Improved thermal conductivity of epoxy composites using a hybrid multi-walled carbon nanotube/micro-SiC filler

By adding 6 wt% multi-walled carbon nanotubes (MWCNTs) or 71.7 wt% micro-SiC to an epoxy resin the thermal conductivities of the composites reached maxima that were respectively 2.9 and 20.7 times that of the epoxy alone. To further improve the thermal conductivity a method that partially replaces microfiller with nanofiller was used, and a thermal conductivity, 24.3 times that of the epoxy, was obtained with 5 wt% MWCNTs + 55 wt% micro-SiC.     

Effect of functionalization on the thermo-mechanical and electrical behavior of multi-wall carbon nanotube/epoxy composites

The effect of the functionalization of multi-wall carbon nanotubes (MWCNTs) on the structure, the mechanical and electrical properties of composites was investigated. Samples based on epoxy resin with different weight percentage of MWCNTs or COOH-functionalized carbon nanotubes (MWCNT–COOH) were prepared and characterized. Dynamic-mechanical thermal analysis shows that the storage modulus increases with the addition of MWCNTs, whereas a constant value or even a weak reduction was observed for functionalized nanotubes. Two phases were suggested in the composites with MWCNT–COOH, both by dynamic-mechanical properties and by water transport. Chemical functionalization of MWCNTs increases the compatibility with the epoxy matrix due to the formation of an interface with stronger interconnections. This, in turn, causes a significant decrease in the electrical conductivity of this type of composite with respect to the untreated MWCNTs which can be explained in terms of tunnelling resistance between interacting nanotubes.     

Effect of amino‐functionalization of multi‐walled carbon nanotubes on the dispersion with epoxy resin matrix

Amino‐functionalization of multiwalled carbon nanotubes (MWCNTs) was carried out by grafting triethylenetetramine (TETA) on the surfaces of MWCNTs through the acid–thionyl chloride way. The amino‐functionalized MWCNTs show improved compatibility with epoxy resin and, as a result, more homogenous dispersion in the matrix. The mechanical, optical, and thermal properties of the amino‐functionalized MWCNT/epoxy composites were also investigated. It was found that introducing the amino‐functionalized MWCNTs into epoxy resin greatly increased the charpy impact strength, glass transition temperature, and initial decomposing temperature of cured epoxy resin. In addition, introducing unfunctionalized MWCNTs into epoxy resin was found greatly depressing the light transmission properties, which would affirmatively confine the application of the MWCNTs/epoxy composites in the future, while much higher light transmittance than that of unfunctionalized MWCNTs/epoxy composites was found for amino‐functionalized MWCNTs/epoxy composites. SEM of the impact cross section and TEM of ultrathin film of the amino‐functionalized MWCNTs/epoxy composites showed that the amino‐functionalized MWCNTs were wetted well by epoxy matrix. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 97–104, 2006     

Improving thermal conductivity and shear strength of carbon nanotubes/epoxy composites via thiol‐ene click reaction

This study investigates the effect of the thiol‐ene click reaction on thermal conductivity and shear strength of the epoxy composites reinforced by various silane‐functionalized hybrids of sulfhydryl‐grafted multi‐walled carbon nanotubes (SH‐MWCNTs) and vinyl‐grafted MWCNTs (CC‐MWCNTs). The results of Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM) show that the sulfhydryl groups and vinyl groups are successfully grafted onto the surface of MWCNTs, after treatment of MWCNT with triethoxyvinylsilane and 3‐mercaptopropyltrimethoxysilane, respectively. Scanning electron microscopy (SEM), HotDisk thermal constant analyzer (HotDisk), optical microscope, and differential scanning calorimetry (DSC) are used to characterize the resultant composites. It is demonstrated that the hybrid of 75 wt % SH‐MWCNTs and 25 wt % CC‐MWCNTs has better dispersion and stability in epoxy matrix, and shows a stronger synergistic effect in improving the thermal conductivity of epoxy composite via the thiol‐ene click reaction with 2,2′‐azobis(2‐methylpropionitrile) as thermal initiator. Furthermore, the tensile shear strength results of MWCNT/epoxy composites and the optical microscopy photographs of shear failure section indicate that the composite with the hybrid MWCNTs has higher shear strength than that with raw MWCNTs. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44579.     

Effect of functionalized MWCNTs on the thermo-mechanical properties of poly(5-ethylidene-2-norbornene) composites produced by ring-opening metathesis polymerization

Functionalized multiwalled carbon nanotubes (MWCNTs) reinforced poly(5-ethylidene-2-norbornene (ENB)) composites have been fabricated via ring-opening metathesis polymerization. Verification of covalent bond formation between the functionalized carbon nanotubes and the polyENB matrix was demonstrated by solvent exposure followed by thermal gravimetry. The tensile toughness of the composites increased by 300% with dramatic morphological changes on the resulting fracture surfaces when just 0.8 wt% norbornene-functionalized MWCNTs (f-MWCNTs) were added to the polymer. A slight increase of glass-transition temperature was observed by dynamic mechanical analysis compared to a decreased value with unfunctionalized MWCNTs.     

环氧树脂/改性碳纳米管复合材料的导热性能

采用硝酸氧化开口、银（Ag）填充和1,6己二胺接枝3种方法对多壁碳纳米管（MWCNTs）进行了改性,并用熔融共混法分别制备了各环氧树脂/改性MWCNTs纳米复合材料,通过扫描电子显微镜、透射电子显微镜、红外光谱等对复合材料的性能进行了测试。结果表明,各改性MWCNTs在环氧树脂中分散均匀,与树脂结合紧密无空隙;复合材料的热导率显著提高,其中改性MWCNTs含量为2.2 %（质量分数,下同）的开口多壁碳纳米管（Opened MWCNTs）和Ag填充多壁碳纳米管（Ag-filled MWCNTs）复合材料的热导率均达到0.20 W/（m·K）,比纯环氧树脂提高了33.3 %。     

Noncovalent functionalization of carbon nanotube using poly(vinylcarbazole)‐based compatibilizer for reinforcement and conductivity improvement in epoxy composite

A new compatibilizer [P(GMA‐co‐VCz) copolymer] containing carbazole moiety and reactive epoxide group, which can functionalize multiwalled carbon nanotubes (MWCNTs) for making superior epoxy composites, was prepared by a simple one‐pot free radical polymerization. The designed compatibilizer could noncovalently functionalize multiwalled carbon nanotube (MWCNTs) via π‐π interaction as evidenced from fluorescence, Raman, and FTIR spectra analysis, and efficiently disperse MWCNTs in organic solvents. TEM images suggest a good wrapping of P(GMA‐co‐VCz) on MWCNTs surface. P(GMA‐co‐VCz) functionalized MWCNTs were more homogeneously dispersed in epoxy matrix than the case without compatibilizer, indicating that the compatibilizer improves the compatibility between MWCNTs and epoxy resin. In addition, the presence of epoxide groups in compatibilizer could generate covalent bonds with the epoxy matrix and improve the interface interaction between MWCNTs and epoxy matrix. As a result, mechanical and electrical properties of the epoxy composites with compatibilizer were largely improved as compared with those of composites without compatibilizer. The addition of as little as 0.15 wt % of MWCNTs to epoxy matrix affords a great increase of 40% in storage modulus and 52.5% in elongation at break. Furthermore, a sharp decrease of almost 9 orders of magnitude in volume resistivity of epoxy composite is observed. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45022.     

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     

Rheological and electrical properties of polypropylene composites containing functionalized multi-walled carbon nanotubes and compatibilizers

Multi-walled carbon nanotubes (MWCNTs) were chemically functionalized through acid, amine, and heat treatments. These were used in the manufacture of composites using polypropylene (PP) as matrix and two types of compatibilizers, maleic anhydride grafted polypropylene (MA-g-PP) and maleic anhydride grafted styrene-ethylene/butylene-styrene (MA-g-SEBS). PP/MWCNT composites filled with modified MWCNTs and compatibilizers were prepared by melt compounding with a twin-screw extruder and were evaluated to understand the effect of dispersion and interfacial interaction on the morphological, rheological, and electrical properties of the composite. When heat treated MWCNTs and compatibilizers were added to the composite, three dimensional network structures were generated through nanotube-nanotube and nanotube-matrix interactions resulting in percolation. Electrical conductivity was dramatically increased when the heat treated MWCNTs were added to the composite and was increased further with the addition of MA-g-SEBS compatibilizer.     

EP/GNs/MWCNTs复合材料的导热性能

以多壁碳纳米管(MWCNTs)和石墨烯纳米微片(GNs)为导热填料,环氧树脂(EP)为基体采用溶剂和超声分散法,制备了EP/GNs/MWCNTs导热复合材料,并与EP/MWCNTs及EP/GNs复合材料的导热性能进行了对比。采用透射电子显微镜观察其微观结构,采用Hot Disk热导率测试仪测试其导热性能,采用差示扫描量热法和热重分析仪测试其耐热性及热稳定性。结果表明,MWCNTs和GNs共同作为EP导热填料时,相比于单组分填料(MWCNTs或GNs)更易形成导热网络;EP的热导率、玻璃化转变温度(Tg)和热分解温度均随着MWCNTs或GNs含量的增加而提高,其中,GNs更有利于提高EP的热导率和热分解温度,MWCNTs更有利于提高EP的Tg。在相同的导热填料含量下,相对于其中的任一单一填料,MWCNTs/GNs共同作用时,对热导率的提高有更显著的效果,且随着其中GNs比例的增加,热导率逐渐增大。当GNs和MWCNTs的体积分数分别为0.6%和0.4%时,EP/GNs/MWCNTs复合材料的热导率、Tg和起始分解温度分别为0.565 W/(m·K),152℃和316℃,分别比纯EP提高了132.5%,34.5%和8.2%。     

Thermal conductivity and dynamic mechanical property of glycidyl methacrylate‐grafted multiwalled carbon nanotube/epoxy composites

The well dispersed multiwalled carbon nanotube (MWCNT)/epoxy composites were prepared by functionalization of the MWCNT surfaces with glycidyl methacrylate (GMA). The morphology and thermal properties of the epoxy nanocomposites were investigated and compared with the surface characteristics of MWCNTs. GMA‐grafted MWCNTs improved the dispersion and interfacial adhesion in epoxy resin, and enhanced the network structure. The storage modulus of 3 phr GMA‐MWCNTs/epoxy composites at 50°C increased from 0.32 GPa to 2.87 GPa (enhanced by 799%) and the increased tanδ from 50.5°C to 61.7°C (increased by 11.2°C) comparing with neat epoxy resin, respectively. Furthermore, the thermal conductivity of 3 phr GMA‐MWCNTs/epoxy composite is increased by 183%, from 0.2042 W/mK (neat epoxy) to 0.5781 W/mK. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Functionalized multiwalled carbon nanotubes in mild polyphosphoric acid/phosphorous pentoxide/phosphoric acid and their composites with epoxy resin

Multiwalled carbon nanotubes (MWCNTs) were functionalized through “Friedel‐Craft” acylation with 1,3,5‐Benzenetricarboxylic acid (BTC) in mild polyphosphoric acid (PPA)/ phosphorus pentoxide (P₂O₅)/phosphoric acid (PA) medium at 130°C. The high‐resolution transmission electron microscopy, Raman spectra, and X‐ray photoelectron spectra (XPS) were used to characterize the surface microstructure nature of functionalized MWCNTs in optimum PPA/P₂O₅/PA medium. The thermostability of functionalized MWCNTs was characterized by thermogravimetric analysis. The maximum rate of weight loss temperature increased as compared with pristine MWCNTs. The dispersion properties of MWCNTs and the flexural properties of the MWCNTs/epoxy composites affected by MWCNTs functionalization are investigated. It is demonstrated that the functionalized MWCNTs exhibit much better dispersability than pristine MWCNTs. The attached BTC molecules arising from the functionalization effectively improved interfacial adhesion between the epoxy resin and functionalized MWCNTs through covalent bonds, resulting in improved flexural properties compared with those without functionalization. POLYM. COMPOS., 35:1275–1284, 2014. © 2013 Society of Plastics Engineers     

碳纳米管-膨胀石墨/环氧树脂复合材料的导热性能

在环氧树脂中添加多壁碳纳米管和膨胀石墨作为填料,以提高环氧树脂的导热性能. 结果表明,添加0.5wt%多壁碳纳米管时,环氧树脂的最佳导热系数为0.3448 W/(m?K),比不添加时提高30%;添加0.75wt%羧基改性多壁碳纳米管时,环氧树脂的最佳导热系数为0.3813 W/(m?K),比添不加时提高40%;同时添加多壁碳纳米管和膨胀石墨后,环氧树脂导热系数可进一步提高到0.4039 W/(m?K),表明在环氧树脂中添加混合填料,二者可在环氧树脂中形成有效的导热网络,能进一步提高聚合物的导热性能.     

碳纳米管材料导热性能的实验研究

本文对碳纳米管与环氧树脂(Epoxy-EP)复合材料的导热性能进行了定量的研究,探索了CNTs/EP复合材料的制备方法,运用Hotdisk热常数分析仪研究了CNTs/EP复合材料的导热系数;利用CNTs/EP两相复合材料的导热理论模型得到了室温下单壁碳纳米管(Single-Wall Carbon Nanotubes-SWCNTs)的导热系数为3980 W/(m.K),双壁碳纳米管的导热系数(Double-Wall Carbon Nanotubes-DWCNTs)为3580 W/(m.K),以及多壁碳纳米管(Multi-Wall Carbon Nanotubes-MWCNTs)的导热系数为2860 W/(m.K)。     

Enhancement in mechanical properties of multiwalled carbon nanotube‐reinforced epoxy composites: Crosslinking of the reinforcement with the matrix via diamines

In this study, the effect of diamine molecular structure, attached to the multiwalled carbon nanotubes (MWCNTs), on the interfacial interactions of the MWCNTs and the epoxy matrix was studied. Pristine MWCNTs were successfully functionalized with multiple aliphatic and aromatic diamines. It has been found that, compared to aliphatic molecules, aromatic diamines can yield higher functionalization degree, due to higher activity and longer half‐life of aromatic intermediates. However, at the same functionalization degree, the aliphatic ligands were more successful in reacting with epoxy chains and forming covalent bonds between the MWCNTs and the matrix. Considerable improvements were achieved in the mechanical properties of functionalized MWCNT‐reinforced epoxy composites in comparison with the pristine MWCNT‐reinforced composites. Fractography observations revealed distinct differences in the failure modes of reinforced composites after functionalization of the MWCNTs with diamines. POLYM. ENG. SCI., 59:1905–1910, 2019. © 2019 Society of Plastics Engineers     

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.     

Improved thermal conductivity for chemically functionalized exfoliated graphite/epoxy composites

Chemically functionalized exfoliated graphite-filled epoxy composites were prepared with load levels from 2% to 20% by weight. The viscosities of the composites having load levels >4% by weight were over the processing window for the vacuum-assisted resin transfer molding process. Wide-angle X-ray diffraction revealed a rhombohedral carbon structure in the filler. Enhanced interaction between the epoxy and the graphite filler was evidenced by an improvement in the rubber modulus for the chemically functionalized graphite/epoxy composites. The thermal and electrical properties of the nanoparticle-filled epoxy composites were measured. The electrical property of the chemically functionalized graphite/epoxy composite deteriorated. Thermal conductivity of the chemically functionalized graphite/epoxy composite, however, increased by 28-fold over the pure epoxy resin at the 20% by-weight load level, increasing from 0.2 to 5.8 W/m K.     

The effect of a doubly modified carbon nanotube derivative on the microstructure of epoxy resin

The surface of multi wall carbon nanotubes (MWCNTs) was first covalently functionalized with oleyl amine and then non-covalently wrapped with polycarbosilane (PCS). The hybrid functional groups were chosen to introduce different features in the MWCNTs properties. For covalent functionalization a long chain unsaturated aliphatic amine was used to simultaneously achieve the dissociation of MWCNT bundles along with the dispersion and interaction with the host matrix using the amide functionality and double bond. On the other hand, a thermally stable polymer was selected which can interact with both resin and glass fabric to promote interfacial adhesion. This hybrid doubly modified MWCNT is thus possesses duel advantages in glass fiber based epoxy composite. The pristine, covalent, noncovalent and covalent-noncovalent doubly modified MWCNT systems were used to study the viscoelastic behavior and interactions of functionalized MWCNTs in the matrix above and below the glass transition temperature of the matrix. The PCS coating on the MWCNTs is amorphous and thermally insulating whereas the nanotube is highly graphitized and thermally conducting. This contrasting behavior provides us to insight into the temperature dependant resin microstructure and curing thermodynamics of epoxy resin in the presence of MWCNTs.     

The effects of triethylenetetramine grafting of multi‐walled carbon nanotubes on its dispersion,filler‐matrix interfacial interaction and the thermal properties of epoxy nanocomposites

This study describes the influence of triethylenetetramine (TETA) grafting of multi‐walled carbon nanotubes (MWCNTs) on the dispersion state, interfacial interaction, and thermal properties of epoxy nanocomposites. MWCNTs were first treated by a 3:1 (v/v) mixture of concentrated H₂SO₄/HNO₃, and then TETA grafting was performed. Chemically grafted MWCNT/bisphenol‐A glycidol ether epoxy resin/2‐ethyl‐4‐methylimidazole nanocomposites were prepared. TETA grafting could establish the connection of MWCNTs to the epoxy matrix and transform the smooth and nonreactive MWCNT surface into a hybrid material that possesses the characteristics of both MWCNTs and TETA, which facilitates homogeneous dispersion of MWCNTs and improves nanotube‐epoxy interfacial interaction. Therefore, the impact property, glass transition temperature, thermal stability, and thermal conductivity of epoxy nanocomposites are enhanced. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Physical properties of phenol-anchored multiwall carbon nanotube/epoxy nanocomposite

Surface functionalization of multiwall carbon nanotubes (MWCNTs) was carried out by introducing a ylide group containing anchored phenol structures. Epoxy nanocomposites filled with modified and pristine carbon nanotubes were prepared, and their mechanical, electrical, and thermal properties were evaluated. Mechanical properties such as tensile strengths and Young’s moduli of the epoxy nanocomposites increased significantly with the addition of the modified MWCNTs compared to the pristine MWCNTs, due to the strong interaction between the modified MWCNTs and the epoxy matrix. Scanning electron microscopy of the fractured epoxy systems revealed that the functionalized MWCNTs were finely dispersed in the matrix, as opposed to the pristine carbon nanotubes. The epoxy/functionalized MWCNT nanocomposite had a lower surface electrical resistance than the epoxy/pristine MWCNT nanocomposite, confirming the effect of functionalization.