Conductivity Of Composites Research Articles

Highly Thermally Conductive Aramid Nanofiber Composite Films with Synchronous Visible/Infrared Camouflages and Information Encryption.

The development of highly thermally conductive composites that combine visible light/infrared camouflage and information encryption has been endowed with great significance in facilitating the application of 5G communication technology in military fields. This work uses aramid nanofibers (ANF) as the matrix, hetero-structured silver nanowires@boron nitride nanosheets (AgNWs@BNNS) prepared by in situ growth as fillers, which are combined to fabricate sandwich structured thermally conductive and electrically insulating (BNNS/ANF)-(AgNWs@BNNS)-(BNNS/ANF) (denoted as BAB) composite films by "filtration self-assembly, air spraying, and hot-pressing" method. When the mass ratio of AgNWs@BNNS to BNNS is 1 : 1 and the total mass fraction is 50 wt %, BAB composite film has the maximum in-plane thermal conductivity coefficient (λ∥ of 10.36 W/(m ⋅ K)), excellent electrical insulation (breakdown strength and volume resistivity of 41.5 kV/mm and 1.21×1015 Ω ⋅ cm, respectively) and mechanical properties (tensile strength of 170.9 MPa). 50 wt % BAB composite film could efficiently reduce the equilibrium temperature of the central processing unit (CPU) working at full power, resulting in 7.0 °C lower than that of the CPU solely integrated with ANF directly. In addition, BAB composite film boasts adaptive visible light/infrared dual camouflage properties on cement roads and jungle environments, as well as the function of fast encryption of QR code information within 24 seconds.

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

Enhancing thermal conductivity of spherical boron nitride/silicone rubber composites by matching interfacial modulus

ABSTRACT Lightweight, electrically insulating and high thermally conductive materials are highly desirable in electronic and power systems because they can effectively transfer heat and avoid temperature rise of the equipment and devices, thus guaranteeing normal operation. In this work, silica-coated spherical boron nitride (SiO2@s-BN) was successfully fabricated and prepared as a thermally conductive composite by blending with silicone rubber (SR). Due to the modulus matching, SiO2@BN could decrease the thermal resistance between the SR matrices and the thermally conductive fillers, thus achieving higher thermal conductivity compared with the original BN at the same filler loading. When the SR composite is filled with 40 wt% SiO2@BN, the thermal conductivity can reach 1.2 W m−1 K−1, which is 16.5% higher than that of the 40 wt% s-BN/SR composite. Simultaneously, the 40 wt% SiO2@BN/SR composite material not only exhibits excellent dielectric, thermal, and mechanical properties but also demonstrates outstanding processability, maintaining a low precursor viscosity of only 14.5 Pa·s. Overall, this work provides a novel strategy for developing high thermally conductive SR composites with good processability.

Castor oil‐based polyurethane ternary composites with enhanced thermal conductivity and mechanical properties by using liquid metal as second filler

AbstractWith the miniaturization, high frequency of electronic devices, and low‐carbon and sustainable development, higher requirements are put forward for thermal conductive polyurethane composites in terms of comprehensive performance and renewable raw materials. Herein, choosing bio‐based polyurethane (PU) derived from castor oil as matrix, and liquid metal (LM) and aluminum hydroxide (ATH) as hybrid thermal conductive filler, castor oil‐based PU composites were developed via high‐speed rotation and in‐situ polymerization method. The LM‐ATH hybrid filler displayed a synergistic enhancement effect on the thermal conductivity of composites due to the presence of LM‐bridging significantly improved the effective contact probability between ATH fillers. The thermal conductivity of 50LM‐ATH/PU reached 1.69 Wm−1 K−1, which was 9.9 times and 1.4 times higher than that of pure PU and 50ATH/PU, respectively. Notably, the 50LM‐ATH/PU exhibited outstanding mechanical properties including tensile strength up to 4.0 MPa and adhesion strength up to 7.9 MPa, especially elongation at break up to 120% which was improved by 200% compared with 50ATH/PU (40%). Additionally, the composite possessed excellent electric insulation, thermal stability, and inflaming retarding properties, showing great application potential in the electronic devices field.Highlights Castor oil‐based PU composites with ATH‐LM hybrid filer were developed. LM‐ATH hybrid filler of 2:8 promoted the thermal conductivity of composites. Hybrid filler than ATH‐endowed composites with better mechanical properties. The ATH‐LM/PU exhibited excellent electric insulation.

Study on deterioration of mechanical properties and voltage-strength theoretical model of CFRP/ conductive ECC composites under coupling effect of anode polarization, load and erosion environment

This study aims to systematically investigate the deterioration of tensile properties, voltage variation, and voltage-strength theoretical model of CFRP/ conductive ECC composites under coupling effect of anode polarization, load and erosion environment. The effects of testing parameters including conductive ECC mixture type, electric current density, polarization time, tensile stress value, sulfate soak time, and sulfate attack-wet and dry cycle time were synthetically investigated. The experimental results indicated that the voltage increases approximately linearly with the increase of degradation time in the voltage-deterioration time curves. The stress-strain curve can be divided into three stages: the stress-strain linear increase stage, the strain hardening characteristic stage, and the decline stage during failure. The conductive ECC mixture type, polarization time, current density, tensile stress value, sulfate soak time, and sulfate attack-wet and dry cycle time all have significant effects the deterioration of tensile strength and the voltage change ratio of CFRP/ conductive ECC composite. More importantly, an innovative voltage-strength theoretical model was proposed, which can predict the relationship between voltage and material deterioration strength. The theoretical model is in good agreement not only with the experimental results of this study, but also with the results of other studies. The model proposed can be used to predict deterioration degree of materials in real time, which has very important guiding significance for impressed current cathodic protection-structural strengthening technology (ICCP-SS) technology. This study is expected to promote a more comprehensive understanding of the deterioration of mechanical properties and voltage-strength theoretical model of CFRP/conductive ECC composites for ICCP-SS technology.

Advances in Monte Carlo Method for Simulating the Electrical Percolation Behavior of Conductive Polymer Composites with a Carbon-Based Filling.

Conductive polymer composites (CPCs) filled with carbon-based materials are widely used in the fields of antistatic, electromagnetic interference shielding, and wearable electronic devices. The conductivity of CPCs with a carbon-based filling is reflected by their electrical percolation behavior and is the focus of research in this field. Compared to experimental methods, Monte Carlo simulations can predict the conductivity and analyze the factors affecting the conductivity from a microscopic perspective, which greatly reduces the number of experiments and provides a basis for structural design of conductive polymers. This review focuses on Monte Carlo models of CPCs with a carbon-based filling. First, the theoretical basis of the model's construction is introduced, and a Monte Carlo simulation of the electrical percolation behaviors of spherical-, rod-, disk-, and hybridfilled polymers and the analysis of the factors influencing the electrical percolation behavior from a microscopic point of view are summarized. In addition, the paper summarizes the progress of polymer piezoresistive models and polymer foaming structure models that are more relevant to practical applications; finally, we discuss the shortcomings and future research trends of existing Monte Carlo models of CPCs with carbon-based fillings.

Polypyrrole-wool composite with electrical heating properties fabricated via layer-by-layer method

This study presents the development of conductive polymer-textile composites with outstanding electric heating properties achieved through the in-situ polymerization of polypyrrole on wool-felt fabrics, renowned for their superior thermal insulation. Employing successive layer-by-layer (LBL) cycles facilitated precise control over the uniform deposition of polypyrrole with the fabrics. The investigation focused on the interaction between wool fiber and polypyrrole, evaluating appearance, add-on, and electrical heating performance with varying LBL cycles. The polymerization process resulted in the formation of spherical polypyrrole particles on the wool-felt, with deposition increasing alongside LBL cycle numbers. Mechanical properties, including tensile strength and bending rigidity, exhibited enhancement with polypyrrole deposition, while strain reduction was noted, with minimal influence from LBL cycles. Electrical properties, particularly surface resistance, displayed a rapid decrease up to the second LBL cycle. Concerning electrical heating performance, the application of a 12 V voltage resulted in a linear increase in surface temperature with increasing LBL cycles, peaking at 15.5 ℃. Notably, this sustained electrical heating effect persisted even after voltage removal, attributed to the low thermal conductivity of wool fiber. Moreover, the polypyrrole conductive layer maintained exceptional conductivity following repeated abrasion and washing, credited to improved uniformity through LBL cycles. The synergy of wool's insulating properties and polypyrrole's conductivity, as confirmed in this study, presents the potential for a highly efficient heating fabric. These developed materials exhibited improved heating performance, energy conservation, and minimal change in mechanical properties, making them suitable for applications such as electrical heating smart clothing.

The effect of filler size on the properties of TPU / BN flexible thermal conductive composites prepared by Fused Filament Fabrication

Fused Filament Fabrication (FFF) can promote high aspect-ratio fillers to align in specific direction due to deposition-induced effect, so it is widely used in the preparation of thermal conductive composites. Though many studies about FFF have explored the influence of filler types, content, shape, and orientation on thermal conductivity during FFF, the size effect of filler is neglected. In this work, TPU/BN composites with 30 wt% h-BN were successfully printed by Fused Filament Fabrication. The size effect of h-BN on orientation, morphology, thermal conductivity, and other properties were studied. It is found that large-sized fillers are more prone to orientation and mutual contact during the FFF printing process to form thermal conductive paths. An increase in filler size results in an increase in thermal conductivity along the printing direction, which is up to 2.58 W m−1 K−1. The prepared TPU/BN composite not only has high thermal conductivity but also ensures good flexibility.

Polyurethane composite films with self-assembled graphene fluoride: Constructing conductive pathways for thermal management with electrical insulation

Polymer composites incorporating carbon-based fillers have been demonstrated to have high thermal conductivity (TC), yet their high electrical conductivity restricts their utility in electronic devices. As a solution to this issue, we report graphene fluoride (GF) incorporated thermoplastic polyurethane (TPU) composites that are both thermally conductive and electrically insulating. The TPU composites, engineered for both high TC and electrical insulation while maintaining flexibility, were fabricated using a combination of electrospinning, dip-coating, and hot-pressing techniques. This study aimed to investigate the effects of various dip-coating cycles on the in-plane thermal conductivity (λ∥) of GF@TPU composites. Noticeably, GF@TPU composites exhibited an outstanding TC, reaching up to 13.5 W m−1 K−1 with 10 vol% GF loading, marking a 75-fold increase compared to the neat TPU films. Moreover, the GF@TPU composites exhibited an electrically insulating property of 6.5 × 1010 Ω/m. This work provides a promising strategy to make thermally conductive composites with electrical insulation for thermal management in smart electronics.

Decoupling the Influence of Poly(3,4-Ethylenedioxythiophene)-Collagen Composite Characteristics on Cell Stemness.

Conductive polymers (CPs) are widely studied for their ability to influence a myriad of tissue systems. While their mixed ionic/electronic conductivity is commonly considered the primary driver of these benefits, the mechanisms by which CPs influence cell fate remain unclear. In this study, CP-biomaterial interactions are investigated using collagen, due to its widespread prevalence throughout the body and in tissue engineering constructs. Collagen is functionalized with both electrostatically and covalently bound derivatives of the CP poly(3,4-ethylenedioxythiophene) (PEDOT) doped via backbone-tethered sulfonate groups, which enable high solubility and loading to the collagen biomatrix. Intrinsically doped scaffolds are compared to those incorporated with a commercially available PEDOT formulation, which is complexed with polyanionic polystyrene sulfonate (PSS). Low loadings of intrinsically doped PEDOT do not increase substrate conductivity compared to collagen alone, enabling separate investigation into CP loading and conductivity. Interestingly, higher PEDOT loading bolsters human mesenchymal stromal (hMSC) cell gene expression of Oct-4 and NANOG, which are key transcription factors regulating cell stemness. Conductive collagen composites with commercial PEDOT:PSS do not significantly affect the expression of these transcription factors in hMSCs. Furthermore, it is demonstrated that PEDOT regulates cellular fate independently from physical changes to the material but directly to the loading of the polymer.

Construction of alumina framework with a sponge template toward highly thermally conductive epoxy composites

AbstractCeramic‐based polymer composites are commonly utilized as thermal management materials due to their high thermal conductivity and electrical insulation properties. One efficient method to enhance the thermal conductivity of these composites is by constructing a three‐dimensional thermal conductive network within the polymer matrix. In this study, alumina was coated onto the surface of polyurethane (PU) foam, followed by high‐temperature removal of the PU foam and sintering of the alumina sheets to obtain a continuous alumina framework. Epoxy resin was then infiltrated into this alumina framework to fabricate highly thermally conductive EP/f‐Al2O3 composites. The EP/f‐Al2O3 composite achieved a thermal conductivity of 2.44 W m−1 K−1 when the filler content of 26.8 vol%, representing a 400% improvement compared to EP/Al2O3 composite with randomly dispersed fillers, and a remarkable 1180% enhancement compared to epoxy resin. Infrared thermal imaging also confirmed the excellent heat dissipation capability of the EP/f‐Al2O3 composites. Overall, this research presents an effective method for producing highly thermally conductive and electrically insulating composites that can be used in electronic thermal management applications.Highlights Fabrication of porous Al2O3 frameworks/epoxy composites. Porous Al2O3 frameworks were fabricated by polyurethane foam template. The obtained EP/f‐Al2O3 composite exhibited excellent thermal conductivity.

Construction of micro-nano hybrid structure based on carbon nanotube whisker and alumina for thermally conductive yet electrically insulating silicone rubber composites

High-performance electronics urgently need more effective thermally conductive rubber composites to solve interfacial heat transfer problems in the thermal management systems. Tiny amounts nanocarbon materials (NCM) can significantly improve the thermal conductivity of conventional ceramic-filled rubber composites, but the volume exclusion effect of micrometer ceramic fillers makes NCM highly susceptible to the formation of the conductive pathways, which inevitably leads to the substantial decrease in the volume resistivity of the materials, posing a safety hazard, such as short circuits, to electronic devices. Here, we report an electrostatic self-assembly method to prepare CNW@n-Al2O3 hybrids by loading nano-alumina (n-Al2O3) onto carbon nanotube whiskers (CNW) and co-filling them with micrometer alumina (m-Al2O3) to silicone rubber, constructing a micro-nano-multi-level hybrid network structure, which can fully utilize the high thermal conductivity while shielding the electrical conductivity of CNW. The resulting composite filled with 2 phr of CNW@n-Al2O3 exhibits a significantly enhanced thermal conductivity of 1.137 W/(m·K) and a high volume resistance of 1.323 × 109 Ω cm, and is proved to be used as an excellent thermal interface material to assist the heat dissipation of the microelectronic chip. This study provides a facile and effective strategy for the design of thermally conductive yet electrically insulating rubber composites filled with CNW, which shows a bright application prospect in the thermal management of high-performance electronic devices.

Advances in Liquid Crystal Epoxy: Molecular Structures, Thermal Conductivity, and Promising Applications in Thermal Management

Traditional heat conductive epoxy composites often fall short in meeting the escalating heat dissipation demands of large‐power, high‐frequency, and high‐voltage insulating packaging applications, due to the challenge of achieving high thermal conductivity (k), desirable dielectric performance, and robust thermomechanical properties simultaneously. Liquid crystal epoxy (LCE) emerges as a unique epoxy, exhibiting inherently high k achieved through the self‐assembly of mesogenic units into ordered structures. This characteristic enables liquid crystal epoxy to retain all the beneficial physical properties of pristine epoxy, while demonstrating a prominently enhanced k. As such, liquid crystal epoxy materials represent a promising solution for thermal management, with potential to tackle the critical issues and technical bottlenecks impeding the increasing miniaturization of microelectronic devices and electrical equipment. This article provides a comprehensive review on recent advances in liquid crystal epoxy, emphasizing the correlation between liquid crystal epoxy's microscopic arrangement, organized mesoscopic domain, k, and relevant physical properties. The impacts of LC units and curing agents on the development of ordered structure are discussed, alongside the consequent effects on the k, dielectric, thermal, and other properties. External processing factors such as temperature and pressure and their influence on the formation and organization of structured domains are also evaluated. Finally, potential applications that could benefit from the emergence of liquid crystal epoxy are reviewed.

Effect of soil type on some composition parameters of Vitis vinifera L. cv. Nero d'Avola grapes at different stages of ripening

SummaryIn this study, the soil effect on the chemical composition of red grapes from Vitis vinifera L. (cv Nero d'Avola) was studied. The soil effect was evaluated by considering the main soil chemical–physical parameters (e.g., texture, pH, total carbonates, cation exchange capacity, electric conductivity, organic matter, and mineral composition) of four vineyards located in the southwestern coast of Sicily (southern Italy). Grapes' quality in relation to different soils was investigated by studying some composition parameters and the (in)/homogeneity of ripeness of grapes at the harvest date. Results suggested that the soil greatly affected the quality of Nero d'Avola red grapes. The most impactful soil parameters were cation exchange capacity, electric conductivity, pH, and mineral composition (especially P and Mn content) that are directly involved into grapevine nutrition. Through multivariate statistical analysis, it was highlighted that the soil effect was remarkable within a specific vintage. However, when more vintages are considered simultaneously, the vintage effect (conceivably through the inter‐annual climatic variability) is the major factor determining grapes quality.

Thermal Conductivity Enhancement of Polymeric Composites Using Hexagonal Boron Nitride: Design Strategies and Challenges.

With the integration and miniaturization of chips, there is an increasing demand for improved heat dissipation. However, the low thermal conductivity (TC) of polymers, which are commonly used in chip packaging, has seriously limited the development of chips. To address this limitation, researchers have recently shown considerable interest in incorporating high-TC fillers into polymers to fabricate thermally conductive composites. Hexagonal boron nitride (h-BN) has emerged as a promising filler candidate due to its high-TC and excellent electrical insulation. This review comprehensively outlines the design strategies for using h-BN as a high-TC filler and covers intrinsic TC and morphology effects, functionalization methods, and the construction of three-dimensional (3D) thermal conduction networks. Additionally, it introduces some experimental TC measurement techniques of composites and theoretical computational simulations for composite design. Finally, the review summarizes some effective strategies and possible challenges for the design of h-BN fillers. This review provides researchers in the field of thermally conductive polymeric composites with a comprehensive understanding of thermal conduction and constructive guidance on h-BN design.

Improvement of the Piezoresistive Behavior of Poly (vinylidene fluoride)/Carbon Nanotube Composites by the Addition of Inorganic Semiconductor Nanoparticles.

Conductive polymer composites (CPCs), obtained by incorporating conductive fillers into a polymer matrix, are suitable for producing strain sensors for structural health monitoring (SHM) in infrastructure. Here, the effect of the addition of inorganic semiconductor nanoparticles (INPs) to a poly (vinylidene fluoride) (PVDF) composite filled with multi-walled carbon nanotubes (MWCNTs) on the piezoresistive behavior is investigated. INPs with different morphologies and sizes are synthesized by a hydrothermal method. The added inorganic oxide semiconductors showed two distinct morphologies, including different phases. While particles with flower-like plate morphology contain phases of orth-ZnSnO3 and SnO, the cauliflower-like nanoparticles contain these metal oxides and ZnO. The nanoparticles are characterized by field-emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), and the nanocomposites by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). Cyclic tensile testing is applied to determine the strain-sensing behavior of PVDF/1 wt% MWCNT nanocomposites with 0-10 wt% inorganic nanoparticles. Compared to the PVDF/1 wt% MWCNT nanocomposite, the piezoresistive sensitivity is higher after the addition of both types of nanoparticles and increases with their amount. Thereby, nanoparticles with flower-like plate structures improve strain sensing behavior slightly more than nanoparticles with cauliflower-like structures. The thermogravimetric analysis results showed that the morphology of the semiconductor nanoparticles added to the PVDF/MWCNT matrix influences the changes in thermal properties.

Percolation behavior and sensing performance of polypropylene‐based conductive polymer composites under compressive strains and temperature

AbstractPercolation behavior is highly significant for mechanical, thermal, and electrical properties, as well as manufacturing processes of conductive polymer composites (CPCs). It has been reported that temperature and external loads are important parameters directly affecting the percolation threshold. Herein, carbon black/polypropylene (CB/PP) and carbon black/multiwalled carbon nanotubes/polypropylene (CB/MWCNTs/PP) composites are prepared via the melt blending method. After the synthesis of composites, the rheological properties, the filler distribution, crystallization, and conductive network formation within the composite are evaluated. The effect of conductive network structure on conductive percolation behavior is studied under various compressive strains and temperatures. Finally, the sensing performance under compressive strain and temperature cycling is discussed. Obtained results reveal that MWCNTs work as “bridges” between segregated CB particles leading to a synergic effect on the conducting properties. The volume resistivity of PP‐based CPCs exhibits a critical strain and a positive temperature coefficient (PTC), resulting in altered percolation. PP‐based CPCs with the addition of MWCNTs have greater PTC intensity, demonstrating sensing stability and sensitivity to compressive strain under temperature cycling. This study underscores the essential contribution of MWCNTs in building conductive networks and elucidates the potential application of PP‐based CPCs with superior sensing performance under compressive strain and varying temperatures.

Multifunctional nanocomposites based on a polyamide 6/polyamide 12 blend and multi‐walled carbon nanotubes

AbstractNanocomposites based on an immiscible blend of polyamide 6 (PA6) and polyamide 12 (PA12) 50/50 wt.% with different contents of multi‐walled carbon nanotubes (MWCNTs) were prepared by extrusion followed by compression molding. These materials have been proved to be electrically conductive in previous investigations for the range of filler content assayed. The morphology of the nanocomposites was analyzed using scanning electron microscopy, both on cryo‐fractured and postmortem uniaxial tensile samples. Rheological measurements were performed along with differential scanning calorimetry, to assess the materials microstructure and thermal transitions. Furthermore, uniaxial tensile tests were carried out to determine mechanical properties such as stiffness, strength, and strain at break and to investigate the effect of MWCNTs on these properties. Finally, fracture tests were also conducted to evaluate how incorporating MWCNTs affected nanocomposites toughening capabilities. The obtained results suggest a notable improvement in the mechanical properties in the nanocomposites with low amounts of nanofiller. This expands their potential applications as conductive polymer composites (CPCs) and positions them as promising multifunctional materials.Highlights CPCs based on a PA blend and MWCNTs were successfully obtained. CNTs strongly affected the blend morphology and rheological properties. CNTs significantly modified the crystallization behavior of PA6. Ductility greatly improved at low CNT contents but decreased at high loadings. Stiffness increased steadily with increasing CNT content.

Effects of Fabrication Process of Conductive TPU Composites on Dual-Function Gas Sensor and Energy Devices

Effects of Fabrication Process of Conductive TPU Composites on Dual-Function Gas Sensor and Energy Devices

Crystallization induced segregated structure for outstanding conductive property with low percolation threshold

Conductive polymer composites (CPCs) are promising alternatives to metal conductive materials due to their light-weight and low-cost. This work investigates the effect of the crystallization behavior of the matrix on the electrical property of CPCs, where semi-crystalline polypropylene (PP) and amorphous styrene-butadiene-styrene tri-block copolymer (SBS) are selected as a matrix, respectively, and conductive carbon black (CB) particles are introduced into matrixes by melting blending. Based on the electrical properties of CPCs with various CB contents and percolation theory, the percolation threshold of 1.8 vol% in PP matrix composites is obtained, much lower than that of SBS matrix composites (5.4 vol%). The analysis with a polarizing microscope and differential scanning calorimeter confirms that such a significant difference in percolation threshold between two composites is due to the crystallization behavior while the crystallization induced segregated structure is proposed. Finally, the rheology behaviors and mechanical properties are characterized for microstructures and applications, respectively.