Binary Filler Research Articles

Synergistic enrichment of electrically conductive polypropylene‐graphite composites for fuel cell bipolar plates

In this research study, electrically conductive Polypropylene (PP) based composites were developed using twin-screw extrusion technique with the objective of investigating the effects of primary and binary fillers on the overall electrical performance of the composites with relation to their mechanical properties. Thermoplastic polymers are suitable for a wide variety of applications due to their inherent characteristics, such as low density, ease of processibility, and recyclability. The addition of conductive fillers to thermoplastic resins reduces the material's resistivity and provides the ability to conduct heat and electricity, making them an excellent candidate for the manufacturing of fuel cell bipolar plates. The first part of this research study consists of studying the effect of graphite content on the electrical and mechanical properties of PP composites, whereas the second part focuses on the analysis of the effects of a multi-filler composite system consisting of Multi-Walled Carbon Nanotubes (MWCNT) and Carbon Black (CB) in the graphite-PP composites. The experimental results revealed that the maximum electrical conductivity obtained from the binary filler composites is up to 127% higher compared to that of the single filler composites. The addition of binary fillers also improved the flexural strength of the composites. This experimental study constitutes new prospects in the development of electrically conductive thermoplastic composites with sound mechanical properties for fuel cell bipolar plates.

The Impact of Cement Kiln Dust and Cement on Cold Mix Asphalt Characteristics at Different Climate

Cold bitumen emulsion mixtures (CBEMs) are made up of the same materials that are used in hot mixes. However, asphalt emulsion and water are used in such mixes. To date, many countries are still not using these mixes as a structure layer. This can be attributed mainly to their low resistance to rainfall, long curing time and low early strength. The addition of cementitious filler to CBEMs as a clean paving material is a potential technique to achieve superior mechanical qualities. The aim of this research is to compare improved CBEMs that might be used as a wearing surface to hot mix asphalt (HMA). These improvements were carried out through the use of a combination of cement and limestone, or a combination of ordinary Portland cement (OPC) and cement kiln dust (CKD). CBEMs were prepared according to Egyptian and British gradations using different percentages of ordinary Portland cement (OPC), CKD, and limestone. This may offer a new cold bitumen emulsion mixture to be used as a structural pavement layer in such countries. The main tests performed for the assessment of the mixes in this research are indirect tensile stiffness modulus, fatigue resistance, and resistance to rutting at different temperatures (20 °C, 45 °C, and 60 °C). The results show that adding OPC to CBEMs enhanced the results in terms of ITSM, rutting and fatigue resistance. However, significant improvements were made by binary filler made of CKD and OPC to the said mechanical properties in terms of both UK and Egyptian gradations. The ITSM values for both CBEMUK6 and CBEMEg6, which contain 80% OPC + 20% CKD, improved by around 8 and 9 times in comparison to CBEMUK1 and CBEMEg1, which contain 20% OPC + 80% L.S, respectively.

Highly thermoconductive yet ultraflexible polymer composites with superior mechanical properties and autonomous self-healing functionality via a binary filler strategy.

It is still a formidable challenge to develop ideal thermal dissipation materials with simultaneous high thermal conductivity, excellent mechanical softness and toughness, and spontaneous self-healing. Herein, we report the introduction of sandwich-like boron nitride nanosheets-liquid metal binary fillers into an artificial poly(urea-urethane) elastomer to address the above issue, which confers the composite elastomer with a unique thermal-mechanical-healing combination, including a low modulus, high in-plane thermal conductivity and high mass loading of rigid fillers but self-recoverability and room-temperature self-healing.

Recent Progress in Mixed-Matrix Membranes for Hydrogen Separation.

Membrane separation is a compelling technology for hydrogen separation. Among the different types of membranes used to date, the mixed-matrix membranes (MMMs) are one of the most widely used approaches for enhancing separation performances and surpassing the Robeson upper bound limits for polymeric membranes. In this review, we focus on the recent progress in MMMs for hydrogen separation. The discussion first starts with a background introduction of the current hydrogen generation technologies, followed by a comparison between the membrane technology and other hydrogen purification technologies. Thereafter, state-of-the-art MMMs, comprising emerging filler materials that include zeolites, metal-organic frameworks, covalent organic frameworks, and graphene-based materials, are highlighted. The binary filler strategy, which uses two filler materials to create synergistic enhancements in MMMs, is also described. A critical evaluation on the performances of the MMMs is then considered in context, before we conclude with our perspectives on how MMMs for hydrogen separation can advance moving forward.

Synergistic effect of talc/calcined kaolin binary fillers on rigid PVC: Improved properties of PVC composites

AbstractThis study aims to develop poly(vinyl chloride) (PVC) composites prepared by melt mixing by using a combination of talc and calcined kaolin as filler in order to improve the disadvantages of rigid PVC, which is widely used in industry, such as poor mechanical properties and low thermal stability. In addition, PVC/talc and PVC/calcined kaolin composites were also examined for comparison. The calcined kaolin is modified with urea to increase the surface area (chemical treatment), while the surface of both fillers is coated with stearic acid for good compatibility with PVC (mechanical treatment). Scanning electron microscopy micrographs showed homogeneous distribution of mechanically processed fillers. Attenuated total reflectance–Fourier‐transform infrared spectroscopy analysis revealed successful coating of the fillers with stearic acid. Also, new bands were detected in the spectrum of urea‐treated calcined kaolin, showing an effective chemical treatment. It has been observed that the treatment of fillers improves the mechanical properties of PVC. Thermogravimetric results showed that delaminated calcined kaolin increased the thermal stability of PVC composites. The results of this study proved that binary filler composites combine good properties of both (synergistic effect) and good filler dispersion can be obtained by using stearic acid and urea.

Analysis of effect of modification of silica and carbon black co-filled rubber composite on mechanical properties

Abstract Silica and carbon black (CB) co-filled rubber composite was widely used for tire tread and other rubber products because of combined advantages of binary fillers, such as low hysteresis, good abrasion resistance, and reinforcement. Numerous studies have been focused on the filler–rubber interaction with the aim of obtaining optimum performances. To investigate the effect of modification on properties of rubber composite, modified silica and CB co-filled rubber composite was prepared with a multi-functional silane coupling agent, 2-aminoethyl-2-(3-triethoxysilylpropyl)aminoethyl disulfide (ATD). Such modification significantly enhanced the filler–rubber interaction and improved the filler dispersion. For the modified composites, the state of cure, hardness, tensile strength before and after aging, stress at 300% elongation, tear strength, abrasion resistance, rebound resilience, compression set, temperature rise, and the value of dynamic loss coefficient ranging from −20°C to 80°C were significantly improved, especially with low ATD dosage (3.0 phr). This modification provides an effective route to prepare silica and CB co-filled rubber composites with improved mechanical properties and dynamic mechanical properties.

Effect of feldspar filler on physical and dynamic properties of SBR/CB based tire tread compounds: Effect of addition method of silane coupling agent

In this work, the effects of using feldspar (FLD) as an alumina-silicate inorganic filler, with carbon black (CB) as a novel binary filler system, on the properties of SBR compounds were investigated for tire applications. The bis(triethoxysilylpropyl) disulfide (TESPD) was used for modification of FLD. The SBR hybrid composites were produced by replacing 10 phr of CB filler with neat FLD and functionalized FLD (F-FLD). The TESPD was added directly to the rubber mixture including neat FLD. The SBR composite which has only CB filler (50CB) was found to have the highest damping parameter (tan δ) value at 60°C. On the other hand, the composites loaded with the CB and the FLD fillers exhibited relatively lower tan δ at the same temperature showing lower rolling resistance meaning better fuel saving performance. The lowest rolling resistance was achieved for the 40CB-10F-FLD most probably due to its stronger interaction with the SBR elastomer molecules through the silane agent-assisted crosslinks of the F-FLD. As another dynamic property, the storage moduli at −20°C were found to be lower for the SBR hybrid composites as compared to that of the 50CB composite, exhibiting enhanced winter traction performance of the composites having FLD filler together with CB. The composites containing only 10 phr of FLD and F-FLD, on the other hand, exhibited very low tensile strength values which are not acceptable for tire tread materials.

Mutual dispersion of graphite–silica binary fillers and its effects on curing, mechanical, and aging properties of natural rubber composites

Rubber composites deliver unsatisfactory mechanical performance if the rubber matrices, such as natural rubber, lack appropriate dispersion of fillers such as silica. This study explored the dispersion and reinforcement performance of binary fillers in natural rubber. Graphite powder was used as a solid lubricating silica filler in the rubber matrix, and shear force was applied using a conventional two-roll mixing mill. The curing, mechanical, and morphological properties were studied to evaluate the mechanism of binary filler dispersion in the rubber matrix. Binary fillers comprising silica and graphite offered better mutual dispersion, which was observed by scanning electron microscopy and mechanical testing and confirmed by atomic force microscopy. Better filler dispersion in natural rubber improved the mechanical and age resistance properties. The modulus at 100% strain and stress at break of unfilled rubber were increased by nearly 110% and 15%, respectively, when 20 phr (per hundred gram of rubber) of binary filler in a 1:1 weight ratio was used, and the composite exhibited better aging resistance and mechanical properties, compared to those of composites with single-filler systems, which may be attributable to the excellent filler dispersion in the rubber matrix.

The effect of nano- and micron-scale filler modified epoxy matrix on glass-fiber reinforced polymer insulator component behavior

Glass-fiber reinforced polymer (GFRP) composite rods with epoxy matrix filled with electrically nonconducting particles find widespread use in high-voltage electrical insulator applications. The service loads require a range of different, minimum material property values, e.g. toughness, tensile, or compressive strength, but also component-specific performance, e.g. pull-out friction of surface crimped metal fittings or electric breakdown strength. The contribution discusses selected examples of the effects of different particle filler types on the properties of filled epoxy resin as well as on the behavior of GFRP rods with such a matrix. In all investigated systems CaCO3 was used as micron-sized filler, complemented by different amounts of either nanosilica or core-shell rubber (binary filler), or by both, nanosilica and core-shell rubber (ternary filler). With ternary filler combinations at a content of 36 wt%, fracture toughness GIC was improved in nanocomposite epoxy plates and in GFRP rods by 60% and 100%, respectively compared to a matrix with 20 wt% CaCO3 (used as reference system). The glass transition temperature Tg for some ternary systems dropped from 160 °C (for neat epoxy), to approximately 140 °C, the maximum allowed drop in Tg in view of requirements from further processing steps of the electrically insulating components. The ternary fillers yield transfer of the improvements of fracture properties from epoxy nanocomposite plates into the GFRP rods beyond that of the system with CaCO3 filler only. Compressive strength of the GFRP rods was improved by about 20% only for the binary nanosilica and CaCO3 filler, and was not significantly enhanced with the ternary systems. That combination, however, did not yield improvements in toughness beyond the CaCO3-filled nanocomposite plates and rods. With the range of filler types and contents investigated here, it was hence not possible to simultaneously optimize both, fracture toughness and compressive strength of the GFRP insulator rods.

Spatial structure and aggregation of carbon allotrope nanofillers in isotactic polypropylene composites studied by small-angle neutron scattering

We study the aggregation of carbon allotrope nanofillers in the matrix of isotactic polypropylene with direct small-angle neutron scattering measurements. With the ATSAS software, we analyzed the data and determined the fractal shape, dimension, and sizes of nanofiller aggregation in the bulk of isotactic polypropylene over the range of the scattering angles. We estimated the volume distributions and aggregation of different types of carbon nanofillers at different concentrations: nanographite, graphene nanoplatelets (GNP), fullerenes, single-walled carbon nanotubes (SWCNT), multi-walled carbon nanotubes (MWCNT) and binary fillers MWCNT/GNP. We reconstructed the shape of nanoscale particles and aggregates of a few nanofillers SWCNT, MWCNT and MWCNT/GNP and found that the systems are polydisperse; nanofillers associate in the volume of isotactic polypropylene as fractal dense aggregates with rugged surface, their sizes exceeding original dimensions of nanofillers several times.

Thermo-conductive phase change materials with binary fillers of core-shell-like distribution

Phase change materials (PCMs), in light of high latent heat and isothermal performances during phase transition, behave huge potential in thermal management, and energy storage/conversion, yet still severely suffered from intrinsic unsatisfied thermal conductivity and inferior shape stability. Regarding to these bottlenecks, different from traditional complicated and energy-consuming methods, a facile strategy through merely physical mixing procedures was proposed for fabrication of PCMs with core-shell-like distribution of binary fillers composed of “core” containing polyethylene glycol (PEG) nanocomposites with graphene nanoplates (GNPs) and “shell” filled with hexagonal boron nitride (h-BN). Therefore, as-prepared composite achieves a thermal conductivity of 3.63 W·m−1 K−1 at GNPs/h-BN loading of 0.625 vol% and 15 vol%, respectively, almost 1.5-fold of that of composite counterpart with random filler distribution. Meanwhile, it also possesses high reserved latent heat and could maintain its original shape even at 90 °C, largely promoting its widespread applications.

Composites based on polypropylene and Georgian minerals

Polymer composites on the basis of secondary polypropylene and high dispersive powders of minerals wide spread in Georgia (andesite, quartz sand and a slam) were obtained and investigated their some physical-mechanical, thermal and hydrophobic properties. It is shown that the ultimate strength, and thermal stability extremely depend on the filler concentration and at definite significant of the concentration have maximums. For the composites with binary fillers (quartz sand/slam, quartz sand/andesite and slam/andesite) revealed synergistic effect of anomaly increasing of the ultimate strength at definite proportion of fillers. It is established that modification of the mineral fillers with tetraethoxisilane enhances technical characteristics of the composites.

Synergistic Superiority of a Silver‐Carbon Black‐Filled Conductive Polymer Composite for Temperature–Pressure Sensing

Flexible conductive polymer composites (CPCs) are creating new opportunities in soft electronics and their applications. Compared with CPCs based on unary filler systems, CPCs with binary fillers have plenty of advantages in mechanical and electrical properties due to the synergistic superiority of fillers. Herein, a new kind of flexible binary fillers CPC composed of nano‐sized carbon black (CB) particles and micro‐sized silver (Ag) platelets uniformly dispersed in polydimethylsiloxane (PDMS) is reported and named Ag‐CB‐PDMS. A synergistic conductive network structure based on observation of scanning electron microscope (SEM) is proposed. The conductivity is approximately 20 times higher than that of unary filler system, with a threefold improvement in its stability. Through the regulation of the filler concentration, the temperature coefficient can be adjusted, and the resistance is insensitive to temperature when silver and carbon black concentrations are 15 and 18 wt%, respectively. Meanwhile, Ag‐CB‐PDMS retains good flexibility and shows excellent piezoresistive characteristics. During compression‐release cycles, Ag‐CB‐PDMS exhibits excellent stability, good repeatability (1000 cycles), and fast response time (52 ms). A temperature–pressure sensor is constructed based on Wheatstone bridge for real‐time monitoring of lithium‐ion batteries (LiBs) to achieve early safety warning.

Thermal Properties of Binary Filler Hybrid Composite with Graphene Oxide and Pyrolyzed Silicon-Coated Boron Nitride.

To improve the thermal conductivity of a composite material, the filler dispersion and the interfacial adhesion between the filler and the matrix are important factors. A number of methods for satisfying these criteria are presented herein. Thus, graphene oxide (GO) is incorporated to enhance the dispersion state of surface-modified boron nitride (BN) by increasing the viscosity of the epoxy matrix and by providing steric hindrance. Meanwhile, polysilazane (PSZ) coating and thermolysis were used to enhance the wettability by providing structural similarity between the coating material and the epoxy matrix. Due to these strategies, the thermal conductivity was improved by 253% compared to that of the neat epoxy at a filler fraction of 40 wt %.

Vulcanizate Structures of SBR Compounds with Silica and Carbon Black Binary Filler Systems at Different Curing Temperatures.

The tire industry has shown an increasing demand for the reduction in rolling resistance. Efforts have been made to improve the viscoelastic properties of tire compounds and reduce the weight of tires through optimization of the vulcanizate structure, which has become extremely complex. In this study, vulcanizates using carbon black and silica as binary fillers were prepared at various curing temperatures. Vulcanizate structures with respect to curing temperature were classified according to the chemical crosslink density by sulfur, carbon black bound rubber (i.e., physical crosslink due to carbon black), and silica-silane–rubber network. All properties exhibited a decreasing trend under the application of high curing temperatures, and the decrease in the crosslink density per unit content of filler with an increase in curing temperature was shown to be greater in carbon black than in silica. Mechanical and viscoelastic properties were also measured to evaluate the impact that the compound variates have on tire tread performance. These results serve as a guideline for determining the content and filler type and for setting the cure condition during the design of actual compound formulations to increase the crosslink density of rubber while retaining the necessary mechanical and viscoelastic properties for practical application.

Thermally conductive 3D binetwork structured aggregated boron nitride/Cu-foam/polymer composites

A 3D filler network structure can significantly improve the thermal conductivity of a composite. In addition, a spherically shaped filler is advantageous for high packing density and filler connectivity compared to other shapes. Here, to achieve a high thermal conductivity, epoxy composites were fabricated using spherically aggregated boron nitride (A-BN) and Cu foam as hybrid fillers. To defoam the composites, A-BN was first incorporated into the matrix with Cu foam by a vacuum impregnation process, followed by a curing process. As the A-BN loading increased up to 25 wt%, the thermal conductivity of the composite also increased due to the formation of a heat path. However, when the filler loading exceeded 25 wt%, the thermal conductivity decreases because of filler aggregation. Thus, the composite containing 25 wt% A-BN exhibited the maximum thermal conductivity (2.017 W/mK), with an enhancement of 940% compared with that without filler. In addition, the incorporation of A-BN is beneficial for increasing the volume resistivity of the composite, allowing its practically insulation (1.21 × 1013 Ω cm). This study shows that the formation of 3D network structures with binary fillers is advantageous for the heat management of electronic devices.

Thermal and dielectric properties of epoxy-based composites filled with flake and whisker type hexagonal boron nitride materials

In this work, the epoxy-based composites filled with 3-Aminopropyltriethoxysilane (KH-550) modified binary filler of hexagonal boron nitride (h-BN) flakes and h-BN whiskers were fabricated, and the thermal and dielectric properties of composites were systematically investigated. Adding h-BN whiskers to the filler could effectively form heat conduction paths and improve the phonon transmission efficiency, thereby improving the thermal conductivity of the composites. According to our results, the thermal conductivity of composite with 27 wt% h-BN flakes and 3 wt% h-BN whiskers reached up to 0.819 W·m−1·K−1, which was 3.9 times that of pure epoxy resin. At the same time, the dielectric loss value and dielectric constant of this composite at 1 MHz were 0.02678 and 4.55, respectively, while pure epoxy resin were 0.03602 and 4.33. In addition, introducing h-BN whiskers into the matrix could effectively improve the thermal stability and heat dissipation performance of composites.

Synergistic combination of carbon-black and graphene for 3D printable stretchable conductors

ABSTRACT Stretchable conductors are important ingredients in the new emerging wearable systems. Here, intrinsically stretchable con­ductors (ISCs) based on carbon nanomaterials with a good balance of properties are prepared through synergistic combination of graphene and carbon black (CB) into the matrices of thermoplastic polyurethane (TPU). The inks are prepared through mixing graphene and CB with adjustable mass ratios in TPU by ball-milling, which can be used for blade-coating or 3D-printing. The ISCs prepared by drying the inks at room temperature afford an initial conductivity of 12.5 S cm-1 with an elongation of 140%, or 62.5 S cm-1 with an elongation of 20%, comparable to the carbon nanotube based ISCs. The whole performance is better than those of composites with only one filler (graphene or CB), suggesting the synergistic effect between graphene and CB. Furthermore, the composites with binary fillers have stable electromechanical properties for 1000 cycles of stretching and releasing.

Polyimide-Based Nanocomposites with Binary CeO2/Nanocarbon Fillers: Conjointly Enhanced Thermal and Mechanical Properties.

To design novel polymer materials with optimal properties relevant to industrial usage, it would seem logical to modify polymers with reportedly good functionality, such as polyimides (PIs). We have created a set of PI-based nanocomposites containing binary blends of CeO2 with carbon nanoparticles (nanocones/discs or nanofibres), to improve a number of functional characteristics of the PIs. The prime novelty of this study is in a search for a synergistic effect amidst the nanofiller moieties regarding the thermal and the mechanical properties of PIs. In this paper, we report on the structure, thermal, and mechanical characteristics of the PI-based nanocomposites with binary fillers. We have found that, with a certain composition, the functional performance of a material can be substantially improved. For example, a PI containing SO2-groups in its macrochains not only had its thermal stability enhanced (by ~20 °C, 10% weight loss up to 533 °C) but also had its stiffness increased by more than 10% (Young’s modulus as high as 2.9–3.0 GPa) in comparison with the matrix PI. In the case of a PI with no sulfonic groups, binary fillers increased stiffness of the polymer above its glass transition temperature, thereby widening its working temperature range. The mechanisms of these phenomena are discussed. Thus, this study could contribute to the design of new composite materials with controllable and improved functionality.

Thermal conductive epoxy adhesive with binary filler system of surface modified hexagonal boron nitride and α-aluminum oxide

In this work, we prepared the epoxy-based adhesives with a binary filler system, which was composed of organosilicon modified hexagonal BN (h-BN) and α-Al2O3. H-BN platelets and α-Al2O3 nanoparticles were decorated by aminopropyltrimethoxysilane (APTMS) and glycidylpropyltrimethoxysilane (GPTMS), respectively, to form covalent links to the filler/polymer matrix interface. The surface chemical composition was investigated by Fourrier transform infrared spectroscopy (FTIR) and thermogravimetry analysis (TGA), which demonstrated that the modifiers were successfully grafted onto the surface of fillers. This modification has been confirmed beneficial to thermal conductivity so that the thermal conductivity of adhesives incorporated with modified binary fillers could reach 0.85 w/m k, which is 10% more than specimen filled with unmodified fillers, because covalent links strengthened the interface and prohibited heat diffusion. Modified Hashin–Shtrikman model was utilized to analyze thermal resistance of the binary filler system, indicating that adhesives filled with modified fillers displayed lower thermal resistance. The enhancement of interface also brought about some other positive effect, especially in the decreasing of dielectric constant ( 1014). Furthermore, the mechanical strength is significantly improved when the modified binary fillers were used.