nanotubes or by the use of a surfactant prior to dispersion. 1 , 2 Here, ultrasonic energy was used to uniformly disperse multiwalled nanotubes (MWNTs) in solutions and to incorporate them into composites without chemical pretreatment. Polystyrene (PS) solutions containing MWNTs were cast and spun to yield thin film MWNT composites. The rheology of PS/MWNT suspensions was modeled using the Carreau equation. MWNTs were found to align at the shear rates generated by the spin casting process. The tensile modulus and strain to failure of samples compared well to classical micromechanical models, increasing with MWNT loading. The composite films showed lower strains at the yield stress than neat PS films. The presence of MWNTs at 2.5 vol % fraction approximately doubles the tensile modulus, and transforms the film from insulating to conductive (surface resistivity, ρ, approaching 10³ Ω/□). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2660–2669, 2002     

Dopamine modification of multiwalled carbon nanotubes and its influences on the thermal,mechanical, and tribological properties of epoxy resin composites

A functionalization process with dopamine on multiwalled carbon nanotubes (MWNTs) has been carried out in order to enhance the tribological properties of MWNTs/epoxy resin (EP) composites. Dopamine modification is of signality for the performance of MWNTs/EP composites. The hardness and flexural strength of the composites were significantly improved with the incorporation of dopamine modified MWNTs, owning to the enhanced interfacial bonding between MWNTs and EP. Meanwhile, the thermal characterizations indicated that dopamine played an important role in improving the thermal stability of MWNTs/EP composites. More importantly, the friction and wear properties of dopamine modified MWNTs/EP composites were enhanced considerably and its wear rate was 85.8% lower than that of pure EP. Dopamine modified MWNTs were linked with the matrix by strong covalent bond to form a great network structure and impeded the movement of polymer molecule chains in the composites. Then the friction load transmitted efficiently through the network structure and the plastic deformation was restrained as well as the initiation and growth of cracks on the worn surfaces. POLYM. COMPOS., 38:116–125, 2017. © 2015 Society of Plastics Engineers     

Improving delamination resistance of carbon fiber reinforced polymeric composite by interface engineering using carbonaceous nanofillers through electrophoretic deposition: An assessment at different in-service temperatures

In this article, modification of carbon fiber surface by carbon based nanofillers (multi-walled carbon nanotubes [CNT], carbon nanofibers, and multi-layered graphene) has been achieved by electrophoretic deposition technique to improve its interfacial bonding with epoxy matrix, with a target to improve the mechanical performance of carbon fiber reinforced polymer composites. Flexural and short beam shear properties of the composites were studied at extreme temperature conditions; in-situ cryo, room and elevated temperature (−196, 30, and 120°C respectively). Laminate reinforced with CNT grafted carbon fibers exhibited highest delamination resistance with maximum improvement in flexural strength as well as in inter-laminar shear strength (ILSS) among all the carbon fiber reinforced epoxy (CE) composites at all in-situ temperatures. CNT modified CE composite showed increment of 9% in flexural strength and 17.43% in ILSS when compared to that of unmodified CE composite at room temperature (30°C). Thermomechanical properties were investigated using dynamic mechanical analysis. Fractography was also carried out to study different modes of failure of the composites.     

Effect of different carbon fillers on the properties of PP composites: Comparison of carbon black with multiwalled carbon nanotubes

Polypropylene (PP)/carbon composites were prepared via melt blending PP with carbon fillers, including multiwalled carbon nanotubes (MWNTs) and carbon black (CB). Field‐emission scanning electron microscopy was used to research the morphology and dispersion of fillers in the PP matrix. The electrical properties, mechanical properties, and crystallization behaviors of PP/carbon composites were also investigated. The results show that the influence of MWNTs on the properties of PP composites is different with CB, which can be ascribed to the structure and aspect ratio difference between MWNTs and CB. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:4823–4830, 2006     

In situ synthesis and characterization of poly(2,5-benzoxazole)/multiwalled carbon nanotubes composites

This article reports the synthesis of poly(2,5-benzoxazole)/multiwalled carbon nanotubes (ABPBO/MWNT) composites by in situ polycondensation and their chemical and physical properties. The functional groups yielded from the surface modification of MWNTs by hydrochloric acids have been demonstrated to participate in the polymerization and thus led to the composites with homogenous dispersion of carbon nanotubes. The chemical structures and morphology of the afforded polymer composites have been fully characterized by FTIR, WAXD, UV-vis, TGA and SEM. The ABPBO/MWNT composites exhibit excellent thermal stability and greatly improved mechanical properties. The tensile modulus and tensile strength of the composites are 47% and 83%, respectively, higher than those of the polymer matrix. The dielectric constant of the composites is also significantly enhanced from 4 of the polymer matrix to 65 with the incorporation of 5 wt% MWNTs.     

The Curing Behavior and Properties of Diglycidyl Ether of 4,4′-Bis(4-hydroxybenzoyloxy)-3,3′,5,5′-tetramethylbiphenyl and its Composites with Multi-Wall Carbon Nanotubes

The curing system of a liquid crystalline epoxy monomer, diglycidyl ether of 4,4′-bis(4-hydroxybenzoyloxy)-3,3′,5,5′-tetramethylbiphenyl (DGE-BHBTMBP), and curing agent diaminodiphenylsulfon (DDS) was investigated by means of differential scanning calorimetry (DSC). Physical properties of the cured polymer and its composites with carbon nanotubes were evaluated with dynamic mechanical thermal analysis (DMA). Test of transmission electron microscopy (TEM) showed that oxidated multi-wall carbon nanotubes (OX-MWNT) performed a better dispersion in the cured polymer than untreated MWNT did. The storage modulus of the cured polymer containing OX-MWNT increased, while that containing untreated MWNT decreased. The results also showed that the T_g decreased when the MWNT was filled.