Preparation of Thermally Conductive Polymer Composites with Good

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Preparation of Thermally Conductive Polymer Composites with Good Electromagnetic Interference Shielding Efficiency Based on Natural Wood-Derived Carbon Scaffolds Ziming Shen, and Jiachun Feng ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/ acssuschemeng.8b06661 • Publication Date (Web): 15 Feb 2019 Downloaded from http://pubs.acs.org on February 19, 2019

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ACS Sustainable Chemistry & Engineering

Preparation of Thermally Conductive Polymer Composites with Good Electromagnetic Interference Shielding Efficiency Based on Natural Wood-Derived Carbon Scaffolds Ziming Shen, and Jiachun Feng*

State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, Fudan University, No.220, Handan Road, Shanghai 200433, China. *Corresponding author. E-mail: [email protected]. Tel: 86 (21) 3124 3735. Fax: +86 (21) 3124 2888. KEYWORDS: natural wood, carbon frameworks, polymer composite, thermal conductivity, electrical conductivity, electromagnetic interference shielding.

ABSTRACT: In modern electronic industry, multifunctional polymer composites associated with heat removal and electromagnetic shielding are highly needed. This work reported a method to fabricate epoxy composites with high electromagnetic interference shielding effectiveness (EMI SE) and thermal conductivity (TC) using natural wood as a starting material via backfilling epoxy into wood-derived carbon scaffolds. The results showed that after carbonization at 1200 oC, the carbon scaffolds could be well-maintained, which could serve as thermally and electrically conductive pathways in the composites. The resultant composites at the carbon loading of 7.0 vol % possessed a high TC of 0.58 W/(m∙K), an electrical 1 ACS Paragon Plus Environment

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conductivity of about 12.5 S/m and an average EMI SE of 27.8 dB over the X-band at the thickness of only 2 mm. Our work proposed a promising strategy to use the cost-effective and green materials to fabricate multifunctional polymer composites.

INTRODUCTION As communication instruments and portable electronic devices are widely used, electromagnetic interference (EMI), which is not only adverse to normal operation of the devices but also harmful for the health of human beings, has become an important concern in the modern world.1-2 High-performance EMI shielding materials play a crucial role in shielding technology, which is the key to control or mitigate electromagnetic radiation pollution.3-4 In addition to high EMI shielding property, high thermal conductivity (TC) is other crucial requirements for electronic material, which could promptly transfer excess heat from the heated device to surroundings.5 Traditional metallic materials, such as metal sheets, felts and meshes, can simultaneously exercise the roles.6 But their high density, poor corrosion resistance and high cost limited their practical applications.6-7 Thanks to the inherent advantages of polymers such as lightweight, corrosion resistance and process convenience, preparation of multifunctional polymer composites for efficient EMI shielding and heat removal have recently attracted much attentions.8-11 Unfortunately, polymers are mostly insulating in nature and transparent to electromagnetic waves. To endow them good EMI shielding effectiveness (SE), a convenient method was proposed to prepare conductive polymer composites filled with electrically conductive fillers.12 Taking into account production cost, mechanical properties and process conveniences, preparation of composites with high electrical conductivity (EC) at low filler loadings is a hot research topic.13 2 ACS Paragon Plus Environment

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Recently, the preparation of composites by backfilling polymers into pre-constructed electrically conductive filler networks has been demonstrated a promising strategy to achieve high EC at minimized concentration of fillers due to the fact that interconnected networks could serve as fast transport channels for charge carries.13-15 For example, Zhao et al. constructed interconnected rGO/SWCNT skeletons and then filled into PDMS matrix to prepare PDMS composites with the EMI SE of 31 dB at the 0.38 wt % CNTs loading.13 Chen et al. obtained pure CNT sponges via a CVD method and then prepared epoxy (EP)/CNT composite with a high EC of 148 S/m and EMI SE of around 33 dB with 0.66 wt % CNT loadings.14 On the other hand, as electrically conductive fillers are usually good thermally conductive fillers, some researches have succeeded in improving the TCs of composites by the analogical method.16-17 For example, Lian et al. prepared a 3D vertically aligned graphene network and then obtained epoxy composite with a high through-plane TC of 2.13 W/(m∙K) at an graphene loading of 0.92 vol %.16 Based on the open literature, it might be expected that this backfilling polymers into pre-constructed filler networks method could become an efficient approach to achieve the composites with simultaneously high TC and EMI SE at low filler loadings. Trees are the most abundant biomass on earth and wood has been widely used in the traditional fields, such as cellulose manufacturing, energy management materials and water filtration.18-19 The researchers found that mesoporous wood has aligned micro-channels that are mostly composed of cellulose nanofibers (CNFs) along the growth direction, which serve as paths for the transport of water, ions and other nutrients.18 Utilizing this intriguing structure, a series of high-performance materials have recently been fabricated and applied in some emerging areas, such as transparent films,20-21 water treatment,22-24 electronic devices,25 and 3 ACS Paragon Plus Environment


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sensors26. For example, Hu’s group utilized natural wood to prepare a series of solar steam devices for water purification.22-24 They found that the aligned micro-channels could provide pathways for continuous water pumping and escaping and therefore the devices possessed high efficiency. Tang et al obtained the de-lignified wood slice and then backfilled EP to prepare flexible transparent films, which could be used as screen protection films of cell-phones.21 In regard to preparation of polymer composites with high TC and EMI SE using wood (biomass) as a starting material, some works have been carried out. For example, Chen et al. impregnated the polyamide-imide (PAI) into the delignified wood scaffold and then carbonized at a low temperature (313 oC) to obtained PAI/wood composite. They found that at low temperature, the coating PAI could be well-maintained and the composite possessed a through-plane TC of 0.56 W/(m∙K).27 Li et al. used carbonized loofah fiber/graphene hybrids as electrically conductive filler to fabricate polyether-ether-ketone composites with the EMI SE of 27.1 dB.28 These pioneering works inspired us to deliberate whether we could utilize natural wood to fabricate electrical conductive networks with aligned structures and then to backfill into polymer matrix to prepare composites with simultaneously high TC and EMI. However, to our knowledge, no attempt has been made in the open literatures. In this work, we reported a strategy to fabricate interconnected carbon scaffold from natural wood via a sequential delignification and carbonization process and then backfilled into EP matrix to prepare EP/carbon composites with high TC and EMI SE. The resultant composite exhibited a TC of 0.58 W/(m∙K), an EC value of 12.5 S/m and an average EMI SE of 27.8 dB at a small thickness of 2 mm over the X-band frequency range (higher than the commercial requirement of 20 dB). This method to fabricate multifunctional composites based on natural 4 ACS Paragon Plus Environment

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materials conformed to the sustainable development pattern, which would possess high potential as thermal management components and EMI shielding elements. EXPERIMENTAL SECTION Materials. The wood used in this study was produced by pine tree growing on the North China Plain. Sodium chlorite and glacial acetic acid were purchased from Aladdin Reagent Corp. Epoxy resin was purchased from Bluestar Wuxi Petrochemical Co. Ltd. (Jiangsu, China). 4, 4'-methylene bis(2-chloroaniline) (MOCA), curing agent of epoxy, was purchased from Aladdin Reagent Corp. Fabrication of carbon scaffolds. The wood-derived carbon scaffold was prepared according to previous studies21, 26, which included sequential delignification and carbonization, as illustrated in Figure 1. In the first delignification process, a piece of wood slice was obtained by cutting the wood block perpendicular to tree growth direction and immersed in a boiling solution of sodium chlorite (2 wt %) in glacial acetic acid buffer (pH 4-5). After wood slice turned white and then were washed several times with water, the dried de-lignified wood framework was obtained by a freeze-drying process. As the framework was mostly made of cellulose nanofibers, we coded it as “CNF”. In the following carbonization, the CNF framework was pyrolyzed in a tubular furnace at 800 and 1200 oC for 2 h in a nitrogen atmosphere to obtain carbon scaffolds with different graphitic degrees, respectively, which were coded as “C800” and “C1200”. Preparation of EP/Carbon Composites. The EP/carbon composites were prepared via the vacuum-assisted infiltration of EP into carbon scaffolds. First, curing agent (MOCA) was uniformly dissolved in EP resin monomer (weight ratio of 1:3) under vigorous stirring at 100 5 ACS Paragon Plus Environment


oC.

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Subsequently, the prepared carbon scaffolds were immersed into the EP resin mixture and

then transferred into a vacuum oven at 110 oC for 30 min to remove the air. After that, the EP composite was cured at 150 oC for 2 h and 180 oC for another 2.5 h. The extra EP matrix adhered on the composites surface was removed by polishing. The obtained EP composites were designated as EP/C800 and EP/C1200, respectively. For comparison, pure EP and EP/CNF composites were also prepared by an identical process.

Figure 1. Schematic to the fabrication of carbon scaffolds and EP/carbon composites. Characterizations. The X-ray diffraction (XRD) patterns were recorded on an X’pert diffractometer (PANalytical, Netherlands) using Cu Kα radiation. Scanning electron microscopy (SEM) images were observed using an Ultra 55 field-emission scanning electron microscopy (Zeiss, Germany). X-ray photoelectron spectroscopy (XPS) was conducted with an Escalab 250XI electron spectrometer (Thermo Fisher) with monochromatic 150 W Al Kα radiation. Fourier transform infrared spectroscopy (FTIR) of CNF and carbon scaffolds was measured by a Nicolet 6700 spectrometer (Thermo Fisher) at 4000-400 cm−1 frequency range. The through-plane TCs of EP and EP composites were examined according to our previous reported method.29 The electrical conductivities of EP composites were measured by a four6 ACS Paragon Plus Environment

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probe tester (Suzhou Jingge Electronic Co., China). The tensile properties of composites were evaluated using a universal testing machine (SANS, China) with a speed of 2 mm/min. EMI SE of the prepared EP composites over the X-band frequency range was measured using a N5242A vector network analyzer (VNA) (Agilent Technologies). A pair of holders were used for holding the samples with the size of 22.5 mm × 10.0 mm × 2 mm. Holders were connected to two coaxial to waveguide adaptors, which were connected to VNA with two coaxial cables. During the testing, the S-parameters of each sample including S11 and S12 were recorded. Then the EMI SE can be calculated as follows: SET = -10 log (Pout/Pin) = -20 log |S21|; SER = -10 log (1-|S11|2), where SET and SER were total and reflective EMI SE, respectively.30-31 RESULTS AND DISCUSSION Fabrication of Carbon Scaffolds. The preparation of graphitized carbon scaffolds using natural wood as a starting material included a sequential delignification and carbonization process. As the used wood slice was obtained by cutting the wood block perpendicularly to the longitudinal direction (tree growth direction), the growth rings could be obviously seen (Figure 1). It showed pale yellow color owing the light absorption capability of lignin19. After delignification in acidic NaClO2 solution, the CNF framework was obtained and it turned yellow to white (Figure 2a). Further carbonization at an N2 atmosphere, the CNF scaffold was carbonized into black carbon scaffold (Figure 2b). Considering the issue of energy consumption, we firstly prepared C800 under a carbonization temperature of 800 oC. When a piece of the C800 scaffold was connected into a closed circuit (Figure S1), we found that the bulb could shine, which suggested high electrical conductivity (EC) of graphited carbon scaffolds. The obtained CNF and carbon scaffolds possessed relatively high strength and could 7 ACS Paragon Plus Environment


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be freestanding (Figure 2a and b insert), which was propitious for the networks to be well retained in the following EP composites. By cutting the wood with different dimensions, carbon scaffolds with different dimensions could be easily achieved (Figure 2c), which was beneficial for application in different electronic devices. To demonstrate the carbonization of CNF, the chemical structures of CNF and carbon scaffolds were comparatively studied by a series of XRD, FTIR, XPS and Raman analysis (Figure 2 d-g). On the XRD pattern of CNF, two peaks at 15.6 and 22.4o could be obviously seen, which was corresponded to the characteristic (110) and (200) diffraction planes of cellulose nanofibers. This results demonstrated the lignin was successfully removed and most of residues were cellulose nanofibers. In contrast, on the XRD pattern of C800, these two peaks disappeared and another broad peak at about 22.6o appeared, which corresponded to the characteristic peak of graphene, suggesting the CNF translated into graphited carbon under a high temperature. Compared with that of raw de-lignified wood, the aromatic skeletal vibration peak of benzene ring at 1506 cm-1 in lignin disappeared on the FTIR spectrum of CNF, which demonstrated again the lignin was removed after the delignification treatment.19 While on the FTIR spectrum of C800, there was almost no any peaks existing, which also demonstrated the carbonization of CNF. We used XPS to verify again that the carbonization of CNF under high temperature. On the XPS spectra of CNF, there obviously existed C1s and O 1s peak. Compared with that of CNF scaffold, the C1s peak increased while O 1s peak decreased significantly on the C800, which implied the removal of functional groups and the CNF was carbonized.

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Figure 2. Photos showing (a) CNF and (b, c) carbon scaffolds; (d) XRD patterns, (e) FTIR, (f) XPS and (g) Raman spectra of CNF and carbon scaffolds. To study the effect of the carbonization temperature on the graphitization degree of carbon scaffold, we prepared another carbon scaffold under a higher temperature, C1200. It was found that the C 1s peak of C1200 further increased compared than that of C800, which suggested a higher graphitization degree at higher carbonization temperature. The determined C/O ratio results showed that the ratio of C800 and C1200 were 14.4 and 37.0, respectively, which demonstrated again the higher graphitization degree under higher temperature. The Raman spectroscopy is a classical tool for analyzing carbon materials to check their microscopic structures of carbon scaffolds.32 The G band at about 1350 cm-1 corresponded to the large graphite crystals while the D band at about 1575 cm-1 corresponded to disordered carbon or defective graphitic structures.33 The relatively intensity of the G/D bands (IG/ID), as calculated by the height of peaks, can be used as an indication of the crystalline carbon structures.33 On 9 ACS Paragon Plus Environment


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the Raman spectra of both C800 and C1200 the characteristic D and G peaks existed. Their IG/ID ratio results showed that the former possessed a value of 0.98 while the latter had a higher value of 1.03, which also demonstrated that C1200 exhibited a higher graphitization degree compared that of C800. The micro-structures of CNF and carbon scaffolds were studied by FESEM. As the wood slices were obtained by cutting the wood block perpendicularly to tree growth direction, the vertically aligned micro-channels could be maintained. After the remove of lignin, the even and well-defined pore structures with the dimension of about 40 um remained in the CNF scaffold, as shown in Figure 3a. From the longitudinal direction SEM image (Figure 3b), we could see that the cell wall made of cellulose nanofibers arrayed along the microchannel direction and whole CNF scaffold possessed a honeycomb-like microstructure. After the carbonization of CNF, the obtained carbon scaffolds still remained a similar honeycomb-like structure (Figure 3c,d). Differently, the dimensions of the pores became smaller. The remained pores were helpful for backfilling of EP to prepare composites with few defects.

Figure 3. (a, c) Top-view and (b, d) longitudinal direction SEM image of CNF and C800, respectively. 10 ACS Paragon Plus Environment

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EMI SE and TCs Properties of EP composites. By impregnation of CNF and carbon scaffolds into EP matrix, corresponding EP composites were obtained. As shown in Figure 4a, pure EP exhibited translucent yellowish-green color. EP/CNF composite showed yellow color and the growth rings of wood could be obviously seen, which demonstrated that the vertically aligned CNF scaffold could be well maintained in the EP matrix to some extents. As with two EP/carbon composites, they showed black color due to the fact that the carbon scaffolds were black. The SEM images of EP/CNF and EP/C800 composites further verified well-maintained CNF and carbon walls. As shown in the red lines of Figure 4b and c, the vertically aligned CNF and carbon networks could be clearly observed. The well-maintained carbon scaffolds could serve as thermally and electrically conductive pathways, which was helpful for the TCs and ECs improvement of the composites.

Figure 4. (a) Photo showing the EP composites and pure EP; SEM images of (b) EP/CNF and (c) EP/C800 composites. To investigate the effect of graphitic carbon scaffolds on the electrical properties of EP composites, their electrical conductivities (ECs) were examined, as shown in Figure 5. Pure EP exhibited excellent electrical insulation and its EC was as low as 5×10-13 S/m. After the CNF 11 ACS Paragon Plus Environment


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scaffold was encapsulated into EP matrix, the obtained EP/CNF composite showed a slightly increased EC (1.0×10-11 S/m), which might be related that CNF had a low electrically resistivity due to its high crystalline structure.34 As expected, the carbon frameworks filled composites possessed a significantly increased EC compared with that of EP/CNF composite. For the C800 filled composite, the EC value of EP-C800 reached 6.0 S/m. The EP/C1200 with higher graphitic degree further increased to 12.5 S/m, which suggested that higher graphitic degree of carbon scaffold, the higher EC of its composite. From the TGA results (Figure S2), we determined that carbon contents of two composites were only ~7.0 vol % (Table S1). Such high conductivity at low loadings could be attributed to well-maintained conductive carbon network in the EP composites, which has been demonstrated by SEM image (Figure 4c). High EC was a prerequisite for polymer composites to possess good EMI SE performances. The EMI SE values of two EP/carbon composites and pure EP measured over the X-band frequency ranges were shown in Figure 5b. We could see that due to its electrical insulation, EP was transparent to electromagnetic waves and its EMI SE was almost zero at the thickness of 2 mm. While for two EP/carbon composites at the same thickness, they exhibited good EMI SE properties. For EP/C800 composite, its average EMI SE value was about 19.8 dB. As with EP/C1200 with higher EC, its average EMI SE value further increased and it reached as high as 27.8 dB, indicating that above 99% of the electromagnetic radiation was blocked by the shielding material35. It is well accepted that EMI SE value of at least 20 dB is typically required for conductive polymer composites to be commercially applicable in EMI shielding devices.35 The EMI SE of EP/C1200 was apparently higher than this requirement, which suggested our prepared EP/carbon composite possessed high potential in the practical application. Moreover, 12 ACS Paragon Plus Environment

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we compared the EMI SE value for EP/C1200 with the reported un-foamed polymer composites filled with other carbonaceous fillers in the open literature. As presented in Table 1, we found that the normalized SE value of EP/C1200 composite was comparable to most of reported values.

Figure 5. (a) EC of EP and EP composites; (b) EMI SE of EP and EP/carbon composites over the frequency of 8–12 GHz. Table 1. Comparison of EMI SE of our EP/C1200 composite with un-foamed polymer composites filled with other carbonaceous fillers in the open literature. Composite

Filler loadings

PDMS/rGO/SWCNTs EP/CNTs EP/Graphene PS/rGO PS/MWCNTs PA6/EG EP/Graphene PVDF/CNTs PP/CNTs EPDM/CB PU/Graphene PMMA/Graphene PVDF/MWCNTs PVDF/CNTs PC/CNTs EP/Carbon

0.28 wt % 0.66 wt % 0.33 wt % 4.0 wt % 20 wt % 2.27 vol % ~1.0 wt % 3.0 wt % 5.0 vol % 35 wt % 5.0 vol % 2.6 vol % 7 wt % 3.5 wt % 5.0 wt % ~7.0 wt %

Thickness (mm) 2.0 2.0 2.0 2.5 2.0 2.0 3.0 1.1 2.8 5.5 2.0 2.9 2.0 1.1 1.85 2.0

SE (dB) 31.0 33.0 27.0 31.5 30.0 25.0 30.0 16.7 25.0 20.0 32.0 63.2 30.9 20.3 25 27.8

The normalized SE (dB/mm) 15.5 16.5 13.5 12.6 15.0 12.5 10.0 15.2 8.9 3.6 16.0 21.8 15.5 18.4 13.5 13.9

Ref. 13 14 15 35 36 37 38 39 40 41 42 43 44 45 46 This work 13

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To understand the shielding mechanisms of EP/C1200 composites, we tried to propose possible explanations from the standpoints of factors affecting EMI SE. The total EMI SE (SET) attenuating mechanisms are consisted of reflection (SER), absorption (SEA) and multiple reflections (SEM). It can be expressed by the equation: SET=SER+SEA+SEM.47-48 The reflection of wave relates to the impedance mismatch between the air and the shielding materials, resulting from the interaction of charged particles (free electrons or holes) of a conductor in the electromagnetic field.6 Absorption in a shielding material chiefly stems from Ohmic loss, which is dissipation of energy by free charge carriers through direct contact conduction, hopping and tunneling mechanisms.39, 45 The multiple-reflection relates to the internal nonuniformity of a shielding material, which is usually neglected when SET >10 dB.48 For EP/C1200 composite, the value of SET (27.8 dB) was far higher than >10 dB and thus the SEM was neglected. Based on this point, SEA and SER for EP/C1200 were calculated from the measured scattering parameters (S11 and S21) according to the following equations: SET = 20 log |S21|; SER = -10 log (1-|S11|2); SEA=SET-SER.30-31 As presented in Figure 6a, the average SET, SEA, and SER were 27.8, 26.7, and 1.1 dB, respectively, which suggested that the shielding effect for the EP/C1200 was mainly contributed to the absorption mechanism. Figure 6b visually illustrated the EMI-shielding process of EP/C1200 composite. The dominated absorption and little reflection might be related to the interconnected conductive carbon scaffolds in the composite.49 As the existence of honeycomb-like carbon scaffolds could effectively decrease the impedance mismatch between the EP composite and air interfaces, when the incident microwaves hit the surface, the insulting EP impregnated in the carbon micro-tubes enabled most EM wave deep penetration into the EP composites, thus greatly 14 ACS Paragon Plus Environment

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weakening the surface reflection.13, 43, 50 Similar results have been found in graphene/carbon nanotube frameworks filled PDMS composites.13 On the other hand, the well-maintained carbon micro-channels facilitated substantial attenuation of the incoming EM waves by repeated dissipation (absorption) and multiple reflections (scattering) along the individual (red arrow in Figure 6b) or adjacent micro-channels (blue arrow).49 Hence, the most incident microwaves have been absorbed and dissipated so that only an extremely tiny part could traverse the composites, yielding a highly efficient EMI-shielding performance.

Figure 6. (a) SET, SER, and SEA of EP-C1200; (b) Schematic description of electromagnetic wave transfer across EP-C1200. The through-plane TCs of EP composites were also examined, as presented in Figure 7a. Pure EP had a low TC of 0.16 W/(m∙K), which was in accord with the reported value.51-52 For EP/CNF composite, it exhibited an increased TC of (0.39 W/(m∙K)). Generally, a material’s TC was related to three factors, thermal diffusivities (α), density (ρ) and specific heat capacity (Cp). It can be calculated by this equation: TC=α×ρ×Cp.29 As presented in Table S2, for the EP/CNF composite, due to the slightly increased a, ρ and Cp values, the calculated TC value improved. We could see that for two EP/carbon composites, the TCs increased compared with EP and EP/CNF composite. For EP/C800, its TC value reached 0.52 W/(m∙K) and for EP/C1200, it reached 0.58 W/(m∙K). Their enhancements were because the CNF scaffold was 15 ACS Paragon Plus Environment


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carbonized into conductive carbon scaffold, which could serve as thermally conductive pathways to directly transmit the heat across the composites (Figure 7b). As listed in Table S1, even though of the ρ and Cp values slightly declined, the α value of EP/carbon composites increased significantly. The α value of EP/CNF was 0.21 mm2/s while those of EP/C800 and EP/C1200 increased to 0.35 and 0.39 mm2/s, respectively. So that the calculated TCs of EP/carbon composites improved compared than EP/CNF composite. The higher TC of EP/C1200 composite might be ascribe to higher graphitic structure of C1200, which was beneficial for improvement of the α value.

Figure 7. (a) TCs of EP and EP composites; (b) Schematic description of the heat flow across EP-C composites. The mechanical test revealed that although the mechanical performance of composite was inferior to pure EP, the tensile strength of EP/C1200 composite could reached 24.9 MPa and its elongation at break was 5.4% (Figure S3). The EP/C1200 composite could easily support the weight of 100 times that of itself (Figure S4). Relatively high strength was important for its practical application. On the basis of above results, the EP/carbon composites based on the cost-efficient and abundant wood showed favorable strength, remarkable EMI SE and high TC, which would possess potential in thermal management and EMI shielding elements.


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CONCLUSION In this work, we fabricated carbon scaffolds based on natural wood via a sequential delignification and carbonization process and then used them to prepare EP/carbon composite with high TC and EMI SE. The interconnected carbon micro-channels could be well maintained after the carbonization process. We also found that the higher carbonization temperature, the higher graphitic degree of carbon scaffold. Accordingly, the resultant EP/carbon composite possessed higher TC and better EMI SE. The TC value of EP/C1200 composite reached 0.58 W/(m∙K) and its average EMI SE was 27.8 dB at 8–12 GHz when the thickness was only 2 mm, which was higher than the requirement for commercial applicable in EMI shielding devices (20 dB). This study provided a promising strategy to multifunctional polymer composites with high TC and good EMI SE based on cost-efficient and abundant wood, which would exhibit high potential for thermal management components and EMI shielding elements in advanced electronic areas. ASSOCIATED CONTENT Supporting Information. Figure S1. Photo showing the bulb shining when the C800 was connected in a close circle. Figure S2. TGA curves of EP and EP-C composites. Figure S3. (a) The typical tensile curves of pure EP and EP/C1200 composite; (b) Photo showing EP/C1200 could support the weight of 100 times that of itself. Table S1. The residues at 700 oC (R700), weight (W) and volume loading (V) of carbon in the EP and EP composites. Table S2. The density (ρ), specific heat capacity (Cp) through-plane thermal diffusivities (α), 17 ACS Paragon Plus Environment


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calculated thermal conductivities (TCs) of EP and EP composites. AUTHOR INFORMATION Corresponding Author * (J.F) E-mail: [email protected]; Tel +86-21-31243735. ORCID Jiachun Feng: 0000-0002-9410-7508; Ziming Shen: 0000-0002-5497-2863 Author Contributions The manuscript was written through contributions of all authors. Notes The authors declare no competing financial interest. Reference (1) Bera, R.; Maitra, A.; Paria, S.; Karan, S. K.; Das, A. K.; Bera, A.; Si, S. K.; Halder, L.; De, A.; Khatua, B. B. An Approach to Widen the Electromagnetic Shielding Efficiency in PDMS/Ferrous Ferric Oxide Decorated RGO-SWCNH Composite through Pressure Induced Tunability. Chem. Eng, J. 2018, 335, 501-509. (2) Jia, L.-C.; Yan, D.-X.; Jiang, X.; Pang, H.; Gao, J.-F.; Ren, P.-G.; Li, Z.-M. Synergistic Effect of Graphite and Carbon Nanotubes on Improved Electromagnetic Interference Shielding Performance in Segregated Composites. Ind. Eng. Chem. Res. 2018, 57, 11929-11938. (3) Verma, P.; Saini, P.; Malik, R. S.; Choudhary, V. Excellent Electromagnetic Interference Shielding and Mechanical Properties of High Loading Carbon-Nanotubes/Polymer Composites Designed Using Melt Recirculation Equipped Twin-Screw Extruder. Carbon 2015, 89, 30818 ACS Paragon Plus Environment

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TOC

Utilizing natural wood as a starting material, thermally conductive polymer composites with good electromagnetic interference shielding efficiency were prepared.


Preparation of Thermally Conductive Polymer Composites with Good

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