Conductive Polymer Composites Research Articles

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.

The impact of polypyrrole:carboxymethyl cellulose composite nanostructure on conductivity and capacitance

Polypyrrole is a popular conjugated polymer that becomes highly conductive in its p-doped state. The intrinsically non-polar nature of the conjugated bond network limits the processing options of such polymers. Surfactants and polyanions help increase dispersity of conductive polymer in suitable solvents for processing. However, while such dispersions can be highly stable, they are formed by complex nanostructures that significantly impact the conducting polymer composite’s bulk properties. Similarly, complex nanostructures can be formed when surfactants or polyelectrolytes serve as templates during the polymerization of the conducting polymer precursor. Following the report of polypyrrole:carboxymethyl cellulose composites in battery electrodes as conductive binders, we are here investigating the role that nanostructure control can have in optimizing their performance. Using methyl orange as a structural template, we can control the composite’s nanoscopic shape between nanospheres and nanofibers. In the bulk material, the latter gives rise to significantly increased electronic conductivity and capacitance in battery use conditions, underlining the opportunities for improved performance of conducting polymer composites by controlling synthesis conditions.

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.

Review on Conductive Polymer Composites for Supercapacitor Applications

The rising demand for energy storage systems with high power density, rapid charge/discharge capabilities, and long cycle life has pushed extensive research into advanced materials for supercapacitor applications. There are several materials under investigation, and among these materials, conductive polymer composites have emerged as promising candidates due to their unique combination of electrical conductivity, flexibility, and facile synthesis. This review provides a comprehensive analysis of recent advancements in the development and application of conductive polymer composites for supercapacitor applications. The review begins with an overview of the fundamental principles governing electrical conductivity mechanism, applications of conductive polymers and the specific requirements for materials employed for these devices. Subsequently, it delves into the properties of conductive polymers and the challenges associated with their implementation for supercapacitors, highlighting the limitations of pristine conductive polymers and the strategies employed to overcome these drawbacks through composite formation. In this review, conductive polymer composites and their applications on supercapacitors are explored, and their advantages and disadvantages are discussed. Finally, the electromechanical properties of each conductive polymer composite are elaborated.

Improving resistance–strain effects of conductive polymer composites modified by multiscale fillers: Short carbon fiber and carbon nanotube

AbstractConductive polymer composites (CPCs) have attracted much attention in strain sensing applications due to their excellent conductivities and high sensitivities. However, research on simultaneous modification of CPCs with multiple conductive fillers is lacking. This study aims to systematically investigate the electrical conductivities and strain‐sensing properties of two filler‐modified epoxy resin (EP) composites with different scale additives—short carbon fibers (SCFs) and carbon nanotubes (CNTs)—obtained by mixing and curing to obtain the samples. Both the SCF/EP and SCF/CNT/EP composite resistivities decreased with increasing filler content, and 1.35 wt% was the percolation threshold for SCF/EP composites; during monotonic tensile loading, the resistance change ratio (ΔR/R0) of the CPCs increased with increasing strain, and the sensitivities decreased with increasing conductive filler content. The CPCs containing SCFs and CNTs exhibited stable and repeatable resistance responses during cyclic tensile loading, among which the SCF/CNT_1.5/0.3 composite was the most suitable for use as a sensing material with a sensitivity of 0.149. According to the conductivity and resistance–strain response mechanism analysis, the CNTs supplementing and refining the CPC conductive network composed of SCFs were considered the main reason for the resistance response linearization and excellent dynamic response repeatability. CPCs can be widely used in strain sensing and damage monitoring.Highlights Provided a strategy for multiscale conductive filler‐modified epoxy resins. Realized monotonicity of resistance–strain response by adding multiscale conductive fillers. Explored resistance‐strain effect under dynamic cycling loading. Identified optimal materials for damage detection. Analyzed the resistance–strain response mechanism of single and multiscale conductive filler‐modified CPCs.

Fluid-assisted fused deposition modeling 3D printing of anisotropically thermally conductive polymer composites with precisely tunable heat transfer pathways

A fluid-assisted fused deposition modeling (FA-FDM) 3D printing technique was proposed and employed to create anisotropically thermally conductive polymer composites (aniso-TCPCs). These composites have precisely controllable heat conduction pathways achieved by spraying boron nitride (BN) on both sides of the FDM 3D printed POE/PP materials. At the same BN content (cBN), the thermal conductivity (λ) of the aniso-TCPCs is higher than that of the isotropic composites. When cBN = 60 wt%, the λ of the aniso-TCPCs could reach 1.43 W m−1 K−1, improved over 510 % as compared to the POE/PP matrix. Both experimental and simulation results show that the design of the anisotropically thermally conductive pathways can significantly improve the thermal conductivity of the polymer composites for efficient heat dispersion. Overall, the present study would provide a point of reference for the rational design of effective heat dissipation materials with highly and precisely tunable heat transfer pathways.

Controlled Synthesis of Polyaniline-Based Nanomaterials with Self-Assembly and Interface Manipulation.

Versatile nanostructures of conducting polymers are highly relevant based on unique properties, including electrical, optical, and thermal, with changes in morphology. This contribution reports a facile and reproducible synthesis approach for the design of conducting polymer nanostructures from zero- to three-dimensional composites. Two polymerization steps, namely, self-assembly-directed and interface thin layer-templated polymerizations in this synthesis, were kinetically controlled to fabricate such nanostructures directly. The uniquely designed bicontinuous nanoreactor offers an easy synthesis technique for fabricating 3D multifunctional conducting polymer composites. Self-assembly-directed polymerization could be controlled to form nanorods and further directed to form nanobowl/hollow spherical structures. The interface thin layer template process was tuned to produce hollow spherical and 2D film nanostructures. Kinetic control of polymerization was able to provide access to unprecedented nanostructures of the conducting polymers ranging from DNA origami to gecko-inspired nanostructures, with potential applications in drug delivery, energy storage, and adhesive materials. For example, this is the first conducting polymer material that can demonstrate similar adhesiveness (around 8 N/cm2) to gecko finger hairs.

Design, Processing, and Challenges of Multicomponent Polymer Composites for Improved Electromagnetic Interference Shielding Properties: A Review

AbstractThe colossal development of modern electronic devices has inevitably led to an increase in electromagnetic interference (EMI), which has gradually become the fourth most prevalent type of pollution in the world. It is therefore necessary to seek more effective EMI‐shielding materials to overcome the shortcomings of conventional metal‐based materials, which include high density, a lack of mechanical flexibility, low corrosion resistance and costly processing. Conductive polymer composites (CPCs) have attracted more and more attention due to their superiority in many aspects. However, their performances should be further enhanced for future applications. One polymer with only one type of filler often cannot meet this kind of requirement. In this paper, filled polymer materials for EMI shielding are reviewed in terms of their processing, rheological properties, conductivity, and shielding effectiveness. Moreover, the combination of different ingredients and fillers when fabricating multicomponent composites for EMI shielding is also highlighted. The coordination of various components in composites with different structures, including solid, segregated, layered/sandwiched, and foamed/porous structures, is then discussed.

Achieving low dielectric constant and high thermal conductivity polymer composites by using larger POSS functionalized boron nitride nanosheets

A series of larger POSS-functionalized boron nitride nanosheets were prepared and utilized to address the trade-off between low dielectric constants and high thermal conductivity in polymer composites.

Numerical modeling of the effects of the shape and aspect ratio of 3D curved fiber on the percolation threshold and electrical conductivity of conductive polymer composites.

For designing conductive polymer composites (CPCs), understanding how the fiber curvature affects the percolation behavior of curved conductive fibers is essential for determining the effective electrical conductivity σeff of the CPCs. In this work, CPCs were considered as a polymer matrix filled with the random packing of overlapped curved spherocylinders. The geometries of the curved spherocylinders were defined, and inter-curved spherocylinder contact-detecting and system-spanning fiber cluster searching algorithms were developed. The finite-size-scaling method was used to explore how the aspect ratio α and bending central angle θ of a curved spherocylinder affect the percolation threshold ϕc of an overlapped curved spherocylinder system in 3D space. The findings suggest that ϕc decreases as α increases and increases initially before declining as θ increases. An empirical approximation formula was proposed to quantify the effect of the curved spherocylinder's morphology, characterized by the dimensionless excluded volume Vdex of the curved spherocylinder, on ϕc. The new rigorous bound for ϕc of the soft-curved spherocylinder system was further proposed. A random resistor network model was constructed, and the reliability of this model was validated by comparing the simulations and published data. Finally, a fitting formula was developed to assess the impacts of the normalized reduced density (η - ηc)/ηc and Vdex on the σeff of CPCs. A distinct linear correlation between σeff and (η - ηc)/ηc was constructed, denoted as σeff ∼ [(η - ηc)/ηc]t(α,θ). An empirical approximation model was proposed to establish the relationship between the fiber shape and conductivity exponent t. Our study may provide a theoretical hint for the design of CPCs.

Electrically conductive polymer composites: Today’s most versatile materials?

Electrically conductive polymer composites: Today’s most versatile materials?

Development of A Resistive Sensor Array Based on Graphene and Conducting Polymer Composites for Coffee Aroma Classification

This work aims to create a resistive sensor array for categorizing coffee from various plantations. A mixture of graphene oxide and a conductive polymer is used to create the sensor array. Eight types of sensors were made by dripping various mixtures of graphene oxide, polypyrrole, polyaniline, and poly acetate materials on the interdigitated electrode. Coffee fragrance gas was used for the sensor array test. The surface of the sensor array receives the scent gas created by the brewing of coffee grinds. Each sensor’s response profile is recorded. Each coffee sample has a distinct sensor response profile for simple separation with a distinct pattern. PCA analysis was used to examine sensor responses in order to find classification patterns of coffee samples from diverse plantations that were separated by brewing category. Sensor response data underwent PCA analysis, yielding scores of 54.74% PC1 and 26.17% PC2. These findings suggest that graphene-based and conducting polymer sensor array have a good potential for quick differentiation of different coffee varieties.

Fabrication and evaluation of a flexible antenna device composed of a compatible iron-oxide clay in a PDMS graphene matrix

We create a flexible and robust conductive polymer composite based on iron oxide and a thin film of clay doped with graphene nanoparticles, and test its application as a wearable device for underground workers.

Bilayer-structured carbon nanotube/ethylene–vinyl acetate flexible strain sensors with enhanced sensing performance prepared by biaxial stretching

Conductive polymer composites (CPCs) consisting of polymer materials and conductive nanofillers have excellent flexibility, ease of processing, as well as excellent mechanical and electrical properties, resulting in an enormous application potential in flexible strain sensors and other fields. In this paper, a flexible strain sensor consisting of an ethylene–vinyl acetate (EVA) copolymer/carbon nanotube (CNT) CPC with a bilayer structure was prepared by biaxial stretching. The results indicated that the conductivity of the composites gradually decreased as the stretching ratio (SR) increased, due to the major destruction to the conductive network caused by biaxial stretching. Biaxial deformation facilitates the dispersion and in-plane alignment of CNTs, thereby enhancing the property of the sensor. Compared with the unstretched CNT/EVA-EVA-1.0 bilayer-structured sensor [gauge factor (GF) = 89.4, monitoring range 0.5–50%], the CNT/EVA-EVA-1.5 bilayer-structured sensor (SR = 1.5) after biaxially stretched exhibited higher sensitivity (GF = 349698.2) and a wider strain monitoring range (0.5–120%). In addition, compared with monolayer CNT/EVA sensors, the bilayer-structured sensors exhibited higher stability, highlighting their good application prospects in health monitoring in the field of artificial intelligence.

Enhance thermal conductivity via constructing a low heat resistance interface with quaternized graphene

Interfacial thermal resistance of fillers in thermal conductive polymer composites is a barrier restricting heat dissipation function. In-situ graft of quaternary ammonium group on the surface of graphene can form cation-π interaction, providing a medium for heat transfer between graphene layers. Accordingly, we fabricate polyvinyl alcohol (PVA)-based heat conductive composite containing quaternized graphene stacking structure. With the assistance of non-covalent bonding, the in-plane thermal conductivity of the composite formed by self-precipitation method reaches 9.97 W m−1 K−1 at a filling content of 30 vol%. Molecular dynamics (MD) simulation further explores the promoting effect of the interfacial structure constructed between the charged group and graphene on the interfacial heat transfer. The optimized interfacial structure not only alleviates the bottleneck of interface thermal resistance but also enhances the mechanical properties of composite. This strategy provides an ideal solution to preparation of high-performance thermal management materials for electronic equipment.

Controllable exfoliation of hexagonal boron nitride and tailored three‐dimensional network for highly thermally conductive polymer composites

AbstractThermally conductive but electrically insulating composites have become significant components for efficient thermal dissipation in electronic devices due to their miniaturization, integration, and functionalization. Over the past decade, extensive efforts have been dedicated to improving the thermal conductivity of polymer‐based composites through incorporating various thermally conductive fillers. In particular, boron nitride nanosheets (BNNS) with outstanding intrinsic thermal conductivity, electrical insulation, and chemical stability, have sparked intensive interest from researchers. However, BNNS usually suffers from severe aggregation in polymer matrices, leading to high interfacial thermal resistance. Rational construction of three‐dimensional (3D) BNNS continuous networks is crucial for efficient thermal transport and has also been established as a feasible and effective approach to achieve significant enhancement of thermal conductivity for polymer/BNNS composites. In this brief review, we summarized and introduced recent progress on the controllable exfoliation of h‐BN and tailored three‐dimensional networks for highly thermally conductive polymer composites. The fabrication strategies for 3D BNNS networks and the structure–properties relationships of polymer/BNNS composites are highlighted. Finally, the opportunities and challenges for polymer/BNNS composites based on 3D thermally conductive networks are prospected.

Modeling Electrical Conductivity of Injection-Molded Polymer Composite Bipolar Plates

Bipolar plates can be responsible for up to 40% of the total stack cost and 80% of the weight of a polymer electrolyte membrane fuel cell [1]. To reduce these cost and weight limitations, this work explores injection molding of polymer composites. Injection molding is well-suited for mass production and polymeric materials can significantly reduce the weight of traditional metallic bipolar plates. While polymers lack electrical conductivity, fillers can be added to fabricate conductive polymer composites. The main objective of this research is to model and injection mold polymer composites that will meet the United States Department of Energy technical target for bipolar plate electrical conductivity (> 100 S/cm).A fiber contact model was developed to predict electrical conductivity based upon direction in the material, fiber alignment, fiber length and diameter, fiber concentration, and fiber conductivity [2]. Fiber alignment was measured experimentally by imaging cross sections of injection-molded nylon/carbon fiber composites. Imaging was performed on samples with different weight percentages of carbon fiber and from different mold designs to compare how fiber angles change based on mold geometry. To reduce the significant time required to measure fiber angles experimentally, computer recognition and processing of fiber alignment was developed. Nylon composites were injection molded with carbon fiber loadings ranging from 10 to 40 wt%. Modeling predictions show good correlation within 20% of experimental conductivity measurements. Samples with at least 20 wt% carbon fiber exceeded the US DOE technical target for bipolar plate conductivity, reaching 250 S/cm. In addition to modeling electrical conductivity, the Halpin-Tsai equations are used to model the elastic modulus and ultimate strain of the polymer composite. Tensile testing showed that the modulus of elasticity increases with carbon fiber loadings up to 30 wt%, reaching 7.3 GPa. At loadings above 30 wt%, the higher filler content can create voids which decrease the modulus of elasticity. De Las Heras, A.; Vivas, F. J.; Segura, F.; Andujar, J. M., From the cell to the stack. A chronological walk through the techniques to manufacture the PEFCs core. Renewable & Sustainable Energy Reviews 2018, 96, 29-45.Weber, M.; Kamal, M. R., Estimation of the volume resistivity of electrically conductive composites. Polymer Composites 1997, 18 (6), 711-725. Figure 1

(Invited) Improving Our Understanding of Conducting Polymer Binders

As lithium-ion batteries reach their intrinsic performance limits, next-generation battery technology arises that relies much more strongly on the electrode matrix. Traditional compositions of binders and conductive additives with non-polar surfaces face intrinsic obstacles in these developments. In many next-generation electrode formulations, this incompatibility reveals itself through particle disconnection, increased electrode inhomogeneity1, and conductive additive agglomeration2. Conducting polymers are an apparent solution to such problems. Conducting polymers and their composites can be designed to exhibit increased adhesion, stronger interactions with active material surfaces and electrolytes, and favorable mechanical properties, while providing electronic connectivity at the adhesive contact with the active material3. Many examples have been presented in the literature that demonstrate improved electrode performance using such composites4–6.A common form of conducting polymer composites combines an intrinsically conductive polymer (e.g. polypyrrole, polythiophene, polyaniline) with a polyelectrolyte (e.g. polacrylate, polystyrene sulfonate, carboxymethyl cellulose). This presentation discusses an exploration of some of the fundamental properties of composites of polypyrrole with carboxymethyl cellulose. The work shows intrinsically favorable properties of the composite for application in batteries7. Among those properties are that it can be easily processed in water and N-methyl-2-pyrrolidone, exhibits better adhesion to the current collector, shows competitive conductivity and distributes evenly across active materials. However, it will also be shown that the native structure of this composite is not ideal for long-range conduction and that improvement can be made to the material’s conductivity and capacitance8.Our work is targeting a more complete understanding of the properties of these composites as they are employed in battery environments. It demonstrates enormous promise for the use of conducting polymers as binders, but also gaps in our understanding of their interactions with electrolytes and active materials that need to be addressed to advance their impact on the development of next-generation batteries.