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Abstract

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.

Keywords

Different particle size thermal conductivity agari model

Introduction

Owing to the fast development and miniaturization of modern electronic devices, efficient heat dissipation is urgently desired.^1–4 Rapid accumulation of heat will damage electronic equipment inevitably and seriously threaten the lifetime.^4–7 Epoxy resins have been extensively used as general matrix on account of their wide acceptability of various fillers, which endows it the potential of being a new kind of thermal interface materials (TIMs).^4,8–12 However, their scope of application extremely restricted by the inherent fragility and low thermal conductivity of pure epoxy. Therefore, incorporating fillers becomes greatly important since mechanical properties and thermal properties of the composites would be enhanced.^8,13–18

The incorporation of fillers endows epoxy resins with improved mechanical property and thermal conductivity, a variety of fillers with outstanding thermal conductivity and mechanical properties have so far been incorporated with epoxy resins to obtain epoxy-based composites with superior properties. The common strategy for improving the thermal conductive of epoxy resins is to directly couple epoxy-based matrix with highly thermal conductive fillers, such as SiO₂,^19–22 SiC,^23–25 AlN,^26–29 BN.^16,26,30,31 In addition to the type of fillers, filler size, shape and content also affect the performance of the composite material.^32–36 Zhao et al.³⁷ prepared an epoxy-based material using the BN sheets and microspheres, where the BN microspheres play a role of bridge to connect the adjacent flakes. The composites with a filler loading of 30 wt % exhibited a thermal conductivity of 1.148 W·m⁻¹·K⁻¹. Moradi et al.³⁸ report the thermal conductivity of hybrid epoxy-BN composites with different sizes and type of BN, samples has a thermal conductivity greater than 10 W·m⁻¹·K⁻¹ when it cured under pressures of 175 kPa at 44.7 vol %.

Spherical Al₂O₃ microparticle is one kind of inorganic fillers which has the features of outstanding electrical insulation properties, high thermal conductivity (33–36 W·m⁻¹·K⁻¹) and excellent stability.^39–42 An efficient thermal conductive pathway formed by Al₂O₃ microparticle which contact each other would contribute to heat dissipation and further improve the thermal conductivity of the composites.^36,43–45 However, single size Al₂O₃ ceramics have high brittleness and limited fracture toughness,⁴⁶ which could lead to poor final performance of the whole structure.⁴⁷ To avoid such a situation, different particle sizes or completely different fillers were used to prepare composite materials. Li et al.³² used micro Al₂O₃ and AlN to fabricate composites. When the fillers amount were 60 wt%, and the mass ratio of 48-μm spherical Al₂O₃ and 14-μm AlN was 1:2, there were2was evident contact between two particles and several conductive paths were formed, which led to a relative high thermal conductivity of 2.44 W·m⁻¹·k⁻¹. Zhou et al.³⁷ investigated the effect of particle size of Al₂O₃ on the properties of silicon rubber composites. A conclusion was drew that efficient networks were built when the mass ratio of Al₂O₃ was 2:5:1:1 (25-μm: 5-μm: 0.5-μm: 50-nm) and the total volume fraction was 64%. Furthermore, the thermal conductivity of the obtained composites is 1.45 W·m⁻¹·K⁻¹, which is 7 times that of the original silicon rubber.

In this work, epoxy-based composites incorporated with different sizes of spherical Al₂O₃ microparticle were fabricated. A series of fillers with diameter of 20-μm, 30-μm, 50-μm and 70-μm were chosen in the case of the total mass fraction is 75 wt%. Additionally, by changing the amount of different size Al₂O₃ under a certain range, we analyzed the effect of combining Al₂O₃ with different sizes on mechanical and thermal properties of the composites. Moreover, the calculation and comparison of the Agari models proves the reliability of our experimental results, which is expected to be applied to the next generation of electronic packaging.

Experimental section

Materials

Al₂O₃ sphere (average diameters were 20-μm, 30-μm, 50-μm and 70-μm) were purchased from Qinhuangdao ENO High-Tech Material Development Co., Ltd (Qing Huangdao, China). Epoxy resin used in this work was bisphenol A diglycidyl ether purchased from Jiangyin Thousands Chemicals Co., Ltd (Jiangyin, China). Curing agent and curing accelerator were dicyandiamide (DCD) and 1, 1-dimethyl-3-phenylurea (Fenuron), respectively, provided by Ellsworth Trading (Shenzhen) Co., Ltd (Shenzhen, China). Release agent dimethicone was purchased from Dongguan Kangjin New Material Technology Co., Ltd (Dongguan, China). Poly tetra fluoroethylene (PTFE) moulds were purchased from Xing Anda hardware and plastic Products Co., Ltd (Shenzhen, China).

Preparation of composites incorporated with complex sizes of Al₂O₃

As shown in Figure 1, all the composites were fabricated through the method of simple blending. Firstly, Al₂O₃ spheres were pretreated with ethanol and then dried in an oven. PTFE moulds were smeared with release agent and preheated at 90°C. Subsequently, Al₂O₃ sphere, epoxy resin, curing agent and curing accelerator were weighed, typically 32.7 g, 10 g, 0.75 g and 0.15 g, respectively. Then, Al₂O₃ sphere and epoxy resin were mixed under ultrasonic bath. After adding curing agent and accelerator, the compound was blended evenly by a laboratory homogeneous dispersing machine (Shanghai Angni instrument Co., Ltd, AD 500S-H). Afterwards, the mixture was poured into the preheated mould, degassing in a vacuum oven at 60°C and 1 MPa for 6 h. Finally, the mixture was cured at 90°C for 3 h, 105°C for 2 h and 120°C for 1 h. The obtained composites were taken out of the moulds, washed and waiting for further tests. Composites combined with single-sized Al₂O₃ were fabricated through same processes used for comparison. Composites were labeled as Sample n (n = 1, 2, 3…16) and S n (n = 20, 30, 50, 70), details were listed in Table 1.

Figure 1.

Schematic illustration for the preparation process of PE/Al₂O₃ composite.

Table 1.

Ratio of different sizes of spherical Al₂O₃ in the composite (total filler amount was 75 wt%).

Sample	20-μm (wt%)	30-μm (wt%)	50-μm (wt%)	70-μm (wt%)	Total amount (wt%)
1	0	0	50	25	75
2	0	0	25	50	75
3	0	25	0	50	75
4	0	25	50	0	75
5	0	25	25	25	75
6	0	50	0	25	75
7	0	50	25	0	75
8	25	0	0	50	75
9	25	0	25	25	75
10	25	0	50	0	75
11	25	25	0	25	75
12	25	25	25	0	75
13	50	0	0	25	75
14	50	0	25	0	75
15	50	25	0	0	75
16	25	50	0	0	75
PE	0	0	0	0	0
S20	75	0	0	0	75
S30	0	75	0	0	75
S50	0	0	75	0	75
S70	0	0	0	75	75

Measurement

Morphology

The morphology of composite’s cross-section was observed by field emission scanning electron microscope (Nova NanoSEM 230, Czech Republic). Samples were brittlely broken by liquid nitrogen and were coated with gold to increase resolution.

Tensile test

The tensile test was conducted on an electronic universal testing machine (CMT4104, America) according to ISO 527-2-2012. The stretching speed was 5 mm·min⁻¹, and the tensile strength was calculated by the following formula: $σ = \frac{F}{A}$ (1)where, σ is the tensile strength, MPa, F is the maximum load on samples, N and A is the stress area, mm².

Young’s modulus can be obtained from stress-strain curve by calculating slope of the curve at strain range 0–0.5% .³⁸ Sample image was shown in Supplemntal Figure S5 (a).

Impact strength

The impact strength was conducted according to ISO 179-1:2010 by using a Charpy impact tester (JC-5, China). Tests were carried out by using a 15 J hammer with 3.8 m·s⁻¹ impact velocity at room temperature, and the impact strength was calculated by the following formula:

S = \frac{A}{b \times d}

(2)

where, S is the impact strength of the sample, KJ·m⁻², A is the impact energy consumed by the sample, J, b is the sample width, mm and d is the remaining thickness of the sample, mm. Sample image was shown in Supplemntal Figure S5 (b).

Dynamic mechanical analysis

Storage modulus and loss factor (tanα) were measured on a dynamic mechanical analyzer (DMA1, Mettler-Toledo, Swizerland). The program was under tensile mode, temperature ranged from 30°C to 210°C at a heating rate of 5°C·min⁻¹ and frequency of 1 Hz. The sample had a size of 16×4×1 mm³, the abrasive papers with 200-grit was used first and followed by 600-grit one to smooth the surface of samples before measurement and make it easy to test.

Thermal analysis

Thermostability of the sample was tested by using a thermogravimetric analyzer (TGA 8000, Perkin-Elmer, America). All the samples were tested under argon atmosphere with temperature rise of 20°C·min⁻¹ from 25°C to 700°C.

Thermal conductivity and thermal diffusion coefficient of the sample were measured utilizing a thermal constant analyzer (Hot disk, Sweden). Two specimens shall be clamped on to both sides of the hot-disc probe and make sure that there are no defects on the surface. The probe is a slice with continuous double helix structure. To guarantee the accuracy of the results, the samples were made 20×20×10 mm³ and were tested for five times to acquire average values. Samples image was shown in Supplemntal Figure S7 (c).

Results and discussion

Morphology

Cross-sectional images of four samples were given in Figure 2 to present inner morphology of the composites and dispersion condition of Al₂O₃. Samples present different section morphology under the circumstances of different filler loading ratios. It is shown that Al₂O₃ distribute within the epoxy matrix without forming obvious agglomeration, which reduces the possibility of defects formation. In Figure 2(a), much void can be seen due to the fact that there are only big size fillers in the composite. As shown in Figures 2(b)-(d), the gap between fillers reduced with the increased amount of small size fillers. Supplemntal Figure S1 schematically illustrates the difference between single-sized filler and different-sized fillers. It is worth noting that there are more gaps in single-sized system than in different-sized system, thus heat conduction is easier in different-sized system due to the interconnected Al₂O₃ network. Red arrows in Figure 2 show a certain path along which the heat could be conducted, and it should be pointed out that workable paths would form only when the ratio of big and small size fillers is appropriate. Besides, heat could transfer in multiple directions under the circumstance of high filler loading (75 wt%) and well-dispersed.

Figure 2.

SEM images of samples: n = 2 (a), n = 8 (b), n = 9 (c), n = 14 (d).

Tensile strength

Tensile strength was used to evaluate the resistance ability of the composites to external tensile force. Stress-strain curves were displayed in Supplemntal Figure S2. We can observe from Figure 3 that the tensile strength of sample 8 is 37.90 ± 2.49 MPa when the mass ratio of 20-μm and 70-μm Al₂O₃ is 1:2, which shows a decrease compared with pure epoxy polymer (53.25 ± 3.05 MPa). According to some researches,⁴⁸ the addition of fillers in epoxy matrix may led to a decrease in the tensile strength, owing to insufficient stress transfer occurring at interfaces between filler and matrix.

Figure 3.

Tensile strength and Young’s modulus of sample n (a) n = 1, 2, 3…8 (b) n = 9, 10, 11…16 (c) PE, S20, S30, S50 and S70.

Young’s modulus reflected the ability of the composite to resist outside force and remain original shape. In Figure 3, all the samples show improved Young’s modulus compared with pure epoxy composite (1.00 ± 0.01 MPa). Composite incorporated with 20-μm and 70-μm Al₂O₃ (sample 8) has a Young’s modulus of 2.15 ± 0.08 MPa. Besides, different-sized Al₂O₃ endows composite with better Young’s modulus. This is owe to the fact that different-sized Al₂O₃ tends to disperse well within polymer matrix, enabling the composite to store energy sufficiently and maintain its original shape.⁴⁸

Impact strength

Impact tests were carried out to estimate composites’ resistance ability to external impact force. Figure 4 clearly depicted the effect of incorporation of Al₂O₃ on impact strength. The impact strength of pure epoxy composite is 1.57 ± 0.16 KJ·m⁻², and it is evident that the filling of Al₂O₃ enormously increased composites’ impact strength because of the toughening improvement of Al₂O₃.⁴⁹ Besides, when the mass ratio of 20-μm and 70-μm Al₂O₃ is 1:2 (sample 8), impact strength of the composite reaches 8.04 ± 1.47 KJ·m⁻², while composites filled with single size Al₂O₃ show a maximum of 4.33 ± 0.43 KJ·m⁻². All the composites filled with different-sized Al₂O₃ showed excellent impact strength compared with those are not, indicating better toughening improvement of different-sized Al₂O₃. The difference may be attributed to the fact that single-sized Al₂O₃ tend to agglomerate and thus forming more defects within the composite. On the contrary, different-sized Al₂O₃ are more likely to uniformly distribute within the epoxy matrix, hence inhibiting crack propagation when small cracks have formed.

Figure 4.

Impact strength of sample n (a) n = 1, 2, 3…16 (b) PE, S20, S30, S50 and S70.

Dynamic mechanical analysis

Dynamic mechanical analysis was adopted to assess the interaction between fillers and epoxy matrix by investigating stiffness and damping characteristics of the composites. Figure 5 shows the storage modulus of the composites. Compared with pure epoxy composite (Figure 3(c)), samples which incorporated with Al₂O₃ hugely increase the storage modulus. It was confirmed that the filling of Al₂O₃ endows composites with better ability to transfer stress from matrix to fillers since the storage modulus reflect the inner interactions between fillers and epoxy matrix.⁵⁰ Moreover, composites combined with different-sized Al₂O₃ have relatively higher storage modulus since different size fillers can act as pinning to transfer stress and enhance the mechanical properties of the material and restricted mobility of polymer chains, which reduces the problems of agglomeration, bubbles, stress concentration points and defects caused by high content of single particle size filler.

Figure 5.

Storage modulus of sample n (a) n = 1–4 (b) n=5–8 (c) n = 9–12 (d) n = 13–16.

Figure 6 demonstrates the loss factor (tan α) of the composites. Loss factor is also known as damping factor, which represents elastic or viscous properties of the composites and reflects the energy dissipation within the composites. The incorporation of single-sized Al₂O₃ obviously lowers the peak of tan α to 0.5 or less compared with pure epoxy composite had a loss factor whose peak value is about 0.55 (Figure 4(b)). However, composites added with different-sized Al₂O₃ almost have no change contrast to pure epoxy composite. The materials which compound with Al₂O₃ have an increased energy storage. Moreover, doping effect contribute to the energy dissipation. In single–sized system, the tan α decreased while the opposite occurred in different-sized system due to the enhancement of energy storage .⁵¹

Figure 6.

Tan α of sample n (a) n = 1–4 (b) n = 5–8 (c) n = 9–12 (d) n = 13–16.

Glass transition temperature (T_g) can be obtained from tan α-temperature curves. T_g is a very important thermophysical parameter which represents the highest application temperature for epoxy composites. T_g of all the samples are listed in Table 2 and Supplemntal Table S1. It is worth noting that T_g is related to molecular chains movement within the composite, the incorporation of Al₂O₃ made it harder for molecular chains to move freely when the temperature rise. Therefore, the composite tends to stay in glass state in a wider temperature range instead of changing into rubber state.⁵⁰ When the mass ratio of 20-μm and 70-μm Al₂O₃ is 1:2 (sample 8), T_g of the composite reaches to 174.9°C, 40°C increased than that of pure epoxy composite. Moreover, composites filled with single-sized Al₂O₃ exhibit relatively lower increase in T_g, from 3°C to 10°C probably. On the contrary, composites incorporated with different-sized Al₂O₃ display more evident increase, from at least 20°C to over 40°C, suggesting that molecular chain movement in different-sized system was difficult.

Table 2.

Glass transition temperature of sample n (n = 1, 2, 3…16).

Sample	T_g/°C
1	169.9
2	172.2
3	161.1
4	169.3
5	170.9
6	154.5
7	168.5
8	174.9
9	157.0
10	163.4
11	152.6
12	159.0
13	161.9
14	161.2
15	161.3
16	161.8

Thermal analysis

Thermal stability of different-sized samples is shown in Figure 7. It is evident that all the samples exhibit two main degradation stages during the overall process. First stage occurred at the temperature between 350°C and 450°C, corresponding to degradation of the cured epoxy network. Second stage took place from 450°C to around 650°C, which is due to the decomposition of the remains from the cured epoxy network.⁵² Figure 7(e) shows that in the temperature range of 350°C to 450°C, the decomposition rate of pure epoxy groups is between 80% and 90%. As what we have told above, the fillers with different size could act as pinning to restrict the movement of polymer chains.

Figure 7.

Thermostability of sample n (a) n = 1–4 (b) n = 5–8 (c) n = 9–12 (d) n = 13–16 (e) PE, S20, S30, S50 and S70.

Figure 8 is given to display thermal conductivity and thermal diffusion coefficient of the samples. Pure epoxy composite shows a thermal diffusion coefficient of 0.137 ± 0.003 mm²·s⁻¹, while after adding with single-sized Al₂O₃, thermal diffusion coefficient slightly increased. Besides, the incorporation of different-sized Al₂O₃ endows composites with better thermal diffusion coefficient, which may be concluded to better distribution of Al₂O₃ within the composite.³²

Figure 8.

Thermal conductivity and thermal diffusion coefficient of sample n (a) n = 1, 2, 3…8 (b) n = 9, 10, 11…16 (c) PE, S20, S30, S50 and S70.

While thermal conductivity of pure epoxy composite is 0.204 ± 0.008 W·m⁻¹·K⁻¹, it is worth pointing that the filling of Al₂O₃ tremendously improves composite’s thermal conductivity. Besides, when the mass ratio of 20 μm and 70 μm Al₂O₃ is 1:2 (Sample 8), the composite shows the highest thermal conductivity of 1.91 ± 0.02 W·m⁻¹·K⁻¹, totally 950% of that of pure epoxy composite. Such an increase could be attributed to the interconnected Al₂O₃ which supported the conformation of thermal path way. The Al₂O₃-Al₂O₃ thermal interface resistance is much smaller than the Al₂O₃-epoxy thermal interface resistance, thus making it easier to conduct heat in the composite. Temperature-time curves are given in Supplemntal Figure S6 to further exhibit thermal conduction ability of the samples. As shown in Supplemntal Figure S6 (b-f), after the filling of Al₂O_3, the surface temperature of samples displays much faster increase than that of pure epoxy composite. Moreover, samples with different-sized Al₂O₃ present slightly faster increase in temperature rising speed compared with that of samples with single-sized Al₂O₃, which is consistent with their thermal conductivity and proves that samples with different-sized Al₂O₃ have excellent ability of heat transfer.

Calculation by optimized Agari model

Agari et al. put forward with a new model to calculate thermal conductivity value based on extensive researches.⁴⁴ The model can calculate system’s thermal conductivity value in which two or more kinds of fillers exist. Its mathematical form is as follow:

\log λ = V \cdot (X_{2} \cdot C_{2} \cdot \log λ_{2} + X_{3} \cdot C_{3} \cdot \log λ_{3} + \dots) + (1 - V) \cdot \log (C_{1} \cdot λ_{1})

(3)

where, λ is the thermal conductivity value of the system, V is the total volume of different kind of fillers, X₂, X₃, X₄

\dots

are the ratio of each kind of fillers in the mixture of different fillers, C₂, C₃, C₄

\dots

are factors that are easy to form conductive chains, ranging from 0 to 1, λ₁, λ₂, λ₃

\dots

are the thermal conductivity value of each kind of fillers and C₁ is the factor that particles affect on crystallinity and crystal size of the polymer.

In this work, different size of Al₂O₃ are considered as different kinds of fillers. Density, weight, and thermal conductivity of fillers and polymer are constantly. According to Agari’s researches, C₁ is less than 1. The formula is changed into the following form:

\log \frac{λ - 0.2}{φ} = 0.53 \log 35 \cdot (X_{2} \cdot C_{2} + X_{3} \cdot C_{3} + \dots) + 0.47 \log 0.18

(4)

where, λ is the thermal conductivity value of the system, X₂, X₃, X₄

\dots

are the weight ratio of each kind of fillers in the system, C₂, C₃, C₄

\dots

are factors that are easy to form conductive chains, which can be obtained from

\frac{π}{30}, \frac{π}{20}, \frac{π}{12}

and

\frac{7 π}{60}

and φ is the correction factor whose value is 2.

Figure 9 displays comparison between actual thermal conductivity values and calculated. It can be clearly seen the tiny differences based on the comparison, the actual value deviates only slightly from the theoretical value, suggesting that the new model can excellently predict actual value. But it has to be noticed that both Agari model and our new model do not consider the interaction between particles and particles and particle morphology, which may have a significant effect on the thermal conductivity of the composites and cause errors.

Figure 9.

Comparison between actual value and theoretical value of sample n (n = 1, 2, 3…16).

Conclusion

In summary, we have fabricated a series of epoxy-based materials with efficient conductive network which were achieved by filling different sizes of Al₂O₃ sphere microparticles. The optimum as-prepared composite has a high thermal conductivity of 1.91 ± 0.02 W·m⁻¹·K⁻¹ at 75 wt% Al₂O₃ (20 μm: 70 μm = 1:2 wt%) loading, which is close to the theoretical value calculated by optimized Agari model and superior to pure epoxy resin. In addition, it has outstanding mechanical properties, tensile strength, Young’s modulus and impact strength of 37.90 ± 2.49 MPa, 2.15 ± 0.07 MPa and 8.04 ± 1.48 KJ·m⁻², respectively. Besides, the high glass transition temperature (174.9°C) of the composite suggesting a strong thermal stability and wider ranges of application. Considering all merits, the as-prepared Al₂O₃/epoxy composites have great potential and vast application prospects in the field of electronic packaging, integrated circuits and other relative fields.

Supplemental Material

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

Supplemental Material for Epoxy-based composites with enhanced thermal properties through collective effect of different particle size fillers by Xiaoyang Zeng, Zhengguo Zhang, Yaoqi Pan, Yongle Zhang and Linxi Hou in Polymers and Polymer Composites

Footnotes

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

ORCID iD

Linxi Hou

Supplemental Material

Supplemental material for this article is available online.

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Supplementary Material

Please find the following supplemental material available below.

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Sample	20-μm (wt%)	30-μm (wt%)	50-μm (wt%)	70-μm (wt%)	Total amount (wt%)
1	0	0	50	25	75
2	0	0	25	50	75
3	0	25	0	50	75
4	0	25	50	0	75
5	0	25	25	25	75
6	0	50	0	25	75
7	0	50	25	0	75
8	25	0	0	50	75
9	25	0	25	25	75
10	25	0	50	0	75
11	25	25	0	25	75
12	25	25	25	0	75
13	50	0	0	25	75
14	50	0	25	0	75
15	50	25	0	0	75
16	25	50	0	0	75
PE	0	0	0	0	0
S20	75	0	0	0	75
S30	0	75	0	0	75
S50	0	0	75	0	75
S70	0	0	0	75	75

Sample	20-μm (wt%)	30-μm (wt%)	50-μm (wt%)	70-μm (wt%)	Total amount (wt%)
1	0	0	50	25	75
2	0	0	25	50	75
3	0	25	0	50	75
4	0	25	50	0	75
5	0	25	25	25	75
6	0	50	0	25	75
7	0	50	25	0	75
8	25	0	0	50	75
9	25	0	25	25	75
10	25	0	50	0	75
11	25	25	0	25	75
12	25	25	25	0	75
13	50	0	0	25	75
14	50	0	25	0	75
15	50	25	0	0	75
16	25	50	0	0	75
PE	0	0	0	0	0
S20	75	0	0	0	75
S30	0	75	0	0	75
S50	0	0	75	0	75
S70	0	0	0	75	75

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

Abstract

Keywords

Introduction

Experimental section

Materials

Preparation of composites incorporated with complex sizes of Al2O3

Measurement

Morphology

Tensile test

Impact strength

Dynamic mechanical analysis

Thermal analysis

Results and discussion

Morphology

Tensile strength

Impact strength

Dynamic mechanical analysis

Thermal analysis

Calculation by optimized Agari model

Conclusion

Supplemental Material

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

Footnotes

Declaration of conflicting interests

Funding

ORCID iD

Supplemental Material

References

Supplementary Material

Preparation of composites incorporated with complex sizes of Al₂O₃

Sample	20-μm (wt%)	30-μm (wt%)	50-μm (wt%)	70-μm (wt%)	Total amount (wt%)
1	0	0	50	25	75
2	0	0	25	50	75
3	0	25	0	50	75
4	0	25	50	0	75
5	0	25	25	25	75
6	0	50	0	25	75
7	0	50	25	0	75
8	25	0	0	50	75
9	25	0	25	25	75
10	25	0	50	0	75
11	25	25	0	25	75
12	25	25	25	0	75
13	50	0	0	25	75
14	50	0	25	0	75
15	50	25	0	0	75
16	25	50	0	0	75
PE	0	0	0	0	0
S20	75	0	0	0	75
S30	0	75	0	0	75
S50	0	0	75	0	75
S70	0	0	0	75	75