Filler Size Research Articles

Thermal and Adhesion Properties of Fluorosilicone Adhesives Following Incorporation of Magnesium Oxide and Boron Nitride of Different Sizes and Shapes.

Thermally conductive adhesives were prepared by incorporating magnesium oxide (MgO) and boron nitride (BN) into fluorosilicone resins. The effects of filler type, size, and shape on thermal conductivity and adhesion properties were analyzed. Higher thermal conductivity was achieved when larger fillers were used, but smaller ones were advantageous in terms of adhesion strength. Bimodal adhesives containing spherical MgOs with an average particle size of 120 μm and 90 μm exhibited the highest conductivity value of up to 1.82 W/mK. Filler shape was also important to improve the thermal conductivity as the filler type increased. Trimodal adhesives revealed high adhesion strength compared to unimodal and bimodal adhesives, which remained high after aging at 85 °C and 85% relative humidity for 168 h. It was found that the thermal and adhesion properties of fluorosilicone composites were strongly affected by the packing efficiency and interfacial resistance of the particles.

Progress on the polymer composite insulating materials with high thermal conductivity

<p indent="0mm">The continuing miniaturization and increasing power density of electrical and electronic equipment have created higher requirements for the heat dissipation capacity of packing and insulating materials. Long-term operation of electronic devices will cause local overheating of core components, which will significantly affect the reliability and service life of the components. Heat dissipation has even become a technical bottleneck in the development of electronic devices with high integration. Therefore, developing new composite materials which offer excellent thermal conductivity has attracted significant interest worldwide in recent years. To address these issues, researchers improve the thermal conductivity of polymer materials mainly through the following two aspects. One is to modify the polymer body so that the internal molecular and chain structure of the polymer has a high degree of crystallization or orientation, thereby improving its thermal conductivity, but this method is a cumbersome preparation process and is still in the laboratory research stage. Second, inorganic fillers with high thermal conductivity can be filled in the polymer preparation process to form a thermal conductivity channel, thus improving the thermal conductivity. The latter composite material has been widely used in electronic packaging, electric machine potting and other fields because of its low cost, simple processing and convenient industrial production. This paper reviews the research status and progress of the preparation and application of composites with high thermal conductivity in recent years. Firstly, the factors that affect the thermal conductivity of materials are mainly introduced from two aspects: (1) The crystallinity of polymer matrix, the interaction between molecular chains and the micro-scale ordered structure; (2) the particle size, doping amount and geometry of thermal conductivity filler. Researchers have found that the key to obtaining composites with high thermal conductivity is to increase the ordered structure of the polymer or make the thermal conductivity packing form the maximum density thermal conductivity path consistent with the heat transfer direction in the polymer system. In view of the above key factors, we summarize five preparation methods that significantly improve the thermal conductivity of composites: Functionalized packing surface treatment, random blending, electrostatic spinning, field control and three-dimensional skeleton construction. Among them, constructing the 3D skeleton is considered as the most promising method at present. A large number of papers reported the use of casting technology, 3D printing technology and other methods to prepare three-dimensional thermal conductivity networks. In the casting technology, the 3D thermal skeleton is firstly formed by the ice template method or salt template method, and then the polymer matrix such as epoxy resin and PDMS is poured into the 3D skeleton to obtain the composite material with high thermal conductivity. This method fundamentally improves the thermal conductivity of composites. Finally, in view of the current situation of polymer insulating materials with high thermal conductivity in industry applications, we provide an outlook on the future directions for the development of composite materials. It is hoped that material properties can be optimized from the microscopic point of view in the future to obtain polymer composites with higher thermal conductivity with less filler and lower cost.

Highly anisotropic thermal conductivity and electrical insulation of nanofibrillated cellulose/Al2O3@rGO composite films: effect of the particle size

Nanofibrillated cellulose (NFC) film has received tremendous attention due to its excellent electrical insulation, which shows great application prospects in the field of electronic devices. However, the low efficient heat dissipation of NFC film largely limits its use in advanced applications. In this work, the reduced graphene oxide hybrid fillers loaded alumina (Al2O3) particles with different sizes were synthesized by different drying methods, and then they were mixed with NFC to prepare a series of NFC-based composite films. The effect of Al2O3 particle sizes on the thermal conductivity of NFC-based composite films was studied. The results showed that the surface areas of l-Al2O3 particles were smaller than that of s-Al2O3 particles, resulting in the smaller interface thermal resistance and superior thermal conductivity of the film containing l-Al2O3 particles. The NFC-based composite films showed great potential for applications in thermal management by adjusting the particle size of fillers.

Effect of eggshell fillers on the tensile and flexural properties of glass fiber reinforced polymer composites

The natural bio-filler collected from waste such as chicken eggshells have been widely used as a value-added product in many applications. Recently, the utilization of eggshell bio-filler has also been found in polymer composites. This paper reports the effect of eggshell filler loading percentage and size on the tensile and flexural properties of glass fiber-reinforced polymer (GFRP) composites. Epoxy composite panels with four layers of plain-woven fabric of 800 gsm fabricated with 0 wt%, 10 wt%, 25 wt%, and 40 wt% eggshell powder (ESP) fillers using the wet hand lay-up technique. The chicken eggshells were dried, ground, and sieved into 53 μm and 150 μm filler size. The tensile and flexural tests were conducted according to ASTM D3039 and ASTM D7264. The tensile and flexural properties (both stress and modulus) were reduced with increasing filler loading from 10 wt% to 40 wt% for both filler sizes. The optimal filler loading has been achieved in 10 wt% of eggshell fillers for both filler sizes of 53 μm and 150 μm.

Epoxy Molding Compound Filler Clogging Simulation During Integrated Circuit Encapsulation Process

As IC components become denser and smaller in a package, more problems emerge. In the mold filling process, because epoxy molding compound (EMC) contains approximately 80 wt.&#x0025; silica fillers, the fillers may clog at the gate of gap if the gap height between the component and the substrate is too small. This clogging will cause a popcorn effect due to the high resin content in the gap. In order to determine the EMC filling process in the mold cavity and the relation between the gap height and the filler size, we simulate the EMC filling process and the EMC filler concentration distribution in the mold cavity using mold flow analysis software and then use computational fluid dynamics-discrete element method (CFD-DEM) coupling method to simulate the EMC filler motion to determine the relationship between gap height and filler size and the factors that affect filler clogging. Based on the mold flow analysis results, the filler concentration was higher at the gate of gap than in other regions, and the filler concentration at the gate of gap for the 30-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> gap-height model was higher than that for the 50-<inline-formula> <tex-math notation="LaTeX">$\mu \text{m}$ </tex-math></inline-formula> gap-height model. Based on the DEM-CFD coupling results, particles with a single diameter larger than one-half of the gap height caused particle clogging the gate of gap, and particles with a mean particle size larger than one-third of the gap height caused particle clogging the gate of gap.

Preclinical testing of an anal bulking agent coated with a zwitterionic polymer in a fecal incontinence rat model.

Fecal incontinence is a disabling condition in which the passage of fecal material cannot be controlled. Although the condition is not life-threatening, it can seriously reduce the quality of life of a patient by isolating them from others. Though various surgical treatments are available for moderate to severe symptoms, a bulking agent is a minimally invasive technique that has attracted attention because of its safety and simple treatment process. However, the biocompatibility of bulking agent materials remains a central issue, with their durability questioned because immune responses and/or the circulatory system may remove the bulking agent in vivo. This study investigated a bulking agent composed of polydimethylsiloxane and hyaluronic acid as a microfiller and carrier gel, respectively. To improve the injectability of the bulking agent, the filler size was tuned using a suspension-based fabrication technique. To evade immune responses, the filler surface was treated with a zwitterionic polymer that simultaneously functionalized and stabilized the material interfaces. The resulting bulking agent exhibited good injectability and biocompatibility in vitro, with 58% lower protein adsorption and no cytotoxicity, leading to an improved bulking effect in a preclinical rat model compared with a bulking agent without surface treatment. These results illustrate the promising potential of bulking agents as a therapy for fecal incontinence with reduced foreign body reactions and long-lasting efficacy.

A new study of dynamic mechanical analysis and the microstructure of polyurethane foams filled.

Polyurethane foams have good shock-absorbing properties. This article discusses the study of the physical, dynamic analysis, and microstructure of filled polyurethane foams (PUR). We used mineral fillings nanoparticles of titanium dioxide (TiO2) and calcium carbonate (C1) to support and strengthen the foam cell structure to develop shock absorption and thermal resistance properties. Dynamic mechanical analysis (DMA) and compression tests compared the mechanic characterization results with different modelling approaches. For studies of physicochemical properties, we used differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). We deduced the flame retardancy mechanism. It appears that a detailed description of the characteristics of viscosity and yield stress must take into consideration the filler's size in comparison to the cell wall's size. The effect of size distribution on the foam's microstructure was given by scanning electron microscopy (SEM). Half-open spherical cells were shown to be reduced in size with filling. The filler diffusion in polyurethane foams was used to model the composite foam. We observed that crystalline filler particles were uniformly distributed in the matrix, indicating that the total size is related to the density and is a crucial metric for the level of reinforcement.

Epoxy-based composites with enhanced thermal properties through collective effect of different particle size fillers

Taking advantages of excellent adhesion and insulating properties, polymer-based thermal interface materials have been widely used in electrical and electronic industry. However, applications was limited due to the existence of high interfacial resistance and poor mechanical properties resulted from poor dispersion and weak interfacial adhesion of thermal conductive fillers in the polymer matrix. Herein, different sizes of aluminum oxide microparticle was used as thermal conductive fillers to fabricate a series of high thermal conductive epoxy composites, and the effect of fillers loading ratio on the properties of thermal conductive, mechanical, thermal stability was further analyzed. The optimum composite exhibits a high thermal conductivity (1.91 ± 0.02 W·m−1·K−1) at a loading ratio of 1: 2 (20-μm: 70-μm, mass ratio), which is equivalent to a thermal conductivity enhancement of 950% in comparison with pure epoxy resin. The outstanding properties of the as-prepared composite is mainly attributed to the effective conductive network formed by different size fillers that the smaller particles act as a bridge to connect the larger one. This work has proved by Agari model that combining different sizes Al2O3 as fillers is a workable way to obtain composite with high thermal conductivity and it is expected to provide a reliable route for the preparation of thermally conductive composites with different particle sizes.

Amino functionalized boron nitride and enhanced thermal conductivity of epoxy composites via combining mixed sizes of fillers

With the emergence of 5G communication and the rapid development of the microelectronics industry, the heat dissipation of high power circuits has become quite an important issue. Along these lines, the thermal conductivity distribution of the electronic packaging materials, which plays a key role in the protecting circuits, requires urgent improvement. In this study, amino-functional boron nitride nanosheets (BNNS) were prepared by employing ball milling boron nitride with urea (aqueous solution) as agents. Then, the epoxy composites filled with large size pristine boron nitride (pBN) and small size functional boron nitride were fabricated by using the wet ball-milling (wBN) technique. The acquired results indicate that the thermal conductivity property of the pBN/wBN/epoxy composites with pBN/wBN ratio of 2.5/7.5 can reach the value of 0.386 W/mK, which is 96% higher than that of pure epoxy. Meanwhile, the measured value is superior from both the pBN/epoxy and wBN/epoxy composites with the same filling amount. This effect can be attributed to the efficient construction of the fillers network and thermal conduction path. Within the epoxy matrix, wBN can fill the pores between pBN and form a denser filler network. In addition, the amino-functional groups grafted with wBN result in their enhanced dispersion within the epoxy matrix that leads to a more stronger interfacial effect. Our approach provides useful insights in understanding the incorporation mechanisms of fillers in polymers, and thereby enhancing their potential applications.

FLUENT Simulation Design and Optimization of Biological Aerated Filter

In this paper, a small biological aerated filter for experimental use was designed, and a method was explored to optimize the nitrogen removal efficiency by using FLUENT software to simulate the particle size of the filler, the amount of the filler, the initial concentration of ammonia nitrogen, dissolved oxygen and other operating parameters. Through the simulation experiment, the optimal design parameters of the particle size of filler, the amount of filler, the initial concentration of ammonia nitrogen and the dissolved oxygen of the biological aerated filter are 4mm, 60%, 15% and 1.5%, respectively, when the removal efficiency of ammonia nitrogen exceeds 30% reported in the literature. It provides a reference for the experimental research and practical application of biological aerated filter (BAF) denitrification.

Effect of size of the filler on the electrical conductivity of magnesium ion conducting polymer electrolyte

The electrical characteristic studies on new polymer electrolyte system ((PMMA)x- ((Mg(CF3SO3)2)1-x)y - (TiO2)1-y have been explored in association with structural characterization, where in amorphous polymer PMMA is mixed with magnesium triflate salt and the filler TiO2.The constituent phases of the synthesized samples by solution casting technique were investigated by powder X-ray Diffraction analysis (XRD) and spectral analysis by Fourier Transform Infra-Red spectroscopy (FTIR).Surface morphology of the prepared samples were carried out by Scanning Electron Microscopy (SEM).The electrical conductivity studies were undertaken with the help of AC impedance analysis to the four different compositions of the synthesized System I with the addition of titanium dioxide of particle size 133 nm as filler and found to exhibit electrical conductivity of the order of 10-6 to 10-7 S cm−1 at room temperature (303 K). AC impedance analysis on four different compositions of the System II with the addition of titanium dioxide of particle size 76 nm as nano filler exhibits electrical conductivity values of the order of 10-6 Scm−1 at room temperature (303 K) with one magnitude increase in ionic conductivity. The particular composition with filler size of 76 nm (((PMMA)70 – (Mg(CF3SO3)2)30)90 - (TiO2)10 shows an ionic conductivity value of 1.78 × 10-6 Scm−1 at room temperature (303 K) which could be considered as best conducting composition.

Expansion of Takayanagi model by interphase characteristics and filler size to approximate the tensile modulus of halloysite-nanotube-filled system

Existing models are unacceptable for the modulus of nanocomposites, because they disregard the interphase section. In the present work, the interphase features (depth and modulus) and halloysite nanotube (HNT) size (radius and length) are added to Takayanagi model to obtain an advanced model for the modulus of HNT-based system. The accuracy of advanced model is examined by the experimented values of modulus for numerous examples and by the clarifying of the impacts of all factors on the modulus of system. The tested facts of modulus for various types of examples certify the approximations of the advanced model. The absence of interphase section improves the nanocomposite's modulus by 8.2%, but the modulus of samples raises by 16.2% at the interphase depth of 20 nm. The interphase modulus of 10 GPa increases the nanocomposite's modulus by 10.5%, while the modulus of system promotes by 12.6% at interphase modulus of 60 GPa. Additionally, HNT radius of 20 nm enhances the modulus of system by 14.5%, but HNT radius of 60 nm negligibly grows the modulus of samples by 9.7%. Accordingly, the deepness and modulus of interphase section straightly control the modulus of system, while HNT radius plays an opposite role in the stiffening.

A protocol to further improve the thermal conductivity of silicone-matrix thermal interface material with nano-fillers

Silicone oil is used as matrix material and five nano-materials after surface treatment are employed as additives for preparing high performance silicone based thermal paste. The effects of filler weight fraction, morphologies and sizes on the thermal conductivity of polymer composites are studied. Experiment results show that the composite filled with ball-shaped aluminum (Al) particles exhibits high thermal conductivity (1.55 W/(m K)) at 80 wt.% loading, which is 7.6 times greater than pure silicone oil. Rod-shaped filler is more easily to form heat conductive pathways than ball-, platelet- and other irregular-shaped fillers. The effective synergistic enhancement in phonon transport in composites is achieved and a further 63% improvement in the thermal conductivity is realized by adding 75 wt.% ball-shaped Al particles and 10 wt.% rod-shaped zinc oxide (ZnO). Finally, the obtained data are compared with the value calculated by the theoretical thermal conductivity prediction models.

Investigation on the preparation, properties, and microstructure of high thermal conductive cementing material in 3500m-deep geothermal well

The development and utilization of geothermal energy can effectively alleviate many environmental issues caused by fossil fuel combustion and the global shortage of fossil energy. Cementing materials have an important influence on the parameters of geothermal wells. Through the orthogonal test, SEM, XRD, MIP, and other methods, the effects of the type, particle size, and content of thermal conductive filler on the performance of cementing materials were studied. High thermal conductive cementing material (HTC) for geothermal wells was prepared. The basic physical properties, micromorphology, phase composition, and pore structure of HTC were tested, and the thermally conductive mechanism of HTC was summarized. The results show that graphite has the best effect on improving the thermal conductivity of cement. With the larger particle size and amount of graphite, the thermal conductivity of cement is greater, but the compressive strength is smaller. The formula of HTC has been obtained as follows: 0.44 W/C ratio, 7 wt% graphite, 4 wt% iron powder, 2 wt% quartz sand, in which the particle sizes of graphite are 150 μm and 100 μm which mix in the ratio of 3:1. The thermal conductivity of HTC is 2.003 W/(m·K), which is 69.5% higher than that of high-sulfate-resistant G-grade oil well cement (HGC), and the 48 h compressive strength is 23.38 MPa, which is 3.07% lower than that of HGC. Compared with HGC, the overall structure of HTC is slightly loose, but the degree of hydration is higher. A large number of hydration products such as Ca(OH)2, C-S-H, and AFt are formed, but the pore structure of HTC is slightly poor. The harmful porosity of HTC is 6.46%, which is 3.20% higher than that of HGC. The thermally conductive mechanism of HTC conforms to the theory of heat conduction path, and it is at the beginning of the third stage. The research results can provide theoretical guidance for the preparation and performance research of similar materials, promoting the efficient development and utilization of deep geothermal energy.

Effect of Surface Polishing on Nano-Hardness and Elastic Modulus of Different Resin Composites after Immersion in Alcoholic Medium

There has been a great tendency toward using resin composite in dentistry and exploring nano-hardness, elastic modulus, and effect of polishing on its mechanical properties after its artificial ageing. This study aimed to evaluate the effect of surface polishing of four different resin composites on their nano-hardness and elastic modulus. This effect was tested right after light curing of composite resin and after its artificial ageing (immersion in alcoholic medium). Nanoindentation test preparations, surface roughness, surface hardness, and scanning electron microscope were conducted across the four different resin composites: Clearfil AP-X (APX), Estelite Sigma Quick (ESQ), Beautifil II (BE2), and FiltekTM Supreme Ultra Universal restorative (FSU). We found that difference in fillers load and particle size are amongst the factors influencing hardness and modulus of elasticity. The APX is the highest in term of hardness due to fillers load and size while the ESQ is the lowest because all fillers in nano size and distributed homogenously. The significance of surface polishing of the studied resin composite restorations was highlighted. Future research may focus on exploring survival rate of polished and non-polished composite surfaces with emphasis on measuring degree of conversion and impacts of polished and non-polished surfaces on the individuals’ oral health quality of life.

Effect of graphene size on the mechanical and damping properties of polyether amine modified r-GO and ZnO multi-nanoparticles filled epoxy

To prepare structural damping epoxy nanocomposites, three kinds of organic–inorganic hybrids containing r-GO@ZnO nanoparticles with different graphene sizes and polyether amine were synthesized. The mechanical and damping properties of the epoxy nanocomposites containing 2 wt% of the hybrids were investigated. It is found that the filler size has a significant effect on the mechanical and damping properties of nanocomposites. The nanocomposite containing the smallest size hybrid had the highest bending strength and impact strength, which improved by 3.9 % and 59.7 % respectively. The nanocomposite containing the biggest size hybrid had the highest bending modulus, which improved by 28.8 %. The medium size hybrid had little effect on the mechanical properties of nanocomposite, it is more effective in improving the damping properties, and the loss factor of nanocomposite is increased by at least 38.4% at the glass stage.

Influence of the Size of the Fiber Filler of Corn Stalks in the Polylactide Matrix Composite on the Mechanical and Thermomechanical Properties.

This paper presents results of a study on the effect of filler size in the form of 15 wt% corn stalk (CS) fibers on the mechanical and thermomechanical properties of polylactide (PLA) matrix composites. In the test, polylactidic acid (PLA) is filled with four types of length of corn stalk fibers with a diameter of 1 mm, 1.6 mm, 2 mm and 4 mm. The composites were composed by single screw extrusion and then samples were prepared by injection molding. The mechanical properties of the composites were determined by static tensile test, static bending test and Charpy impact test while the thermo-mechanical properties were determined by dynamic mechanical thermal analysis (DMTA). The composite structures were also observed using X-ray microcomputed tomography and scanning electron microscopy. In the PLA/CS composites, as the filler fiber diameter increased, the degradation of mechanical properties relative to the matrix was observed including tensile strength (decrease 22.9–51.1%), bending strength (decrease 18.9–36.6%) and impact energy absorption (decrease 58.8–69.8%). On the basis of 3D images of the composite structures for the filler particles larger than 2 mm a weak dispersion with the filler was observed, which is reflected in a significant deterioration of the mechanical and thermomechanical properties of the composite. The best mechanical and thermomechanical properties were found in the composite with filler fiber of 1 mm diameter. Processing resulted in a more than 6-fold decrease in filler fiber length from 719 ± 190 µm, 893 ± 291 µm, 1073 ± 219 µm, and 1698 ± 636 µm for CS1, CS1.6, CS2, and CS4 fractions, respectively, to 104 ± 43 µm, 123 ± 60 µm, 173 ± 60 µm, and 227 ± 89 µm. The fabricated green composites with 1 to 2 mm corn stalk fiber filler are an alternative to traditional plastic based materials in some applications.

Nanocomposite of Fullerenes and Natural Rubbers: MARTINI Force Field Molecular Dynamics Simulations.

The mechanical properties of natural rubber (NR) composites depend on many factors, including the filler loading, filler size, filler dispersion, and filler-rubber interfacial interactions. Thus, NR composites with nano-sized fillers have attracted a great deal of attention for improving properties such as stiffness, chemical resistance, and high wear resistance. Here, a coarse-grained (CG) model based on the MARTINI force field version 2.1 has been developed and deployed for simulations of cis-1,4-polyisoprene (cis-PI). The model shows qualitative and quantitative agreement with the experiments and atomistic simulations. Interestingly, only a 0.5% difference with respect to the experimental result of the glass transition temperature (Tg) of the cis-PI in the melts was observed. In addition, the mechanical and thermodynamical properties of the cis-PI-fullerene(C60) composites were investigated. Coarse-grained molecular dynamics (MD) simulations of cis-PI-C60 composites with varying fullerene concentrations (0–32 parts per hundred of rubber; phr) were performed over 200 microseconds. The structural, mechanical, and thermal properties of the composites were determined. The density, bulk modulus, thermal expansion, heat capacity, and Tg of the NR composites were found to increase with increasing C60 concentration. The presence of C60 resulted in a slight increasing of the end-to-end distance and radius of the gyration of the cis-PI chains. The contribution of C60 and cis-PI interfacial interactions led to an enhancement of the bulk moduli of the composites. This model should be helpful in the investigations and design of effective fillers of NR-C60 composites for improving their properties.

Highly Permeable Mixed Matrix Hollow Fiber Membrane as a Latent Route for Hydrogen Purification from Hydrocarbons/Carbon Dioxide.

This work reported on the fabrication and investigation of a mixed matrix hollow fiber membrane (MMHFM) by incorporating commercially available alumina particles into a polyetherimide (PEI) polymer matrix. These MMHFMs were prepared by the dry-wet spinning technique. Accordingly, optimizing the spinning parameters, including the air gap distance and flow rate ratio, is key to determining the gas separation performance. However, there are few studies regarding the effect of the filler dimensions. Consequently, three sizes of alumina particles, 20 nm, 30 nm, and 1000 nm, were respectively added into the PEI phase to examine the influence of filler size on gas permeation property. Moreover, the permeation properties of lower hydrocarbons (i.e., ethane and propane) were also measured to evaluate potential for emerging applications. The results indicated the as-synthesized membrane exhibited a remarkable hydrogen permeance of 1065.24 GPU, and relatively high separation factors of 4.53, 5.77, and 5.39 for H2/CO2, H2/C2H6, and H2/C3H8, respectively. This resulted from good compatibility between the larger fillers and the PEI polymer, as well as a reduction in the finger-like voids. Overall, the MMHFM in this work was deemed to be a promising candidate to separate hydrogen from gas streams, based on the comparison of the separation performance against other reported studies.

Enhanced thermal conductivity of epoxy composites by constructing thermal conduction networks via adding hybrid alumina filler

AbstractHigh thermal conductivity of polymer composites could be achieved through constructing 3D continuous thermally conductive networks into polymer composites. Herein, we demonstrate a simple, effective method to optimize the segregated alumina networks by using ternary mixture of alumina particles with different diameter ratios (5.8 μm + 2.6 μm + 0.5 μm) at the fixed total content of 60 wt% via conventional melt blending method. The thermal properties of epoxy composites were investigated as a function of the weight fraction and particle size of alumina particles. The thermal conductivity (TC) values of composites with coarse fillers (13.2 μm) are in agreement with Agari model at high filler loading (57 ~ 67 wt%). And the value of C2 was ~0.949 (close to 1), indicating that the formation of heat conduction paths in the composites. The addition of 60 wt% smaller fillers (2.6 μm) facilitates a higher interaction degree between the polymer/fillers, consequently, leads to a higher Tg of 147.8°C. A high TC of 1.109 W m−1 K−1 is achieved as the ratio of alumina filler with different particle sizes is 7/2/1, corresponding to a TC enhancement of 23%–32% compared to the composites with a single particle size filler. A suitable proportion of hybrid fillers is crucial for constructing three‐dimension continuous network, in which nano‐particles filled between the micro‐particles could increase the particle‐to‐particle connectivity.