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     

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.     

A Novel Polymeric Coating with High Thermal Conductivity

A novel polymeric coating with high thermal conductivity was prepared using a hydroxyl-terminated polydimethylsiloxane-modified epoxy resin and hybrid aluminum nitride (AlN) particles with various sizes. It was found that the coating exhibited a maximum thermal conductivity of 1.78 W/m K at 50 wt% filler content and a preferable mass ratio. This was a result of the synergistic effect of hybrid fillers giving rise to a better heat conduction capability as opposed to a coating without fillers. Furthermore, thermogravimetric analysis revealed that the coating exhibited an excellent high temperature resistance owing to the modified matrix and interaction between filler and matrix; and a dielectric study demonstrated that the dielectric constant, volume resistivity and dielectric strength of the coating at 50 wt% filler concentration were 5.6, 8.2 × 10¹³ Ω·cm and 12 kV/mm, respectively. In addition, the mechanical properties declined obviously with filler content.     

Mechanical,thermal and electrical properties of multi‐walled carbon nanotube/aluminium nitride/polyetherimide nanocomposites

A series of polyimide‐based nanocomposites containing polyimide‐grafted multi‐walled carbon nanotubes (PI‐g MWCNTs) and silane‐modified ceramic (aluminium nitride (AlN)) were prepared. The mechanical, thermal and electrical properties of hybrid PI‐g MWCNT/AlN/polyetherimide nanocomposites were investigated. After polyimide grafting modification, the PI‐g MWCNTs showed good dispersion and wettability in the polyetherimide matrix and imparted excellent mechanical, electrical and thermal properties. The utilization of the hybrid filler was found to be effective in increasing the thermal conductivity of the composites due to the enhanced connectivity due to the high‐aspect‐ratio MWCNT filler. The use of spherical AlN filler and PI‐g MWCNT filler resulted in composite materials with enhanced thermal conductivity and low coefficient of thermal expansion. Results indicated that the hybrid PI‐g MWCNT and AlN fillers incorporated into the polyetherimide matrix enhanced significantly the thermal stability, thermal conductivity and mechanical properties of the matrix. Copyright © 2012 Society of Chemical Industry     

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.     

New composites with high thermal conductivity and low dielectric constant for microelectronic packaging

Three composites based on cyanate (CE) resin, aluminum nitride (AlN), surface‐treated aluminum nitride [AlN(KH560)], and silicon dioxide (SiO₂) for microelectronic packaging, coded as AlN/CE, AlN(KH560)‐SiO₂(KH560)/CE, and AlN‐SiO₂/CE composite, respectively, were developed for the first time. The thermal conductivity and dielectric constant of all composites were investigated in detail. Results show that properties of fillers in composites have great influence on the thermal conductivity and dielectric constant of composites. Surface treatment of fillers is beneficial to increase the thermal conductivity or reduce dielectric constant of the composites. Comparing with binary composite, when the filler content is high, ternary composites possess lower thermal conductivity and dielectric constant. The reasons leading to these outcomes are discussed intensively. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

高导热低黏度环氧树脂灌封胶

以E-51型环氧树脂为基体,Al2O3为导热填料,CYH-277为稀释剂制备高导热低黏度环氧树脂灌封胶。优化了硅烷偶联剂KH-560、稀释剂CYH-277的用量;分别采用NDJ-7型旋转式黏度计和Hot Disk型热常数分析仪测试其黏度和导热系数。结果表明:硅烷偶联剂KH-560用量为1.25%(wt)时效果最优;随CYH-277用量的增加灌封胶黏度、耐热性能均逐渐下降,最佳用量为25%(wt);随Al2O3用量增加,灌封胶的黏度、导热系数均增大;用量相同时,填充20μm Al2O3的树脂体系相比于填充6μm Al2O3树脂体系黏度小、导热系数大,复配两种粒径Al2O3对应树脂体系的导热性最好;复配Al2O3用量为86%(wt)时,导热系数达到2.23W/(m·K),此时灌封胶的黏度为30100mPa·s,仍保持较好的加工流动性。     

High thermal conductivity epoxy molding compound filled with a combustion synthesized AlN powder

A combustion synthesized AlN powder was studied for its feasibility as a filler for epoxy molding compound (EMC) and effects of various experimental parameters on the thermal conductivity and moisture resistance of the EMC were investigated. The AlN powder was coated with silane both to increase the moisture resistance of the EMC and to enhance the bonding between the filler AlN and the matrix resin. The thermal conductivity could be significantly increased by using AlN powders with large particle sizes and this was considered to be due to a reduction in interface area between the AlN particles and the matrix resin. A thermal conductivity of 14 W/mK was obtained when the EMC was fabricated by a process involving no use of a solvent and a AlN powder with a particle size of 35.3 μm and a filler content of 67 vol % were used. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4734–4740, 2006     

Thermal conductivity of a graphene oxide–carbon nanotube hybrid/epoxy composite

Thermally conductive graphene oxide (GO)–multi-wall carbon nanotube (MWCNT)/epoxy composite materials were fabricated by epoxy wetting. The polar functionality on the GO surface allowed the permeation of the epoxy resin due to a secondary interaction between them, which allowed the fabrication of a composite containing a high concentration of this hybrid filler. The thermal transport properties of the composites were maximized at 50 wt.% of filler due to fixed pore volume fraction in filtrated GO cake. When the total amount of filler was fixed 50 wt.% while changing the amount of MWCNTs, a maximum thermal conductivity was obtained with the addition of about 0.36 wt.% of MWCNTs in the filler. Measured thermal conductivity was higher than the predicted value based on the by Maxwell–Garnett (M–G) approximation and decreased for MWCNT concentrations above 0.4%. The increased thermal conductivity was due to the formation of 3-D heat conduction paths by the addition of MWCNTs. Too high a MWCNT concentration led to increased phonon scattering, which in turn led to decreased thermal conductivity. The measured storage modulus was higher than that of the solvent mixed composite because of the insufficient interface between the large amount of filler and the epoxy.     

BN/环氧树脂导热灌封胶的制备与性能

采用硅烷偶联剂KH-560对氮化硼(BN)进行表面处理,用于制备BN/环氧树脂导热灌封胶。结果表明,随着BN用量的增加,环氧导热灌封胶的剪切强度下降,导热性能则增加,表面改性有助于提高环氧灌封胶的剪切强度和导热性能。CTBN的加入可有效提高剪切强度。当改性BN和CTBN质量分数均为15%时,BN/环氧灌封胶具有较理想的剪切强度、热性能和导热性能。     

石墨烯改性对环氧树脂/碳纤维复丝拉伸性能的影响

采用直接分散法和上浆剂法分别制备了环氧树脂/碳纤维复丝,通过红外光谱、分光光度法等分析方法对处理的石墨烯的表面官能团及表面形貌进行表征,借助扫描电子显微镜对碳纤维表面进行微观形貌观察,研究了石墨烯改性对环氧树脂/碳纤维复丝界面性能的影响。结果表明:石墨烯表面成功地接枝了硅烷偶联剂KH-560;接枝硅烷偶联剂KH-560的石墨烯的环氧树脂/碳纤维复丝的拉伸性能优于未经改性的石墨烯的复丝;上浆法制得的环氧树脂/碳纤维复丝的拉伸性能优于分散法制得的复丝的拉伸性能;上浆剂法制备的石墨烯改性的环氧树脂/碳纤维复丝的断裂强力比未经过改性的未上浆的复丝的提高了48.6%,拉伸强度提高了30.4%,断裂伸长率提高了90.9%。     

Dynamic cure kinetics of epoxy/TiO2/MWCNT hybrid nanocomposites

The effect of multi-walled carbon nanotubes (MWCNTs) on cure kinetic parameters of the epoxy/amine/TiO₂ (1 wt%) resin system was studied dynamically at four heating rates using DTA. The presence of MWCNT in various amounts (0.1, 0.2, 0.4 and 0.6 wt%) neither retarded nor accelerated the cure reaction of the epoxy/amine/TiO₂ system in a considerable extent. Addition of MWCNTs increased the extent of cure of the corresponding nanocomposites, especially at higher contents up to 0.4 wt% MWCNT filled composite. However, increasing the MWCNT content to 0.6 wt% adversely affected the extent of cure due to nanoparticle agglomeration. The fracture surface morphology of the nanocomposites revealed that the cracks deviated on reaching the MWCNTs, while propagating in the polymer matrix. Fractional extent of conversion (α) was calculated using genetic algorithm. Flynn–Wall–Ozawa and Kissinger methods were used to analyze the kinetic parameters. The presence of MWCNTs did not affect the autocatalytic cure mechanism of epoxy/amine/TiO₂ resin system and also did not cause any considerable barrier effect on the curing process. Activation energy data fitted well in the cubic polynomial regression equations and the changes of E _a with respect to α proved the autocatalytic cure mechanism, being followed by all the MWCNT-containing epoxy-based hybrid nanocomposites.     

氮化铝/氧化石墨烯对环氧树脂胶黏剂导热性能的影响

使用硅烷偶联剂KH-560对氮化铝进行了表面改性,并以其为导热填料,环氧树脂为基体,制备了氮化铝/环氧树脂导热胶黏剂。采用FTIR、SEM、TG、热常数分析仪对导热胶黏剂进行了表征。结果表明:改性后硅烷偶联剂分子成功接枝在氮化铝表面。改性后,氮化铝与环氧树脂的界面粘结力增强,热稳定性和导热性均得到明显改善。当氮化铝质量为导热胶黏剂质量的70%时,改性氮化铝/环氧树脂热胶黏剂的导热系数为2.24W/(m·K),而未改性氮化铝/环氧树脂的导热系数仅为1.73W/(m·K)。为进一步提高其导热性能,制备了改性氮化铝/氧化石墨烯/环氧树脂导热胶黏剂,当改性氮化铝和氧化石墨烯的质量分数分别为50%和3%时,导热胶黏剂导热系数为3.05 W/(m·K)。     

Thermal conductive composites based on silver‐plating graphite nanosheet and epoxy polymer

Silver plating graphite nanosheet (Ag‐NanoG) prepared by electroless plating method with expanded graphite as starting material is an effective approach to increase thermal conductivity of the filler. Herein, a novel thermal conductive composite was prepared by using Ag‐NanoG as thermal conductive filler and epoxy resin as the polymer matrix. The microstructures of NanoG and Ag‐NanoG were characterized by means of scanning electron microscopy, X‐ray powder diffraction and then the thermal conductivity, impact strength, and thermal stability of the composite were investigated. The results showed that the Ag‐NanoG was successfully obtained and it can be homogeneously dispersed in the epoxy resin. The thermal conductivity of composite increased from 0.328 to 1.847 W/m K with 4 wt% Ag‐NanoG filler content. Moreover, the composite exhibited excellent thermal stability and mechanical property. POLYM. COMPOS., 38:2822–2828, 2017. © 2015 Society of Plastics Engineers     

Preparation and thermal effects of polyarylene ether nitrile aluminium nitride composites

Particulate‐filled polyarylene ether nitrile (PEN) composites were prepared using methyltriethoxy‐silane‐treated aluminium nitride (AlN) as the filler for thermal modification. The effects of AlN fraction, particle size and surface treatment on the thermal performance of PEN were investigated. The thermal conductivities of the composites increased when the AlN filler concentration was increased, as well as with decrement of the filler size. The thermal conductivity value of the composites increased up to 0.779 W m^?1 K^?1 when the AlN weight loading was 60 wt%. The trend of the thermal conductivities of the composites can be more efficiently predicted by theoretical models than empirical models. The composites exhibited stable performances of thermal decomposition and thermal expansion when AlN filler faction in the composites increased. © 2013 Society of Chemical Industry     

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.     

Mechanical,thermal, and dielectric properties of aluminum nitride/glass fiber/epoxy resin composites

The treated hybrid fillers of aluminum nitride/glass fibers (AlN/GF) were performed to prepare the AlN/GF/epoxy composites by casting method. Results showed that the flexural and impact strength of the composites were increased firstly, but decreased with the excessive addition of AlN. The mechanical properties were optimal with 5 wt% treated AlN. The thermal conductivities of the composites were improved with the increasing content of AlN, and the thermal conductive coefficient λ was 1.412 W/mK with 70 wt% treated AlN, about seven times higher than that of pure epoxy resin. The dielectric constant and dielectric loss of the composites were increased with the increasing content of AlN. For a given AlN/GF hybrid fillers loading, the surface treatment of AlN/GF hybrid fillers exhibited a positive effect on the mechanical properties and thermal conductivities of the composites. POLYM. COMPOS., 35:381–385, 2014. © 2013 Society of Plastics Engineers     

环氧树脂／碳化硅晶须导热复合材料的制备研究

用共混复合-浇注成型法制备环氧树脂／碳化硅晶须（EP／SiCw）导热复合材料,研究了导热填料种类、形状、用量和表面处理对复合材料的导热性能、力学性能和热性能的影响。结果表明,SiCw较SiCp更易改善材料的导热性能,热导率随SiCw用量的增加而增大,当SiCw体积分数为42．1％时,复合材料热导率为0．9611W／（m·K）;力学性能随SiCw用量的增加先增加后降低。表面处理有利于提高复合材料的导热性能和力学性能。SiCw的加入使环氧树脂的耐热性提高、Tg降低。     

The Preparation and Cure Kinetics Researches of Thermal Conductivity Epoxy/AlN Composites

The aluminum nitride (AlN) was employed to prepare epoxy/AlN composites by blending-casting moulding method, two different coupling agents were used to functionalize the surface of AlN. The thermal conductivity and mechanical properties of the composites were investigated. And the cure kinetics of the EP/AlN composites was studied by means of isothermal DSC. Results revealed that the thermal conductivity of EP improved remarkably with the addition of AlN, a higher thermal conductivity of 1.05 W/mK can be achieved with 42 vol% AlN, about 5 times higher than that of native epoxy resin. And the flexural and impact strength of the EP/AlN composites were optimal with 3.3 vol% AlN. The curing process of the EP/AlN composites contained autocatalytic mechanism, the whole process was according with the Kamal model. The presence of AlN did not change the cure reaction mechanism, and had little effecting on the activation energy, but decreased the rate constants k_l and k₂.     

Noncovalent functionalization of carbon nanotubes using branched random copolymer for improvement of thermal conductivity and mechanical properties of epoxy thermosets

A branched random copolymer, poly[(hydroxyethyl acrylate)‐r‐(N‐vinylcarbazole)] (BPHNV), was synthesized through a facile one‐pot free radical polymerization with hydroxyethyl acrylate and N‐vinylcarbazole monomers, using 4‐vinylmethylmercaptan as the chain transfer agent. BPHNV was employed to noncovalently modify multiwall carbon nanotubes (MWCNTs) by π–π interaction. The as‐modified MWCNTs were then incorporated into epoxy resin to improve the thermal conductivity and mechanical properties of epoxy thermosets. The results suggest that, due to both the conjugation structure and the epoxy‐philic component, BPHNV could form a polymer layer on the wall of MWCNTs and inhibit entanglement, helping the uniform dispersion of MWCNTs in epoxy matrix. Owing to the unprecedented thermal conductivity of MWCNTs and the enhancement in the interfacial interaction between fillers and matrix, the thermal conductivity of epoxy/MWCNTs/BPHNV composites increases by 78% at extremely low filler loadings, while the electrical resistivity is still maintained on account of the insulating polymer layer. Meanwhile, the mechanical properties and glass transition temperature (T_g) of the thermosets are elevated effectively, with no significant decrease occurring to the modulus. The addition of as little as 0.1 wt% of MWCNTs decorated with 1.0 wt% of BPHNV to an epoxy matrix affords a great increase of 130% in impact strength for the epoxy thermosets, as well as an increase of over 13 °C in T_g. © 2018 Society of Chemical Industry