Polydimethylsiloxane Composites Research Articles

Enhancement of thermal conductivity in PDMS/CFP composites using a dredging-plugging thermal network

In the preparation of thermally conductive polymer composites (TCPC), it is necessary to incorporate a filler network in the polymer matrix. Further enhancement of the thermal conductivity (TC) of TCPCs is challenging due to the exceptional heat absorption of the polymer matrix, which results in heat flow losses in the network. To address this issue, a novel procedure, termed thermal network dredging-plugging, has been proposed. In this study, polydimethylsiloxane (PDMS) composites with a carbon fiber powder (CFP) network and a CFP/glass ball (GB) network enhanced by dredging-plugging were prepared by a coating method. The TC of the PDMS/CFP system increased with an increase in CFP loading from 0 to 12 wt% and a decrease in sample thickness from 0.4 to 0.2 mm. At a 12 wt% CFP loading, the PDMS/CFP composites exhibited a maximum TC of 4.687 W/(mK). With the addition of GBs ranging from 0 to 2 wt%, the dredging-plugging CFP/GB network increased the maximum TC by a factor of 1.26 relative to the dredged CFP network. In conjunction with the thermal resistance method, a mathematical model that considers both the plugging and dilution effects of GBs was constructed. The calculated TCs were validated by using the prepared PDMS/CFP/GB composites, with average absolute relative errors ranging from 0.5 % to 4.19 %. In addition to TC enhancement, the mechanical properties and thermal management of the PDMS composites were evaluated.

Contribution to the percolation threshold study of Silicon carbide filled polydimethylsiloxane composites used for field grading application

The correlations between the electrical behavior and microstructural properties of samples consisting of particle composites fabricated from SiC particles embedded in a silicone matrix, were investigated using X-ray computed tomography. In the voltage field range 200-1000 V/mm, the measured conductivity as a function of SiC volume fraction exhibits two distinct gaps. Upon further investigations, we attribute these observations to percolation thresholds at the microscale. The first gap, corresponding to interconnections between SiC particles that were originally disconnected, is more significant at higher voltage; while the second one, resulting from shortening conductivity pathways between the external surfaces of the samples with the increase of SiC volume fraction, seems more sensitive to lower voltages and is correlated with a decrease of the tortuosity of the percolated SiC network.

Environmentally Friendly High‐Performance Polydimethylsiloxane Composites Reinforced with Renewable Cellulose Nanocrystals Based on Dynamic Silyl Ether Linkages

AbstractEnvironmentally friendly high‐performance composites made from either reprocessable polymer matrix or renewable fillers have become increasingly significant in order to reach a sustainable future. Herein, polydimethylsiloxane/modified cellulose nanocrystals (PDMS/mCNC) composites showing outstanding mechanical and reprocessable properties via silyl ether linkages are prepared. With only 1 wt% mCNC, the PDMS/mCNC composite exhibits the tensile strength of 2.96 MPa, which is twice that of the pure PDMS elastomer, while the toughness can achieve 7.32 MJ m−3. Remarkably, the reprocessing efficiency can be as high as 100% even for triple reprocessing process. Additionally, the favorable effect of mCNC on constructing hybrid filler network within vitrimers is explored for the first time. Selection of boron nitride nanosheet (BNNS) as the functional filler, 40 wt% BNNS is uniformly dispersed by only a small amount of mCNC and a homogeneous thermally conductive network is built, with the thermal conductivity of the PDMS/mCNC@BNNS composite increasing remarkably to 2.901 W m−1 K−1. In a word, this work paves the way to develop sustainable, mechanically strong, and reprocessable composites with mCNC as a renewable bio‐filler.

Comprehensive Investigation of the Temperature-Dependent Electromechanical Behaviors of Carbon Nanotube/Polymer Composites.

The performances of flexible piezoresistive sensors based on polymer nanocomposites are significantly affected by the environmental temperature; therefore, comprehensively investigating the temperature-dependent electromechanical response behaviors of conductive polymer nanocomposites is crucial for developing high-precision flexible piezoresistive sensors in a wide-temperature range. Herein, carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composites widely used for flexible piezoresistive sensors were prepared, and then the temperature-dependent electrical, mechanical, and electromechanical properties of the optimized CNT/PDMS composite in the temperature range from -150 to 150 °C were systematically investigated. At a low temperature of -150 °C, the CNT/PDMS composite becomes brittle with a compressive modulus of ∼1.2 MPa and loses its elasticity and reversible sensing capability. At a high temperature (above 90 °C), the CNT/PDMS composite softens, shows a fluid-like mechanical property, and loses its reversible sensing capability. In the temperature range from -60 to 90 °C, the CNT/PDMS composite exhibits good elasticity and reversible sensing behaviors and its modulus, resistivity, and sensing sensitivity decrease with an increasing temperature. At room temperature (30 °C), the CNT/PDMS composite exhibits better mechanical and piezoresistive stability than those at low and high temperatures. Given that environmental temperature changes have significant effects on the sensing performances of conductive polymer composites, the effect of ambient temperature changes must be considered when flexible piezoresistive sensors are designed and fabricated.

A mechanically strong and highly thermally conductive graphene skeleton constructed by polyamide acid welding and syneresis for polydimethylsiloxane composites

A mechanically strong and highly thermally conductive graphene skeleton constructed by polyamide acid welding and syneresis for polydimethylsiloxane composites

Soft and stretchable protective substrates for wearable thermal managements: Polydimethylsiloxane (PDMS) composites containing paraffin microcapsules with silica nanoshells

Wearable thermal management has attracted extensive attention of researchers and clinicians due to their great potential application in the field of wearable and smart electronic device. In this research, the flexible PCMs composites as soft and stretchable protective substrates have been prepared for wearable thermal management through simple mixing and curing process of PDMS and paraffin encapsulated inside silica nanoshell (paraffin microcapsules). Systematic experiments have been carried out to illustrate the stress-strain curves, thermal insulating performance, stretchability and other properties varying with temperature. The obtained PDMS composite (P10M7, 7 g paraffin microcapsules in 10 g PDMS matrix) was soft and stretchable which can be subjected to complex deformations (such as stretch, twist, stretch/twist) over 100 % without failures. The silica nanoshells of paraffin microcapsules can not only avoid the leakage of paraffin during solid-liquid phase transition process, but also act as the support reinforced shell to maintain the mechanical properties upon paraffin melting point. Furthermore, the infrared thermal imaging research shown that PDMS composites with paraffin microcapsules exhibited faster temperature increment than PDMS composite with neat paraffin for the good compatibility between PDMS matrix and paraffin microcapsules which can reduce interface thermal resistance and improve thermal conduction during heating procedure. This study provides a feasible strategy to design and fabricate flexible PCMs composites for wearable thermal management device.

Stretchable Multifunctional Polydimethylsiloxane Composites with Cage‐Like Conductive Architecture for Integrated Thermosensitive and Electromagnetic Interference Shielding Performance

AbstractHigh‐performance sensors with outstanding sensitivity, wide working range, and multifunctional properties are highly desirable in modern integrated smart wearable electronics. Herein, polydimethylsiloxane (PDMS)‐based stretchable pyroresistive sensors composed of tightly‐assembled silver nanowires (Ag NWs)‐encapsulated PDMS microspheres (PM) and expandable microspheres (EM) are fabricated. The synergistic cage‐like conductive network and EM endow the temperature sensor with tunable sensitivity (Max TCR: 27.4% °C−1), broad sensing range (25–85 °C), low perception limit (0.1 °C), and excellent anti‐interference ability. Interestingly, at elevated temperature field (> 90 °C), a remarkable conduction‐insulation transition is observed, which is employed to facilitate an early fire alarm system. In addition, the selectively distributed Ag NWs constructs segregated conductive pathways at an ultralow content (Pc = 0.014 vol%), leading to efficient electromagnetic interference shielding (40.0 dB). The underlying mechanism responsible for the observed superior thermosensation and EMI shielding performance is elucidated, and possible applications are demonstrated. Consequently, this work offers a novel strategy for the design of flexible, multifunctional pyroresistive sensors toward artificial intelligence and emerging wearable electronics.

Facile superhydrophobic modification on HPMC film using polydimethylsiloxane and starch granule coatings

The excessive water sensitivity of hydroxypropyl methylcellulose (HPMC) films prevent them from being used extensively. In order to overcome this limitation, superhydrophobic HPMC films were meticulously crafted through the utilization of a composite of polydimethylsiloxane (PDMS) and ball-milled rice starch, corn starch, or potato starch (RS/CS/PS) for the coating process. Initially possessing hydrophilic properties, the HPMC Film (CA = 49.3 ± 1.8°) underwent a transformative hydrophobic conversion upon the application of PDMS, resulting in a static contact angle measuring up to 103.4 ± 2.0°. Notably, the synergistic combination of PDMS-coated HPMC with ball-milled starch demonstrated exceptional superhydrophobic attributes. Particularly, the treated HPMC-based film, specifically the HP-CS-2 h film, showcased an impressive contact angle of 170.5° alongside a minimal sliding angle of 5.2°. The impact of diverse starch types and the ball milling treatment on the PDMS/starch coatings and HPMC film was thoroughly examined using scanning electron microscopy (SEM), wide-angle X-ray diffraction (WAXS), and particle size analysis. These studies demonstrated that the low surface energy and roughness required for the creation of superhydrophobic HPMC-based films were imparted by the hierarchical structure formed by the application of PDMS/ball-milled starch. Chemical compounds studied in this articlePolydimethylsiloxane (PubChem CID: 24764); Hydroxypropyl methylcellulose (PubChem CID: 671); Ethyl acetate (PubChem CID: 8857).

Efficient preparation of polydimethylsiloxane‐based phase change composites with sandwich structure

AbstractWith the rapid development of portable electronic devices, there is an urgent need for the multifunctional composites like excellent electromagnetic interference (EMI) shielding performance, mechanical property, and thermal management capabilities. Here, due to the low thermal conductivity of phase change materials (PCMs), a sandwich structure carbon nanotube/phase change microcapsule/carbon nanotube (CNT/PMC/CNT (CPC)) film was prepared by vacuum‐assisted filtration (VAF) method. CNT, PMC, and cellulose nanocrystal (CNC) were used as functional fillers. The addition of CNCs was used to improve the mechanical performance of CPC film. Compared with PMC‐CNC (PC) film, CPC film with sandwich structure prevented leakage phenomenon efficiently. Subsequently, the use of ultrasonic‐assisted forced infiltration (UAFI) successfully infiltrated polydimethylsiloxane (PDMS) matrix in the filler skeleton to obtain CNT/PMC/CNT/PDMS (CPCP) composites. When filler mass ratio (CNT: CNC and PMC: CNC) reached 10:1, the thermal conductivity of CPCP composites was 2.32 W/(m·K) and total EMI shielding effectiveness (EMI SET) of it with 0.38 mm thickness reached 37.46 dB at 12.4 GHz. Besides, these sandwich composites exhibited the good mechanical properties and heat storage capacity. And we systematically observed the impact of different addition amounts of PC homogeneous dispersing solution on phase change ability of CPCP10:1 composites. In summary, CPCP phase change composites with sandwich structure shows potential application prospect in thermal management materials with EMI shielding of electronic devices.Highlight The sandwich structure CPCP composites prepared by the combination of VAF and UAFI method, showing superior thermal conductivity and phase change ability. CPCP has excellent EMI shielding performance, which can meet the need of TMMs with EMI shielding performance. Compared with same thickness PC film, sandwich CPC film can prevent leakage phenomenon efficiently.

Improving RFID performance through enhanced electromagnetic wave absorption with Fe2O3 and polytetrafluoroethylene-based bilayer polydimethylsiloxane composites

This study presents a bilayer polydimethylsiloxane (PDMS) composite microwave absorber, consisting of Fe2O3 and polytetrafluoroethylene (PTFE) fillers, to enhance the functioning of radio frequency identification (RFID) systems on conductive surfaces. The uniform Fe2O3/PDMS and PTFE/PDMS composites are prepared by mixing PDMS and respective filler through a desktop three-axis roller machine followed by curing at 80 °C for two hours. The composites are then joined to create a bilayer composite mat. The combination of a 70 wt% Fe2O3/PDMS composite with a 50 wt% PTFE/PDMS composite demonstrates the best performance. The Fe2O3/PDMS composite shows the high reflection loss of 47.98 dB and a total shielding of 4.1 dB, while the PTFE/PDMS composite exhibits the reflection loss of 47.0 dB and a total shielding of 0.6 dB. The optimized bilayer composite enables a tag recovery of approximately 87.57 %. These findings demonstrate its practical application in reducing interference and enhancing the RFID tag detection.

Black TiO2-infused polydimethylsiloxane composites for efficient solar-assisted water evaporation and thermoelectric energy generation

Solar assisted interfacial water evaporation through the strategic localization of solar- thermal energy conversion by relying on the air–water interface has garnered significant interest owing to its enhanced efficiency in a variety of applications, from water purification to energy generation. Nevertheless, achieving utterly improved thermal management to enhance the efficiency of solar heat consumption is still quite complex. Herein, we created special composites of black titanium dioxide and polydimethylsiloxane (B-TiO2/PDMS) aiming effectively harvest a broad range of spectrum of solar radiation for the benefit of improving energy production and aid for water purification. The B-TiO2/PDMS sponge possesses an impressive optical to thermal transformation as an outcome, keeping a constant surface temperature of 66 °C, as opposed to 41.6 °C for PDMS sponge at typical 1 sun intensity for 10 min. This solar evaporation system constitutes a greater evaporation rate of 1.39 Kg m−2h−1 with a photothermal conversion efficiency of 70.8 % under 1 sun illumination. To accomplish integrated thermoelectric power generation during solar evaporation, the thermoelectric (TE) module is used as an insulating medium, succeeding an optimal yield of 30 mV under 1 sun. Furthermore, the as prepared B-TiO2/PDMS sponge achieved notable mechanical resilience and incredible adaptability, offering a viable approach for thermal management and cooperative way to utilize solar powered evaporation to produce potable water and energy.

Enhancement of the mechanical properties in ultra-low weight SWCNT sandwiched PDMS composites using a novel stacked architecture

This study focuses on enhancing the mechanical properties of thin, soft, free-standing films via a layer-by-layer (LBL) fabrication process called LBL-FP. Soft polymer nanocomposite (PNC) thin films, combining polydimethylsiloxane (PDMS) and single-walled carbon nanotubes (SWCNT) at ultra-low loadings using a unique bottom-up LBL-FP, are examined. Two different structures of layered composites, (i) LBL PNCs- Layered composites with alternating layers of PDMS and SWCNT, (ii) Bulk PNCs- Layered composites with SWCNT dispersed in the bulk of PDMS, are comparatively investigated for their structural and mechanical properties. Silane-functionalized SWCNT strengthens the chemical bonding with PDMS, improving adhesion and dispersion. Mechanical analysis using nanoindentation, delamination, and dynamic analysis highlights the advantages of LBL PNCs with alternating layers of PDMS and SWCNT. Notably, LBL PNC (0.5 wt%) exhibits significant improvements, such as 2.6X increased nanoindentation resistance, 3X improved viscoelasticity, and (2–5)X enhanced tensile properties in comparison with neat PDMS. Due to this, LBL PNCs offer potential for soft, lightweight applications like wearables, electromagnetic interference shielding materials, and strain sensors while advancing composite thin film mechanics. The study emphasizes using a stacked architecture to produce PDMS-SWCNT multilayered PNCs with improved mechanics utilizing ultra-low concentrations of SWCNT. This first-of-its-kind stack design facilitates possibilities for lightweight composites utilizing less fillers. The LBL assembly involves the stacking of alternating layers of different materials, each contributing specific properties to enhance the overall strength and toughness of the structure.

Highly Thermally Conductive Polydimethylsiloxane Composites with Controllable 3D GO@f-CNTs Networks via Self-sacrificing Template Method

Highly Thermally Conductive Polydimethylsiloxane Composites with Controllable 3D GO@f-CNTs Networks via Self-sacrificing Template Method

A Self-Healing Optoacoustic Patch with High Damage Threshold and Conversion Efficiency for Biomedical Applications.

Compared with traditional piezoelectric ultrasonic devices, optoacoustic devices have unique advantages such as a simple preparation process, anti-electromagnetic interference, and wireless long-distance power supply. However, current optoacoustic devices remain limited due to a low damage threshold and energy conversion efficiency, which seriously hinder their widespread applications. In this study, using a self-healing polydimethylsiloxane (PDMS, Fe-Hpdca-PDMS) and carbon nanotube composite, a flexible optoacoustic patch is developed, which possesses the self-healing capability at room temperature, and can even recover from damage induced by cutting or laser irradiation. Moreover, this patch can generate high-intensity ultrasound (> 25MPa) without the focusing structure. The laser damage threshold is greater than 183.44mJcm-2, and the optoacoustic energy conversion efficiency reaches a major achievement at 10.66 × 10-3, compared with other carbon-based nanomaterials and PDMS composites. This patch is also been successfully examined in the application of acoustic flow, thrombolysis, and wireless energy harvesting. All findings in this study provides new insight into designing and fabricating of novel ultrasound devices for biomedical applications.

Aligned, carbon nanofibers containing barium titanate and their polydimethylsiloxane composites for electromagnetic interference shielding

The rapid development of wireless communication technology and miniaturization of electronic devices have escalated the demand for high-performance electromagnetic interference (EMI) shielding materials which are light weight, waterproof, and flexible. Herein, we have demonstrated fabrication of aligned and non-aligned one-dimensional (1-D) N-doped carbon nanofibers (CNF) incorporated with barium titanate (BaTiO3) nanoparticles (NPs) [BaTiO3–CNF] for EMI shielding in X, Ku, and K-band. BaTiO3–CNF was prepared through electrospinning followed by carbonization at 900 °C. The aligned BaTiO3–CNF exhibited better EMI shielding effectiveness (81 dB with a thickness of 0.24 mm) compared to the non-aligned BaTiO3–CNF (59.2 dB). Alignment of N-doped CNF enhanced electronic conduction in axial direction of the fibers and exhibited higher electrical conductivity of 1.4 S cm−1. The alignment also improved multiple internal reflections and interfacial polarization in the layered structure of the CNF. PDMS composites of BaTiO3–CNF were prepared by hand-layup method to make them flexible, and the composites exhibited similar EMI shielding properties as that of BaTiO3–CNF. Alignment of suitably doped CNF may open up new opportunities for industrial-scale production of shielding materials that are waterproof, lightweight, and flexible.

Preparation and microwave absorption properties of flexible composites containing Ag decorated polystyrene powders

Polystyrene (PS) microspheres have the advantages of good stability, corrosion resistance and low density, which have a broad application prospect. In this paper, PS composite microspheres with 20% silver plating content were prepared by chemical plating method and incorporated into polydimethylsiloxane (PDMS) flexible matrix to prepare Ag@PS/PDMS flexible wave-absorbing materials. The electromagnetic parameters were adjusted to optimize the dielectric and wave-absorbing properties by varying the additional amount of Ag@PS composite microspheres in Ag@PS/PDMS composites. The X-ray diffraction (XRD) results proved the successful preparation of Ag@PS composite microspheres. The SEM and EDS images indicated that the Ag particles were attached to the external surface of PS. The presence of Ag particles in the Ag@PS composite microspheres enhances their electrical conductivity and enables the formation of a conductive network. This, in turn, improves the composites’ dielectric constant. The optimal wave-absorbing capability of the composites was achieved when the Ag@PS composite microspheres were added at a weight percentage of 50%. When the sample attains a thickness of 1.8[Formula: see text]mm, a reflection loss of at least −39.8[Formula: see text]dB is attained at 10.4[Formula: see text]GHz, along with a bandwidth of 1.6[Formula: see text]GHz (9.1–10.7[Formula: see text]GHz) for the effective absorption bandwidth (EAB). The pressure-sensitive properties of the pliable composites were investigated as well. The optimal pressure-sensitive performance of Ag@PS/PDMS composites was achieved with a 60[Formula: see text]wt.% addition of Ag@PS composite microspheres. The resistance undergoes significant changes when subjected to pressure with a sensitivity of 9.7. The results indicate that the flexible composites’ wave-absorption and pressure-sensitivity properties can be modulated by adjusting the amount of Ag@PS composite microspheres added.

Wide-range soft anisotropic thermistor with a direct wireless radio frequency interface

Temperature sensors are one of the most fundamental sensors and are found in industrial, environmental, and biomedical applications. The traditional approach of reading the resistive response of Positive Temperature Coefficient thermistors at DC hindered their adoption as wide-range temperature sensors. Here, we present a large-area thermistor, based on a flexible and stretchable short carbon fibre incorporated Polydimethylsiloxane composite, enabled by a radio frequency sensing interface. The radio frequency readout overcomes the decades-old sensing range limit of thermistors. The composite exhibits a resistance sensitivity over 1000 °C−1, while maintaining stability against bending (20,000 cycles) and stretching (1000 cycles). Leveraging its large-area processing, the anisotropic composite is used as a substrate for sub-6 GHz radio frequency components, where the thermistor-based microwave resonators achieve a wide temperature sensing range (30 to 205 °C) compared to reported flexible temperature sensors, and high sensitivity (3.2 MHz/°C) compared to radio frequency temperature sensors. Wireless sensing is demonstrated using a microstrip patch antenna based on a thermistor substrate, and a battery-less radio frequency identification tag. This radio frequency-based sensor readout technique could enable functional materials to be directly integrated in wireless sensing applications.

GMP/Al2O3/ZnO/PDMS thermal interface materials with anisotropic thermal conductivity and electrical insulation ability obtained by 3D‐printing method

AbstractDue to the continuous increase in power density and power consumption, thermal management has become a crucial issue in electronic devices like integrated circuits. Polymer‐based thermal conductive composites possess excellent thermal and mechanical properties, making them ideal materials for thermal management in the modern microelectronic industry. In this work, we present a combination of filler hybridization strategy and 3D‐printing technology to synergistically enhance the thermal conductivity of graphite microplatelets (GMP)/alumina (Al2O3)/zinc oxide (ZnO)/polydimethylsiloxane (PDMS) composite (o‐GAZP). When the content of GMP reaches 4.5 vol%, the 3D‐printed composite material exhibits a directional thermal conductivity of up to 4.51 W m−1 K−1. This value is significantly higher than the thermal conductivity of a randomly mixed GMP/Al2O3/ZnO/PDMS composite (1.98 W m−1 K−1). The remarkable thermal conductivity can be attributed to the anisotropic structural design, which benefits from the orientation of GMP and the creation of a multi‐scale dense structure through filler compounding. Additionally, the presence of Al2O3 and ZnO effectively separates the GMP particles, preventing the formation of electron transfer pathways and improving the electrical insulation performance of the composites. Furthermore, the impact of the anisotropic structural design on the thermal conductivity of the composites was verified through finite element simulation. This study demonstrates that constructing efficient thermally conductive and electrically insulating pathways by densely packing highly oriented two‐dimensional anisotropic graphite‐based fillers with uniformly dispersed thermally conductive and electrically insulating fillers is a simple and effective method to enhance the composites' thermal conductivity, electrical resistivity, and mechanical properties simultaneously. These findings hold great potential for various scalable thermal‐related applications. By implementing this approach, composites can exhibit excellent thermal conductivity, high electrical resistivity, and superior mechanical performance.

Enhanced thermal conductivity of electrically insulating polydimethylsiloxane composites with boron nitride nanosheet and aluminum oxide for thermal management on flexible electronics

AbstractWith the trend of integration and miniaturization of stretchable electronics, thermal management has been a crucial issue. Developing novel materials with high thermal conductivity (TC) and flexibility is urgent. Herein, we report a stretchable polydimethylsiloxane (PDMS)/boron nitride nanosheet (BNNS)@spherical aluminum oxide (Al2O3) composite with high TC and electrical insulation prepared by a two‐step strategy of sucrose‐template and hot‐pressing. An effective foam‐pressing route benefits the composites to form a three‐dimensional thermally conductive networks, improving the in‐plane TC value of the resultant composite to 4.03 W/(mK) at the filler mass fraction of 35.7 wt% and enhancing to 4.66 W/(mK) under 40% stretching ratio. Meanwhile, the composites can be restored to their former state and retain thermally conductive stability with repeated bending and twisting tests. Moreover, the composites were applied in LED with stretching, exhibiting good heat dissipation performance. These results demonstrate this PDMS composite can be potentially utilized as a high‐performance material to solve thermal management problems in flexible electronics.Highlights The heat conduction network is prepared by sucrose‐template and hot‐pressing. BNNS@P‐Al2O3 fillers are self‐assembled via the electrostatic interaction. The composites exhibit good thermal conduction and superior flexibility. The thermal conductivity of the composite increases after stretching. The composites can retain thermal conductive stability after deformation.

Enhancing Thermal Conductivity, Electrical Insulation, and Mechanical Strength of Polydimethylsiloxane Composites with Sandwich Structure

In this article, boron nitride (BN)/carbon nanotube (CNT)/boron nitride (BN) (BCB) film of sandwich structure is prepared by vacuum‐assisted filtration. Compared with the thermal conductivity (λ) of BNs–cellulose nanocrystals (CNCs) (BC) film, the λ of sandwich structured BCB films with the same thickness (The preparation process consists of one layer of BC and one layer of CNTs–CNCs (CC) until the completion of three layers of filtration) has been significantly improved. Then, the polydimethylsiloxane (PDMS) matrix is infiltrated into the BCB films by the ultrasonic‐assisted forced infiltration method. Prepared BN/CNT/BN/PDMS (BCBP) composites with sandwich structure have excellent λ and mechanical performance. When the weight ratio of BNs to CNCs is 20:1, the λ of BCBP20:1 attains 5.253 W (m K)−1, compared with other thermally conductive composites with the same thickness (0.1 mm), it has an obvious increase. Besides, the dielectric properties and mechanical flexibility of BCBP are also systematically analyzed. This sandwich structure is prepared in such a method that the BCBP will not cause short circuits in electronic devices under high temperatures while having high λ.