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)。     

Electrical,rheological and electromagnetic interference shielding properties of thermoplastic polyurethane/carbon nanotube composites

Electrically conducting rubbery composites based on thermoplastic polyurethane (TPU) and carbon nanotubes (CNTs) were prepared through melt blending using a torque rheometer equipped with a mixing chamber. The electrical conductivity, morphology, rheological properties and electromagnetic interference shielding effectiveness (EMI SE) of the TPU/CNT composites were evaluated and also compared with those of carbon black (CB)‐filled TPU composites prepared under the same processing conditions. For both polymer systems, the insulator–conductor transition was very sharp and the electrical percolation threshold at room temperature was at CNT and CB contents of about 1.0 and 1.7 wt%, respectively. The EMI SE over the X‐band frequency range (8–12 GHz) for TPU/CNT and TPU/CB composites was investigated as a function of filler content. EMI SE and electrical conductivity increased with increasing amount of conductive filler, due to the formation of conductive pathways in the TPU matrix. TPU/CNT composites displayed higher electrical conductivity and EMI SE than TPU/CB composites with similar conductive filler content. EMI SE values found for TPU/CNT and TPU/CB composites containing 10 and 15 wt% conductive fillers, respectively, were in the range ?22 to ?20 dB, indicating that these composites are promising candidates for shielding applications. © 2013 Society of Chemical Industry     

Effects of flake graphite on property optimisation in thermal conductive composites based on polyamide 66

In this study, in order to improve the thermal conductivity of polyamide 66(PA66), PA66 composites filled with flake graphite (FG) were prepared by twin-screw extruder. Effects of filler content, particle size and particle size mixing on thermal conductivity, mechanical and rheological properties of the composites were investigated. The results showed that as FG content increased from 0 to 50 wt-%, thermal conductivity of the composites filled with 100 μm FG gradually increased, whereas mechanical properties and rheological properties decreased. At 50 wt-% loading, thermal conductivity reached 3.07 W/(m K). With the increase of particle size, thermal conductivity and rheological properties of the composites improved, but mechanical properties increased first and then decreased. The composite filled with 100 μm FG had relatively optimal mechanical properties. Particle size mixing can improve thermal conductivity and the maximum value was achieved in the 1:2 mass ratio of 20 and 100 μm particles.     

Simultaneous improvement of thermal conductivity and mechanical properties for mechanically mixed ABS/h-BN composites by using small amounts of hyperbranched polymer additives

Recently, thermal interface materials (TIMs) are in great demands for modern electronics. For mechanically mixed polymer composite TIMs, the thermal conductivity and the mechanical properties are generally lower than expected values due to the sharply increased viscosity and poor filler dispersion. This work shows that addition of a small amount of polyester-based hyperbranched polymer (HBP) avoided the trade-off in mechanically mixed ABS/hexagonal boron nitride (h-BN) composites. After adding 0.5 wt% HBP, the maximum h-BN content in the composites increased from 50 to 60 wt%. The out-of-plane, in-plane thermal conductivity, and tensile strength of ABS/h-BN with 50 wt% h-BN were 0.408, 0.517 W/mK, and 18 MPa, respectively, and were increased to 0.729, 0.847 W/mK, and 32 MPa by adding 0.5 wt% HBP, while 0.972, 1.12 W/mK, and 29.5 MPa were achieved for ABS/h-BN/HBP with 60 wt% h-BN. The morphological and rheological results proved that these enhancements are due to the improved h-BN dispersion by decreasing viscosity of composites during mixing. Theoretical modeling based on the modified effective medium theory confirmed such results and showed that the interfacial thermal resistance also decreased slightly. Thus, this work demonstrates a facile and scalable method for simultaneously improving the thermal conductivity and mechanical properties of thermoplastic-based TIMs.     

Graphene nanoplate and multiwall carbon nanotube–embedded polycarbonate hybrid composites: High electromagnetic interference shielding with low percolation threshold

This study has reported the preparation of polycarbonate (PC)/graphene nanoplate (GNP)/multiwall carbon nanotube (MWCNT) hybrid composite by simple melt mixing method of PC with GNP and MWCNT at 330°C above the processing temperature of the PC (processing temperature is 280°C) followed by compression molding. Through optimizing the ratio of (GNP/MWCNT) in the composites, high electromagnetic interference shielding effectiveness (EMI SE) value (∼21.6 dB) was achieved at low (4 wt%) loading of (GNP/MWCNT) and electrical conductivity of ≈6.84 × 10⁻⁵ S.cm⁻¹ was achieved at 0.3 wt% (GNP/MWCNT) loading with low percolation threshold (≈0.072 wt%). The high temperature melt mixing of PC with nanofillers lowers the melt viscosity of the PC that has helped for better dispersion of the GNPs and MWCNTs in the PC matrix and plays a key factor for achieving high EMI shielding value and high electrical conductivity with low percolation threshold than ever reported in PC/MWCNT or PC/graphene composites. With this method, the formation of continuous conducting interconnected GNP‐CNT‐GNP or CNT‐GNP‐CNT network structure in the matrix polymer and strong π–π interaction between the electron rich phenyl rings and oxygen atom of PC chain, GNP, and MWCNT could be possible throughout the composites. POLYM. COMPOS., 37:2058–2069, 2016. © 2015 Society of Plastics Engineers     

Hybrid composites of ABS with carbonaceous fillers for electromagnetic shielding applications

This work evaluates the influence of two types of carbonaceous fillers, carbon black (CB) and carbon nanotubes (CNTs), on the electrical, electromagnetic, and rheological properties of composites based on poly(acrylonitrile‐co‐butadiene‐co‐styrene) (ABS) prepared by the melt mixing. Electrical conductivity, electromagnetic shielding efficiency (EMI SE) in the X‐band frequency range (8–12.4 GHz), and melt flow index (MFI) results showed that ABS/CNT composites exhibit higher electrical conductivity and EMI SE, but lower MFI when compared to ABS/CB composites. The electrical conductivity of the binary composites showed an increase of around 16 orders of magnitude, when compared to neat ABS, for both fillers. Binary composites with 5 and 15 wt % of filler showed an EMI SE of, respectively, ?44 and ?83 dB for ABS/CNT, and ?9 and ?34 dB for ABS/CB. MFI for binary composites with 5 wt % were 15.45 and 0.55 g/10 min for CB and CNT, respectively. Hybrid composites ABS/CNT.CB with 3 wt % total filler and fraction 50:50 and 75:25 showed good correlation between EMI SE and MFI. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46546.     

高导热苯乙烯丙烯酸树脂复合材料制备及导热性能

苯乙烯丙烯酸树脂为墨粉主要组分,其导热性能提升可显著提高墨粉导热性能,进而延长打印、复印机使用寿命。通过在苯乙烯丙烯酸树脂中添加碳纳米管、石墨烯高导热单一或复合填料,在苯乙烯丙烯酸树脂构建连通导热网络以提高其导热性能。当苯乙烯丙烯酸树脂中添加0.75wt%多壁碳纳米管时,其导热系数可提高至0.1644 W/(m?K),增幅为31.31%;添加1.0wt%羧基改性多壁碳纳米管时,苯乙烯丙烯酸树脂导热系数可提高至0.1751 W/(m?K),增幅为39.86%;在苯乙烯丙烯酸树脂添加多壁羧基改性碳纳米管和石墨烯混合填料时,苯乙烯丙烯酸树脂导热系数可提升至0.2093 W/(m?K),增幅达到67.17%。表明碳纳米管和石墨烯混合填料可在苯乙烯丙烯酸树脂中形成有效的导热网络,从而显著提高苯乙烯丙烯酸树脂导热性能。     

酚醛树脂/镀银碳纤维导热复合材料的制备与性能

采用化学镀的方法在碳纤维(CF)上镀一层银膜,然后采用搅拌混合的方法制备了酚醛树脂/镀银碳纤维(Ag-CF)导热复合材料,通过扫描电子显微镜(SEM)、X射线衍射仪(XRD)、X射线能量色散光谱仪(EDS)等方法对其结构和性能进行表征。结果表明,大量的银粒子均匀分布在CF表面;酚醛树脂/Ag-CF导热复合材料的导热系数、冲击强度和拉伸强度随着Ag-CF含量的增加而逐渐增加;Ag-CF的含量为7.0 %时,酚醛树脂/Ag-CF导热复合材料的综合性能最优,此时其导热系数为1.25 W/(m·K),冲击强度和弯曲强度分别为66.7 kJ/m2和139.2 MPa;残炭率为30 %时,添加量为7.0 %的复合材料对应温度为 500 ℃,高于纯酚醛树脂的 450 ℃。     

Floating catalyst chemical vapor infiltration of nanofilamentous carbon reinforced carbon/carbon composites – Integrative improvement on the mechanical and thermal properties

Nanofilamentous carbon (NFC) reinforced carbon/carbon composites were produced by floating catalyst chemical vapor infiltration with ferrocene content ranging 0–2.0?wt%. The NFCs and increased graphitization degree led to an improvement on the mechanical and thermal properties. An excellent combination of high strength and thermal conductivity (TC), and low coefficient of thermal expansion (CTE) was reached by adding 0.5–0.8?wt% catalyst. When the content exceeded 0.8wt%, the strength and TC were decreased by the limited NFC growth and matrix transited from rough laminar to isotropic pyrocarbon. After the treatment of 2500?°C, the strength and CTE decreased whereas the TC was increased. With the catalyst contents at 0.5–0.8?wt%, the flexural and shear strength retention ratios achieved a high value of 73.1–74.5 and 79.1–79.4%, respectively, and the in-plane and out-of-plane TCs exhibited maxima of 339.1 and 72.5?W/(m?K). Relatively low CTE was obtained at 2.0?wt% catalyst owing to the increased amount of cracks and pores.     

Effects of phenolic resin contents on microstructures and properties of c/sic-diamond composites

In this paper, C/SiC-diamond composites were obtained by chemical vapor infiltration (CVI) and reactive melt infiltration (RMI), and the effects of phenolic resin contents on the microstructures and properties of as-obtained C/SiC-diamond composites were studied. The results suggested a significant influence of phenolic resin contents on the pore structure of the composites before reactive melt infiltration (RMI), as well as phase composition and density of the matrix after RMI. The mechanical properties of composites were shown to correlate with the threshold effect of phenolic resin. Sample R5 prepared with high phenolic resin contents displayed significantly declined mechanical properties. On the other hand, adjustment of the phenolic resin content yielded samples with maximum room temperature thermal conductivity reaching 14.75 W/(m·K). The theoretical thermal conductivity of the composites calculated by the Hasselman-Johnson (H-J) theoretical model was estimated to 24.52 W/(m·K). Overall, the increase in phenolic resin content led to unreacted diamond-C regions and the formation of substantial porosity. These features reduced the thermal conductivity of the resulting C/SiC-diamond composites.     

Effects of two silane surface modifications with different functional groups on the thermal conductivity and mechanical properties of UV-cured composites with high ceramic filler loading

With rapid technological advancements, efficient thermal management is becoming increasingly important to sustain the stable operation of electronic devices. In this study, aluminum nitride (AlN) fillers with various acrylate monomers were subjected to two types of silane surface treatments to prepare composites with a high loading of AlN filler (65 wt%). The acrylates—isobornyl acrylate (IBOA), 1,4-butanediol diacrylate (BDDA), and trimethylolpropane triacrylate (TMPTA)—were mixed with bisphenol A ethoxylate dimethacrylate (Bis-EMA) as an oligomer, and phenylbis (2,4,6-trimethylbenzoyl)phosphine oxide (BAPO) as a photo-initiator in different proportions to obtain resin matrices. Pristine AlN and AlN functionalized with APTES and MPS were used as fillers. The effect of the acrylate functional group in silanes on the thermal and mechanical properties of the acrylate resin was explored. The thermal conductivities of the IBOA/AlN/APTES and IBOA/AlN/TMPTA composites with a high loading of the filler functionalized with APTES and MPS were 1.34 and 1.57 W/(m?K), respectively, 4.15 and 5.28 times higher than that of the composite with neat resin. The enhanced filler–matrix compatibility increased the tensile strength of the composites. The findings highlighted that silane functionalization of AlN can enhance the thermal conductivity and mechanical properties of the composite.     

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.     

PA6/CF/EG导电复合材料的制备与性能

采用熔融共混法制备了不同碳纤维/热膨胀石墨(CF/EG)比例的尼龙6/碳纤维/热膨胀石墨(PA6/CF/EG)导电复合材料并研究其性能。结果表明,CF的加入能显著提高复合材料的力学性能;而随着EG含量的提高,复合材料的导电性能和导热性能显著提高,但力学性能在一定程度上得到降低。当CF质量分数为20%时,复合材料具有最优的力学性能,当EG质量分数为20%时,复合材料体积电导率可显著提高至0.262 S/m,热导率可达1.3379W/(m·K)。     

Study on the structure and properties of conductive silicone rubber filled with nickel‐coated graphite

In this study, the conductive silicone rubber composites filled with nickel‐coated graphite (NCG) have been prepared, and their morphology structure, electrical conductivity, electromagnetic interference shielding efficiency (EMI SE), and mechanical properties have been investigated with reference to the NCG filler loading. The mechanical strength of NCG particle was poor that it can be easily ground into smaller particle during the mixing process if the shear force during mixing is large enough. The electrical conductivity of the composites existed an obvious threshold value with the variation of the loading amount of the conductive filler. EMI SE of the composites increases with the decrease of the volume electrical resistivity. The Payne effect can be used to characterize the intensity of the three‐dimensional conductive network structure in silicone rubber matrix, and the difference of storage modulus in the low and high shear strain has good linear correlation with the electrical conductivity. So, the electrical conductivity and EMI SE can be estimated by means of the difference of storage modulus obtained from rubber process analysis test. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal transport phenomena and limitations in heterogeneous polymer composites containing carbon nanotubes and inorganic nanoparticles

An Off-Lattice Monte Carlo model was developed to investigate effective thermal conductivities (K_eff) and thermal transport limitations of polymer composites containing carbon nanotubes (CNTs) and inorganic nanoparticles. The simulation results agree with experimental data for poly(ether ether ketone) (PEEK) with inclusions of CNTs and tungsten disulfide (WS₂) nanoparticles. The developed model can predict the thermal conductivities of multiphase composite systems more accurately than previous models by taking into account interfacial thermal resistance (R_bd) between the nanofillers and the polymer matrix, and the nanofiller orientation and morphology. The effects of (i) R_bd of CNT–PEEK and WS₂–PEEK (0.0232–115.8 × 10⁻⁸ m²K/W), (ii) CNT concentration (0.1–0.5 wt%), (iii) CNT morphology (aspect ratio of 50–450, and diameter of 2–8 nm), and (iv) CNT orientation (parallel, random and perpendicular to the heat flux) on K_eff of a multi-phase composite are quantified. The simulation results show that K_eff of multiphase composites increases when the CNT concentration increases, and when the R_bd of CNT–PEEK and WS₂–PEEK interfaces decrease. The thermal conductivity of composites with CNTs parallel to the heat flux can be enhanced ∼2.7 times relative to that of composites with randomly-dispersed CNTs. CNTs with larger aspect ratio and smaller diameter can significantly improve the thermal conductivity of a multiphase polymer composite.     

A review of vapor grown carbon nanofiber/polymer conductive composites

Vapor grown carbon nanofiber (VGCNF)/polymer conductive composites are elegant materials that exhibit superior electrical, electromagnetic interference (EMI) shielding effectiveness (SE) and thermal properties compared to conventional conductive polymer composites. This article reviews recent developments in VGCNF/polymer conductive composites. The article starts with a concise and general background about VGCNF production, applications, structure, dimension, and electrical, thermal and mechanical properties. Next composites of VGCNF/polymer are discussed. Composite electrical, EMI SE and thermal properties are elaborated in terms of nanofibers dispersion, distribution and aspect ratio. Special emphasis is paid to dispersion of nanofibers by melt mixing. Influence of other processing methods such as in-situ polymerization, spinning, and solution processing on final properties of VGCNF/polymer composite is also reviewed. We present properties of CNTs and CFs, which are competitive fillers to VGCNFs, and the most significant properties of their composites compared to those of VGCNF/polymer composites. At the conclusion of the article, we summarize the most significant achievements and address the future challenges and tasks in the area related to characterizing VGCNF aspect ratio and dispersion, determining the influence of processing methods and conditions on VGCNF/polymer composites and understanding the structure/property relationship in VGCNF/polymer composites.     

高热导率聚丙烯/石墨复合材料的制备与性能

为了提高聚丙烯(PP)的导热性能,扩大其使用范围,采用价格低廉的商用石墨对PP进行改性,利用转矩流变仪制备了PP/石墨导热复合材料。研究了粒径为2μm和20μm的石墨及其复配对复合材料热导率及力学性能的影响。结果表明,复合材料的热导率随着石墨用量的增加而显著增大,20μm石墨填充的复合材料热导率高于2μm石墨填充的复合材料;由于石墨的各向异性,层内热导率远高于层间热导率;将两种粒径的石墨复配,固定石墨总质量分数为40%,当2μm石墨与20μm石墨质量比为1︰5时,复合材料层间和层内热导率达到最大,分别为1.125 W/(m·K)和2.897 W/(m·K),比相同用量下单一2μm石墨填充PP分别提高了121%和61%,比单一20μm石墨填充PP分别提高了3.6%和20%。随石墨用量增加,单一粒径石墨填充的复合材料拉伸强度和弯曲强度呈现先减小后增大的趋势,随复配填料中20μm石墨用量增加,复配填料填充复合材料的力学性能呈下降趋势,但弯曲强度变化不大,拉伸强度也在10 MPa以上。     

形态稳定的Na2SO4·10H2O-Na2HPO4·12H2O共晶盐相变储能材料的制备及热性能提升

在复合相变材料中引入碳纳米纤维(CNFs)提高相变体系的导热系数,以实现相变材料与外界环境进行快速有效的热量交换。本文采用熔融共混法将Na₂SO₄·10H₂O和Na₂HPO₄·12H₂O制备成共晶盐相变材料,借助聚丙烯酸钠构筑三维聚合物网络封装相变材料,利用CNFs提升复合材料的导热系数。通过Raman、XPS等测试方法,研究了CNFs经高能球磨、湿化学氧化处理后,其表面含氧官能团的变化;借助Raman、DSC、Hot disk、TG等测试方法,分析了CNFs对复合材料化学相容性、相变行为、热稳定性、潜热容量、导热系数的影响。结果表明:CNFs经过功能化处理,氧、碳原子比增大至0.140,氧化效果显著;CNFs引入至复合相变材料中,体系内各组分之间存在良好的化学相容性;当CNFs的添加量达到3%(质量分数),复合材料的固、液态导热系数分别达到1.05 W/(m·K)、0.88 W/(m·K),相较于未添加CNFs的复合材料,固、液态导热性能分别提升了69.4%、60.0%;经过1 000次循环试验,复合材料的熔融焓和结晶焓相较循环前分别下降了56.2%、65.3%,相变体系仍然具备一定的储热能力,表明将相变材料嵌入三维网络结构是一种有效的封装策略。     

Thermoplastic polyvinyl alcohol/multiwalled carbon nanotube composites: Preparation,mechanical properties,thermal properties,and electromagnetic shielding effectiveness

This study uses the solution mixing method to combine plasticized polyvinyl alcohol (PVA) as a matrix, and multiwalled carbon nanotubes (MWCNTs) as reinforcement to form PVA/MWCNTs films. The films are then laminated and hot pressed to create PVA/MWCNTs composites. The control group of PVA/MWCNTs composites is made by incorporating the melt compounding method. Diverse properties of PVA/MWCNTs composites are then evaluated. For the experimental group, the incorporation of MWCNTs improves the glass transition temperature (T_g), crystallization temperature, T_c), and thermal stability of the composites. In addition, the test results indicate that composites containing 1.5 wt % of MWCNTs have the maximum tensile strength of 51.1 MPa, whereas composites containing 2 wt % MWCNTs have the optimal electrical conductivity of 2.4 S/cm, and electromagnetic shielding effectiveness (EMI SE) of ?31.41 dB. This study proves that the solution mixing method outperforms the melt compounding method in terms of mechanical properties, dispersion, melting and crystallization behaviors, thermal stability, and EMI SE. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43474.     

Effect of N–Ni coordination bond on the electrical and thermal conductivity of epoxy resin/nickel-coated graphite

The agglomeration of nickel-coated graphite (NCG) in epoxy resin (EP) composites leads to low electrical conductivity of EP composites, which limits their development in electronic devices and multilayer circuits. In order to improve the electrical and thermal conductivity of NCG/EP composites, ethylenediamine (EDA) was used to modify NCG and compared with pure NCG-filled EP composites. It was found that the conductive effect of modified composites with 20 wt% filler is better than that of unmodified composites with 40 wt% filler. The results of Fourier transform infrared spectroscopy and thermogravimetric analysis of EDA-modified NCG (ENCG) showed that a coordination adsorption reaction occurred between EDA and NCG, forming N–Ni coordination bonds. When the filling amount of ENCG was 40 wt%, the conductivity and thermal conductivity of the composite are improved most significantly. The volume resistivity was reduced from 2.636 to 0.109 Ω cm, a decrease of 95.85%, and the thermal conductivity was improved from 0.517 to 0.968 W/(m K), an increase of 87.23%, respectively. Meanwhile, ENCG has better dispersion in the EP matrix than NCG.