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     

The effect of fluorosilicone modifiers on the carbon nanotube networks in epoxy matrix

Structure and properties of polymer compositions based on carbon nanotubes (CNTs) filled epoxy matrix containing fluorosilicone copolymers as additives is discussed. Electrical conductivity and dielectric (microwave) permittivity of the composites can be varied by approximately one order of magnitude without changing the CNT concentration, by careful selection of the additive type and concentration. The mutual solubility of the modifiers and epoxy is a key factor determining both rheological properties of the uncured compositions and electrical properties of cured CNT‐nanocomposites. CNT‐nanocomposites modified with amino‐functional (i.e., epoxy crosslinkable) copolymers demonstrate improved electrical conductivity values at increased additive concentration, connected with the formation of specific segregated microstructure. Fluorosilicone additives added in a specific amount also allow for a decrease of the viscosity of uncured epoxy CNT‐nanocomposites, improving their processability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46539.     

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     

Electrical and mechanical properties of carbon nanotube‐epoxy nanocomposites

In this work, electrical conductivity and thermo‐mechanical properties have been measured for carbon nanotube reinforced epoxy matrix composites. These nanocomposites consisted of two types of nanofillers, single walled carbon nanotubes (SW‐CNT) and electrical grade carbon nanotubes (XD‐CNT). The influence of the type of nanotubes and their corresponding loading weight fraction on the microstructure and the resulting electrical and mechanical properties of the nanocomposites have been investigated. The electrical conductivity of the nanocomposites showed a significantly high, about seven orders of magnitude, improvement at very low loading weight fractions of nanotubes in both types of nanocomposites. The percolation threshold in nanocomposites with SW‐CNT fillers was found to be around 0.015 wt % and that with XD‐CNT fillers around 0.0225 wt %. Transmission optical microscopy of the nanocomposites revealed some differences in the microstructure of the two types of nanocomposites which can be related to the variation in the percolation thresholds of these nanocomposites. The mechanical properties (storage modulus and loss modulus) and the glass transition temperature have not been compromised with the addition of fillers compared with significant enhancement of electrical properties. The main significance of these results is that XD‐CNTs can be used as a cost effective nanofiller for electrical applications of epoxy based nanocomposites at a fraction of SW‐CNT cost. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Enhanced Thermal Conductivity of Epoxy Composites with MWCNTs/AlN Hybrid Filler

To further improve the thermal conductivity of epoxy resin, the multi-walled carbon nanotube/aluminum nitride (MWCNTs/AlN) hybrid filler was employed to prepare thermal conductivity MWCNTs/AlN/epoxy composite by casting process, and the silane coupling reagent of γ-glycidoxy propyl trimethoxy silane(KH-560) was also used to functionalize the surface of MWCNTs and/or AlN. Results revealed that, the thermal conductivity of epoxy resin was improved remarkably with the addition of MWCNTs/AlN hybrid filler, a higher thermal conductivity of 1.04 W/mK could be achieved with 29 wt% MWCNTs/AlN hybrid filler (4 wt% MWCNTs +25 wt% AlN), about 5 times higher than that of native epoxy resin. And the epoxy composite with 29 wt% MWCNTs/AlN hybrid filler possessed better thermal conductivity and mechanical properties than those of single 5 wt% MWCNTs or 40 wt% AlN. The thermal decomposition temperature of MWCNTs/AlN/epoxy composite was increased with the addition of MWCNTs/AlN hybrid filler. For given filler loading, surface treatment of MWCNTs and/or AlN by KH-560 exhibited a positive effect on the thermal conductivity of epoxy composite.     

Preparation and properties of aluminum nitride‐filled epoxy composites: Effect of filler characteristics and composite processing conditions

Polymer‐matrix composites based on brominated epoxy as the matrix and aluminum nitride (AlN) particle as the filler were prepared. Effects of AlN size and content as well as composite processing conditions on the preparation and properties of the composites had been investigated. At the same processing conditions, Young's modulus (E) and dielectric constant (D_k) of the composites increase, whereas coefficient of thermal expansion decreases when increasing AlN content or decreasing AlN size; tensile strength and elongation at break first increase then decrease with AlN content, and they reach maximum values at lower AlN content with decreasing AlN size; glass transition temperature (T_g) also exhibits a trend of first increase then decrease with AlN content, and it decreases with decreasing AlN size, especially at high AlN content; dissipation factor (D_f) generally decreases with AlN content except for the composites filled with 50 nm‐AlN, and it increases with decreasing AlN size. Comparing the composites prepared at different processing conditions, the properties of the composite are relatively poor at low vacuum conditions during removal of solvent and bubble. The scanning electron microscope and Fourier transform infrared analyses indicate that the properties of the composites are related to the aggregation of AlN filler and voids in the composites as well as the crosslink density of epoxy matrix. The preparation of the composites is also found to be affected by AlN size and content as well as vacuum conditions, indicating that increase of viscosity of system and/or the solvent evaporation during curing results in poor formability of the composites. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

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     

Electrical and thermal properties of polyethylene/silver nanoparticle composites

The concentration dependence of specific heat, electrical and thermal conductivities of nanocomposites based on high‐density polyethylene (HDPE) filled with silver nanoparticles have been investigated. The composites filled with high filler content show high electrical and thermal conductivities. The dielectric relaxation spectroscopy was used to investigate the electrical properties in the studied systems. The scaling law of electrical percolation was used for an exact estimation of the percolation threshold (P_c). A low electrical percolation threshold was found in the investigated composites. The rule of mixture was sufficient for the prediction of the specific heat dependence of HDPE–Ag nanocomposites as a function of the weight filler content. The basic models of the thermal conductivity have a tendency to underestimate the measured values for the low and high filler concentrations. POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers POLYM. COMPOS., 2013. © 2013 Society of Plastics Engineers     

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)。     

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     

Thermal,dielectric, and rheological properties of aluminum nitride/liquid crystalline copoly(ester amide) composite for the application of thermal interface materials

In this article, thermally conductive and relatively low dielectric constant polymer matrix composites of an aluminum nitride filler (AlN) and a novel liquid crystalline copoly(ester amide) (LCP) were prepared via a solution blending method in the presence of a phosphate containing dispersant. The viscosities, thermal conductivities, and dielectric properties of the prepared AlN/LCP composites were investigated as a function of AlN loading. Our experimental results demonstrated that the AIN/LCP composite with AlN concentration of 50 wt% had 2.5 times higher thermal conductivity than pure LCP (2.020 and 0.817 W/mK for composite with 50 wt% of AlN and pure LCP, respectively), but its dielectric constant remained at low level, i.e., < 9.0 at frequency of 900 Hz. In addition, viscosities of AlN/LCP pastes in the N‐methyl‐2‐pyrrolidinone solvent remained at acceptable levels with the high AlN loading of 50 wt%. The morphologies of the prepared composites were also investigated by scanning electron microscopy. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

New PTCR thermistors,switching current,and electromagnetic shielding effectiveness from nanosized vanadium sesquioxides ceramic reinforced epoxy resin nanocomposites

A new polymer nanocomposites of an epoxy resin matrix with randomly dispersed nano‐vanadium sesquioxides (V₂O₃) in various amounts were prepared. The structure of the nanocomposites were characterized by scanning and transmission electron microscopy (SEM and TEM), X‐ray diffraction, hardness, packing factor, extent of filler reinforcement, glass transition temperature, and sound velocity. The percolation threshold in the conductivity of the composites is lesser than 8 wt % and the dielectric constant can reach as high as 103. The resistivity—temperature curve of the composites shows a positive temperature coefficient (PTC) effect. The thermal stability of the composites was examined in terms of thermal gravimetry and differential scanning calorimetry (TG and DTA) and isothermal resistivity–time check. Because of the interfacial interaction among filler particles and the epoxy matrix, the nanocomposites exhibit higher thermal stability. The current–voltage–temperature curves behave as switching current. The temperature increases linearly with the applied voltage which makes this PTC nanocomposites very useful for temperature probe. Finally, electromagnetic interference shielding effectiveness (SE) values have been calculated and measured for the nanocomposites in the frequency range 1–12 GHz. It is found that the SE properties of the nanocomposite improve with increase in wt % of V₂O₃. A maximum SE of 42 dB for V20 sample at 12 GHz has been achieved. These nanocomposites are potentially useful in suppression of electromagnetic interference and reduction of radar signature. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Effect of organosilane coupling agents on microstructure and properties of nanosilica/epoxy composites

Three types of silane coupling agents, γ‐aminopropyltriethoxysilane, γ‐glycidoxypropyltrimethoxysilane, and γ‐methacryloxypropyltrimethoxysilane, were used as modifiers to modify the surface of the nanosilica, respectively, and the nanocomposites of the epoxy resin filled with nano‐sized silica modified by three silane coupling agents were prepared by physical blending. The properties of the modified silica nanoparticles were characterized by Fourier transform infrared spectrum and particle‐size analyzer. The microstructure, mechanical behavior, and heat resistant properties of the nanocomposites were investigated by transmission electron microscopy, scanning electron microscopy, thermo gravimetric analyses, differential thermal gravity, differential scanning calorimetry, and flexural tests. The results showed that these modifiers are combined to the surfaces of nanosilica by the covalent bonds, and they change the surface properties of nanosilica. The different structures of coupling agents have different effects on the dispersibility and stability of modified particles in the epoxy matrix. In comparison, the silica nanoparticles modified by γ‐glycidoxypropyltrimethoxysilane exhibit a good dispersivity. The nanocomposites with 4 wt% weight fraction nanosilica modified by γ‐glycidoxypropyltrimethoxysilane have higher thermal decomposing temperature and glass transition temperature than those of the other two composites with the same nanosilica contents, and they are raised by 43.8 and 8°C relative to the unmodified composites, respectively. The modified silica nanoparticles have good reinforcing and toughening effect on the epoxy matrix. The ultimate flexural strengths of the composites with 4 wt% nanoparticles modified by γ‐aminopropyltriethoxysilane, γ‐glycidoxypropyltrimethoxysilane, and γ‐methacryloxypropyltrimethoxysilane are increased by 10, 30, and 8% relative to the unmodified composites, respectively. The flexural fracture surfaces of modified composites present ductile fracture features. POLYM. COMPOS. 2012. © 2012 Society of Plastics Engineers     

AC conductivity of carbon fiber–polymer matrix composites at the percolation threshold

This paper reports results on experimental investigation of the conductivity behavior of carbon fiber filled polymer composites at the percolation threshold. Two types of carbon fiber‐epoxy matrix composites have been studied and comparison of the measured data has been made. These two types of composites differ in the surface modification of carbon fibers (in one case the surface of carbon fibers is covered with polymer beads using the microencapsulation technology, in the other their surface stayed unmodified). Experimental data reveal that surface modification of carbon fibers influences greatly the DC conductivity (percolation threshold moves to higher concentrations) but does not influence the AC electrical properties. From the frequency dependence of conductivity upon fiber concentration it becomes clear that it is not possible to predict the high frequency conductivity (electromagnetic interference shielding properties) based on the DC conductivity. Percolation behavior of conductivity as a function of conductive filler concentration is typical only for DC or low frequency AC conductivity. The percolation threshold gradually vanishes for high frequencies of electromagnetic field. The temperature dependence of electrical properties has also been studied. Composites with concentration near the percolation threshold show the switch‐off effect (at the specific temperature the DC conductivity drops by several orders of magnitude). This switch‐off effect does not occur for high frequency AC conductivity.     

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     

Influence of carbon‐based nanofillers on the electrical and dielectric properties of ethylene vinyl acetate nanocomposites

A comparative study of ethylene vinyl acetate nanocomposites based on expanded graphite, multiwalled carbon nanotubes, and carbon nanofibers has been carried out to investigate the effect of different carbon nanofillers on the electrical properties of the corresponding composites. The composites were prepared by ultrasonic dispersion of fillers in ethylene vinyl acetate solution, followed by casting and compression molding. The dependence of AC conductivity and dielectric constant on the frequency and filler concentration was investigated. Carbon nanofibers provided maximum conductivity as well as lowest percolation threshold (8.2 vol%) compared to expanded graphite and multiwalled carbon nanotubes filled composites. The improvement in both electrical conductivity and dielectric constant was attributed to the high filler aspect ratio and the formation of conducting networks. The relationship of dielectric constant with filler volume fraction for all the composite systems is estimated using a power law. The pressure sensing capability of the composites at respective percolation thresholds was also compared. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

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     

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.     

Effect of Al2O3 addition on thermo‐electrical properties of polymer composites: An experimental investigation

To develop a new class of composites with adequately high thermal conductivity and suitably controlled dielectric constant for electronic packages and printed circuit board applications, polymer composites are prepared with microsized Al₂O₃ particle as filler having an average particle size of 80–100 μm. Epoxy and polypropylene (PP) are chosen as matrix materials for this study. Fabrication of epoxy‐based composite is done by hand lay‐up technique and its counterpart PP‐based composite are fabricated by compression molding technique with filler content ranging from 2.5–25 vol%. Effects of filler loading on various thermal properties like effective thermal conductivity (k_eff), glass transition temperature (T_g), coefficient of thermal expansion (CTE) and electrical property like dielectric constant (ε_c) of composites are investigated experimentally. In addition, physical properties like density and void fraction of the composites along with there morphological features are also studied. The experimental findings obtained under controlled laboratory conditions are interpreted using appropriate theoretical models. Results show that with addition of 25 vol% of Al₂O₃, k_eff of epoxy and PP improve by 482% and 498% respectively, T_g of epoxy increases from 98°C to 116°C and that of PP increases from −14.9°C to 3.4°C. For maximum filler loading of 25 vol% the CTE decreases by 14.8% and 26.4% for epoxy and PP respectively whereas the dielectric constants of the composites get suitably controlled simultaneously. POLYM. COMPOS., 36:102–112, 2015. © 2014 Society of Plastics Engineers     

Preparation,morphology, and properties of silane‐modified MWCNT/epoxy composites

Both epoxy resin and acid‐modified multiwall carbon nanotube (MWCNT) were treated with 3‐isocyanatopropyltriethoxysilane (IPTES). Scanning electron microscopy (SEM) and transmission electronic microscope (TEM) images of the MWCNT/epoxy composites have been investigated. Tensile strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 41% comparing to the neat epoxy. Young's modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 52%. Flexural strength of cured silane‐modified MWCNT (1.0 wt %)/epoxy composites increased 145% comparing to neat epoxy. Flexural modulus of cured silane‐modified MWCNT (0.8 wt %)/epoxy composites increased 31%. Surface and volume electrical resistance of MWCNT/epoxy composites were decreased with IPTES‐MWCNT content by 2 orders and 6 orders of magnitude, respectively. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010