Primary Filler Research Articles

Effect of silica particle size and coating by natural latex on properties of styrene‐butadiene rubber/carbon black/silica composites

AbstractSilica is a renewable resource that has become the primary filler for the rubber used in eco‐friendly tires. However, silica tends to agglomerate in the rubber matrix, particularly, micro‐ and nano‐scale silica, which limits its application. When ordinary‐particle‐size silica with low cost and high stacking density is modified using appropriate methods, high dispersion in rubber and good performance can be achieved with common processing equipment, which has significant engineering application value. In this study, silica particles with different sizes (nano‐scale, 19 and 45 μm) were treated with a 3‐mercaptopropyltriethoxysilane coupling agent (KH580). Subsequently, the silica with the ordinary particle size of 300 mesh (45 μm) was coated with natural latex (NL), and the mechanical properties of the modified silica‐filled styrene‐butadiene rubber (SBR)/carbon black (CB) compounds were investigated. The results revealed that the mechanical properties of the NL‐coated 45 μm silica‐filled composite improved significantly, particularly, in the area of tear strength and elongation at break, the composite properties were improved by 17.1% and 118.2%, respectively. Excellent performance over composites filled with coupling agent‐treated micron‐ and nanoscale silica. Enhancing the surface modification of silica through latex coating provides a means to improve the efficiency of industrial production and reduce costs.Highlights The low‐fine silica treated with KH580 has good dispersibility. Improved mechanical compatibility of NL‐coated silica with rubber. Improvement in strain performance of composites after NL coated with silica. The effect of silica dispersion on composite properties is greater than the effect of particle size. Industrial silica can be successfully addressed, paving the way for extensive utilization.

Application of low‐molecular‐weight polyethylene glycol‐modified silica in natural rubber composites

AbstractSilica serves as the primary filler in the fabrication of eco‐friendly tires, and achieving an optimal dispersion of polar silica within the natural rubber matrix is crucial for crafting high‐performance rubber composites. In this study, biodegradable surfactants polyethylene glycol (PEG) with molecular weights of 200, 400, and 800 were employed to modify silica. The modified silica was characterized by Fourier‐transform infrared spectroscopy; PEG‐modified silica with different molecular weights was compounded with Si69, a conventional silane coupling agent, in the formulation. This aimed to reduce Si69 dosage and mitigate the emission of volatile organic gases, such as ethanol, generated during the silanization reaction between Si69 and silica. Experimental findings revealed that compared with natural rubber composites containing six parts of Si69, the addition of PEG‐modified silica enhanced filler dispersion in the composite while reducing Si69 dosage by three parts. This led to accelerated vulcanization rates, effectively decreased energy consumption during production, and significantly improved wet slip resistance, while maintaining optimal rolling resistance. Rubber composites prepared with PEG800‐modified silica exhibited a 10% increase in elongation at break, a 12% increase in tensile product coefficient, and a 19% enhancement in wet slip resistance.Highlights Silica is modified by polyethylene glycol with molecular weight of 200, 400, and 800. The amount of silane coupling agent and VOC emissions are reduced. The interfacial bonding between silica and rubber matrix is enhanced. The tensile product coefficient and wet slip resistance are improved by 12% and 19%.

Carbon Xerogel as a Novel Minor Conductive Filler for Carbon‐Polymer Composite Bipolar Plates

The current research explores the potential of carbon xerogel as a conductive filler in bipolar plates. The composites comprise graphite as the primary conductive filler and polypropylene as the binder. Carbon xerogel is introduced as a minor conductive filler, and its performance is compared with commercial carbon black. Both nanocarbons exhibit resemblances in microstructure, texture, and surface carbon chemistry. Through‐plane conductivity measurements reveal enhanced electrical conductivity upon replacing a fraction of graphite with either nanofiller. Cross‐sectional analyses of the plates employing computed tomography based on X‐ray diffraction and phase contrasts indicate that the observed electrical conductivity difference stems from reduced trapped air during production and the distribution of the minor filler particles. Given the similarities between carbon xerogel and the reference nanofiller, this study introduces the innovative concept of employing carbon xerogel as a filler for conductive bipolar plates.

Thermally conductive silver adhesive enhanced by MXene@AgNPs with excellent thermal conductivity for thermal management applications

The Thermal Conductive Silver Adhesive (TCSA) efficiently transfers heat from electronic components to heat dissipation components, preventing overheating and extending device lifespan. Despite the effectiveness of commercial sintered nano TCSA, high production costs necessitate a more affordable, high-performance preparation method. This study presents a strategy for preparing ultra-high thermal conductivity (TC) TCSA using multidimensional thermal conductive fillers and low-temperature sintering of silver nanoparticles (AgNPs). MXene@AgNPs particles are synthesized via in-situ reduction of AgNPs on MXene surfaces. These particles, combined with silver microflakes (AgMFs) as primary fillers and epoxy (EP), undergo low-temperature heat treatment to form the AgMFs-MXene@AgNPs/EP composite. Characterization and computational models show that filler-filler interface thermal resistance (ITRf-f) is critical for TC. Adding MXene alone is insufficient, but using MXene@AgNPs particles as secondary fillers allows AgNPs to interconnect fillers, effectively reducing the ITRf-f. The resulting composite achieves an ultra-high TC of 65.51 Wm−1K−1 with 63 wt% total filler content (60 wt% AgMFs, 3 wt% MXene@AgNPs). This study advances the development of low-cost, high-performance TCSA for thermal management applications.

Study on the influence of carbon nanotube modification on the mechanical and magnetic properties of chloroprene rubber‐based magnetorheological elastomers

AbstractThis study explores the mechanical and magnetic properties of magnetorheological elastomers (MREs) based on chloroprene rubber, enhanced with carbonyl iron powder (CIP) as the primary filler. Carbon black serves as the primary reinforcing filler, with multi‐walled carbon nanotubes (CNTs) used as a secondary filler to strengthen the rubber matrix. The primary objective of this research is to examine the effects of the mixture of iron powder with reinforcing fillers and the interaction of these fillers with the rubber matrix on the mechanical and magnetomechanical performance of MREs. CNTs, tubular nanoscale carbon molecules, significantly enhance the tensile strength and fatigue resistance when combined with the MRE matrix. During mixing, CNTs form a network structure within the MRE matrix, promoting the dissipation of accumulated heat and reducing thermal fatigue loss. The addition of 20 parts of CNTs to the CR matrix significantly improved the tensile mechanical properties, with the 100% set elongation stress increasing by up to 260% and the magnetic responsiveness increasing by 30.6%. The addition of 10 parts of carboxylated CNTs most notably enhanced the magnetorheological effect, increasing the magnetic stress relaxation rate by 78%. These enhanced properties enable MREs to provide better vibration control and comfort in automotive suspension systems, improve energy absorption and damping effects in industrial damping systems, and enhance durability and sealing performance in sealant applications.Highlights Carbonyl iron powder, carbon black, and carbon nanotubes (CNTs) were used as fillers to strengthen the chloroprene (CR) matrix magnetorheological elastomers (MREs). CNTs formed a network structure, promoting the dissipation of accumulated heat and reducing thermal fatigue loss. The tensile mechanical property of MRE with 20 parts of CNTs has been significantly improved, with an increasing magnetic responsiveness of 30.6%. Magnetorheological effect of MRE with 10 parts of CNTs has notably enhanced, with the magnetic stress relaxation rate of 78%.

Synergistic effect on dispersion, thermal conductivity and mechanical performance of pyrene modified boron nitride nanotubes with Al2O3/epoxy composites

Due to the intrinsic attributes of boron nitride nanotubes (BNNT), its assimilation into composite materials displays an immense potential for thermal performance augmentation. However, the presence of Van der Waals forces and hydrophobicity of BNNT causing interfacial incompatibility with the polymeric matrix greatly hinders its practical applications. This instigates a dispersion dilemma and subsequent agglomeration of BNNT in the polymer matrix, which massively hampers the thermal performance of the polymer composites. In this respect, we here present a facile BNNT modification strategy; deposition of amine-attached pyrene (PAA) on the BNNT surface through a mild sonication process. The presence of amine in the pyrene molecules reduces the surface tension of PAA deposited BNNT (BNNT-PAA) allowing it to be readily dispersed in the various solvents even at the high concentrations. BNNT-PAA was added as a co-filler along with a primary filler (Al2O3) in the epoxy resin. The formed epoxy composites presented an improvement of as much as 33.1 % in tensile strain and 175.8 % in tensile stress with the addition of 1wt% of BNNT-PAA, while the thermal conductivity of vertical direction was enhanced as high as 62.3 %, possibly due to the constructed BNNT thermal conducting channels among alumina particles.

Investigation of the performance of dopamine‐modified carbon fiber‐reinforced natural rubber‐based magneto‐rheological elastomers

AbstractFive types of magneto‐rheological elastomers (MREs) based on natural rubber were synthesized by incorporating carbonyl iron particles (CIP) as the primary filler. The objective was to investigate the influence of carbon fiber and magnetic particle content on the mechanical and magneto‐rheological properties of the MREs. Carbon fibers (CF) were further added as secondary reinforcement pre‐modified with polydopamine. The composite's microstructure was examined through scanning electron microscopy (SEM), while the mechanical and magnetodynamic properties were assessed using an electronic universal testing machine and an advanced rotational rheometer. The addition of appropriate amounts of CIP and CF resulted in increased rubber modulus, indicating the formation of a filler‐rubber network and the synergistic effect between carbon fibers as a supporting structure and CIP. Compared to the unfilled MREs, the mechanical and magnetodynamic properties were further improved by adding 2 and 4 wt% CF. These findings demonstrate that employing carbon fibers as reinforcing fillers and incorporating suitable magnetic fillers can enhance the magnetic and mechanical properties of the materials, providing a theoretical basis for the study of MREs' performance.Highlights CF and CIP synergistically enhance the strength of the rubber matrix. The MR effect is gradually enhanced with the increase of CIP content. Modified CF has a promoting effect on the magnetic responsivity. Magnetic responsivity increases with increasing modified CF content. Improved mechanical and magnetodynamic properties of composites.

Preparation of Melamine Formaldehyde Foam and a Melamine-Formaldehyde-Organo-Clay Nanocomposite and Hybrid Composites

Mineral fillers can be added to thermoset polymers to improve thermal conductivity and deformation behavior, shrinkage, impact strength, dimensional stability and molding cycle time. This study aims to prepare various hybrid composites (MFHCs) using melamine formaldehyde foam (MF), a melamine formaldehyde organo-clay nanocomposite (MFNC) and also pumice as primary filler, and gypsum, kaolinite and a hollow glass sphere as secondary filler. It also focuses on the study of some mechanical properties and thermal conductivities, as well as their microscopic and spectroscopic characterization. For this, firstly, organo-clay was prepared with the solution intercalation method using montmorillonite, a cationic surfactant and long-chain hydrocarbon material, and then was produced using a melamine formaldehyde nanocomposite with in situ synthesis using a melamine formaldehyde pre-polymer and organo-clay. Finally, hybrid composites were prepared by blending various minerals and the produced nanocomposite. For morphological and textural characterization, both FTIR spectroscopy and XRD spectra, as well as SEM and HRTEM images of the raw montmorillonite (MMT), organo-montmorillonite (OMMT), pure polymer (MF) and prepared hybrid composites, were used. Spectroscopic and microscopic analyses have shown that materials with different textural arrangements and properties are obtained depending on effective adhesion interactions between polymer–clay nanocomposite particles and filler grains. Mechanical and thermal conductivity test results showed that melamine-formaldehyde-organo-clay nanocomposite foam (MFCNC) exhibited a very good thermal insulation performance despite its weak mechanical strength (λ: 0.0640 W/m K). On the other hand, among hybrid composites, it has been determined that the hybrid composite containing hollow glass beads (MFCPHHC) is a material with superior properties in terms of thermal insulation and mechanical strength (λ: 0.642 W/m K, bulk density: 0.36 g/cm3, bending strength: 228.41 Mpa, modulus of elasticity: 2.22 Mpa and screw holding resistance: 3.59 N/mm2).

Tailoring diamondised nanocarbon-loaded poly(lactic acid) composites for highly electroactive surfaces: extrusion and characterisation of filaments for improved 3D-printed surfaces

A new 3D-printable composite has been developed dedicated to electroanalytical applications. Two types of diamondised nanocarbons - detonation nanodiamonds (DNDs) and boron-doped carbon nanowalls (BCNWs) - were added as fillers in poly(lactic acid) (PLA)-based composites to extrude 3D filaments. Carbon black served as a primary filler to reach high composite conductivity at low diamondised nanocarbon concentrations (0.01 to 0.2 S/cm, depending on the type and amount of filler). The aim was to thoroughly describe and understand the interactions between the composite components and how they affect the rheological, mechanical and thermal properties, and electrochemical characteristics of filaments and material extrusion printouts. The electrocatalytic properties of composite-based electrodes, fabricated with a simple 3D pen, were evaluated using multiple electrochemical techniques (cyclic and differential pulse voltammetry and electrochemical impedance spectroscopy). The results showed that the addition of 5 wt% of any of the diamond-rich nanocarbons fillers significantly enhanced the redox process kinetics, leading to lower redox activation overpotentials compared with carbon black–loaded PLA. The detection of dopamine was successfully achieved through fabricated composite electrodes, exhibiting lower limits of detection (0.12 μM for DND and 0.18 μM for BCNW) compared with the reference CB-PLA electrodes (0.48 μM). The thermogravimetric results demonstrated that both DND and BCNW powders can accelerate thermal degradation. The presence of diamondised nanocarbons, regardless of their type, resulted in a decrease in the decomposition temperature of the composite. The study provides insight into the interactions between composite components and their impact on the electrochemical properties of 3D-printed surfaces, suggesting electroanalytic potential.Graphical abstract

Optimization of Filler Compositions of Electrically Conductive Polypropylene Composites for the Manufacturing of Bipolar Plates.

In this research, polypropylene (PP)-graphite composites were prepared using the melt mixing technique in a twin-screw extruder. Graphite, multi-walled carbon nanotubes (MWCNT), carbon black (CB), and expanded graphite (EG) were added to the PP in binary, ternary, and quaternary formations. The graphite was used as a primary filler, and MWCNT, CB, and EG were added to the PP-graphite composites as secondary fillers at different compositions. The secondary filler compositions were considered the control input factors of the optimization study. A full factorial design of the L-27 Orthogonal Array (OA) was used as a Design of Experiment (DOE). The through-plane electrical conductivity and flexural strength were considered the output responses. The experimental data were interpreted via Analysis of Variance (ANOVA) to evaluate the significance of each secondary filler. Furthermore, statistical modeling was performed using response surface methodology (RSM) to predict the properties of the composites as a function of filler composition. The empirical model for the filler formulation demonstrated an average accuracy of 83.9% and 93.4% for predicting the values of electrical conductivity and flexural strength, respectively. This comprehensive experimental study offers potential guidelines for producing electrically conductive thermoplastic composites for the manufacturing of bipolar fuel cell plates.

Synergistic effects of oriented AlN skeletons and 1D SiC nanowires for enhancing the thermal conductivity of epoxy composites

As electronic devices are moving towards miniaturization and integration, the demand for ceramic/polymer composites with high thermal conductivity (TC) are increasing significantly. Herein, we reported a novel idea for rational design and delicate construction of anisotropic three-dimensional thermally conductive networks via the ice template method, using stearic acid-modified AlN particles (AlNm) as the primary filler and SiC nanowires (SiCNWs) as the secondary. As predicted, the as-prepared epoxy (EP)-based composites achieved a maximum TC of 2.56 W·m−1·K−1 in vertical direction at a filling fraction of 55 vol %, which was 12.8 times higher than that of pure EP. More importantly, the enhancement mechanism of composite TC was further demonstrated by realistic heat transfer process and finite element simulations. Furthermore, the prepared composites also displayed excellent thermal stability, high mechanical strength and good dielectric property, indicating that this strategy provides a promising insight for the design of high-performance thermal interface materials (TIMs).

AGREEMENT BETWEEN FRICTION, ABRASION, AND ROLLING RESISTANCE IN SILICA-FILLED TIRE TREAD COMPOUNDS BY TUNING DEGREE OF SILANIZATION AND LOADING OF CARBON BLACK

ABSTRACT Development of green tires by using silica and silane in tread compounds has emerged as a key technology in the tire industry. One of the most important features of a green tire is its low rolling resistance; however, agreement between other performances of a tire, such as wet grip and wear, along with rolling resistance of tread compounds, is a serious challenge. Properties of tire tread compounds are very sensitive to the silanization of silica and the loading of primary and secondary fillers. This work investigates simultaneous effects of silanization of silica as the primary filler and loading of carbon black as the secondary filler. By performing dynamic-mechanical testing in strain sweep and mechanical testing of tire tread compounds, the degree of silanization of silica and loading of carbon black were tuned to make agreement between friction, abrasion, and rolling resistance of green tire tread compounds. Morphology of the filler, kinetics of vulcanization, and bound rubber content in the tread compounds were used to explain the findings. Other than dynamic-mechanical analyses to predict final performance of tread compounds, direct measurements of friction, abrasion, and rolling resistance of tread compounds showed a 43% increase in the coefficient of friction on wet concrete, a 47% increase in abrasion resistance, and a rolling resistance coefficient of approximately 6.5 by using 10 parts per hundred of rubber (phr) of bis(triethoxysilylpropyl)tetrasulfide and 10 phr of carbon black N330 as the secondary filler.

Electrically conductive composite materials with incorporated waste and secondary raw materials

Silicate composites have very low conductivity in general. It is possible to achieve an electrical resistivity decrease by adding an electro-conductive filler. The conductive mixture consists of cementitious binder, various types of silica sand, and graphite-based conductive fillers. One of the research focusses is partial substitution of ordinary raw materials by alternative components (waste materials by-products and secondary raw materials) and its influence on composite properties. The alternative components studied were fly ash as a partial binder replacement, waste graphite from two different sources and steel shavings as a substitute for conductive filler. Resistivity of cured conductive silicate-based specimens was analysed in relation to changes in physico-mechanical properties in context of microstructural changes in the hardened cementitious matrix (by optical and scanning electron microscopy with energy disperse analysis). Partial substitution of cement by fly ash was found to reduce the electrical resistivity of the composite. Some of the waste graphite fillers significantly reduce the resistivity of the cement composite and increase the compressive strength. It was proven, that is possible to replace primary conductive fillers by secondary raw materials.

An evaluation on mechanical properties of vaccum bagging processed kenaf epoxy nano aluminium oxide and nanographene composites

This paper aims to study the mechanical properties of hybrid polymer composites and the addition of primary and secondary fillers the nano-aluminum oxide and nanographene to the Kenaf epoxy composites. The vacuum bagging method was used to fabricate the composites. The advantage of using vacuum bagging is to reduce blowholes. The weight ratio of Kenaf fiber 50%–60%, matrix 40%, fillers nano-aluminum oxide 0%–6%, and nanographene 0%–3% was considered. Mechanical properties like Tensile strength, Young’s modulus and elongation, flexural strength, flexural modulus, hardness, impact strength, and compression strength were tested.6% nano aluminum oxide and 3% nanographene show a 125% increase in tensile strength, a 45% increase in flexural strength, and almost four times higher flexural modulus recorded. 42% increase in compression strength, and an increase of 40% in impact strength. The highest Vickers hardness is 27. An increase in primary and secondary fillers decreases and a combination of increases the mechanical properties.

Bacterial Contamination Is Involved in the Etiology of Soft-Tissue Filler, Late-Onset, Inflammatory Adverse Events.

The treatment algorithm in late-onset inflammatory adverse events with soft-tissue fillers depends primarily on the assumed causative factor: immunologic or bacterial. The authors included 29 patients, 13 of whom experienced late-onset inflammatory adverse events to fillers (inflammatory group) and 16 who did not (reference group). Biopsies were acquired from both groups with an 18-G needle. Before taking the biopsy, the authors acquired skin swabs for 25 of the 29 patients. The IS-pro method-a new and very sensitive method to detect microbiota-was used. This is a novel broad-range polymerase chain reaction technique based on length and sequence variations of the 16S to 23S ribosomal interspacer region. IS-pro can detect bacteria at low abundances and identify them up to species level. To exclude contamination from skin microbiota, the authors compared the microbiota found on skin swabs with that found in the corresponding biopsies. A high level of Gram-positive bacteria was found in biopsies of soft-tissue fillers, predominantly in patients from the inflammation group. This suggests that these bacteria were introduced during the primary filler injection treatment. The composition of the microbiota on the skin differed markedly from that in the filler, indicating that contamination during the sampling process did not influence results. Bacteria adherent to soft-tissue fillers or bacteremia probably play a causative role in adverse events. Contamination of samples in the biopsies with skin microbiota was excluded. Therapeutic, III.

Physical effects of nanoaluminum oxide and nanographene on kenaf epoxy composite; vacuum bagging process

AbstractIn this study, the effect of secondary filler nanographene and primary filler nanoaluminum oxide with kenaf epoxy was investigated. The vacuum bagging process was performed, and a magnetic stirrer was used for blending additives. Water absorption (borewell, distilled, normal, and seawater) and chemical absorption (acid, base, and neutral solution) tests were carried out to evaluate the water absorption, chemical absorption, thickness swelling, and diffusivity of the composite with varying percentages of fillers. The result demonstrates that the addition of 6% primary and 3% secondary filler together, increases the density of the sample by 13.5% and decreases void content by 77%. The addition of secondary filler lowers water absorption in normal water by 1.3% compared to other types of water, as the addition of secondary filler increases the water absorption decreases by 70% in borewell water, 75% in distilled water, 76% in normal water, and 69% in seawater. Thickness swelling of the samples decreases upon the addition of secondary fillers. In acid, the primary and secondary fillers increase the resistance to dissolution. The diffusivity rate of the sample with a combination of fillers 1.3 × 10−5.

Mechanical and magneto-mechanical properties of styrene-butadiene-rubber-based magnetorheological elastomers conferred by novel filler-polymer interactions

This study was undertaken to explore the mechanical and magneto-mechanical properties of styrene butadiene rubber (SBR) based magnetorhelogical elastomers (MREs) reinforced with carbonyl iron particles (CIP) as a primary filler. Nanocarbon materials such as nano carbon black (NCB) and few layer graphene (FLG) were used as secondary fillers to reinforce the rubber matrix. The key purpose of this study is to demonstration how the mechanical and magneto-mechanical properties of MREs are related with filler-rubber interactions. CIP can reinforce rubber, although it contains micron size particles, and improvements in moduli and fracture toughness values indicate the formation of filler-rubber networks and interactions between the π-electrons of benzene and the d-orbital electrons of iron. Optimization of CIP filler loadings in SBR was performed using mechanical properties. Tensile strength and elongation at break were increased by increasing CIP loadings up to 15 vol%, and the addition of FLG at 2 vol% further improved mechanical and magneto-mechanical properties as compared with 17 vol% CIP in SBR-based MREs. The study shows that the addition of nano reinforcing filler and an optimum amount of magnetic filler enhances magnetic and mechanical properties, which would be useful for high-energy smart damping systems.

Simultaneous determination of additive concentration in rubber using ATR-FTIR spectroscopy

Using attenuated total reflection (ATR) Fourier transform infrared (FTIR) spectroscopy for direct quantitative analysis is highly desirable for many sample systems due to advantages such as rapid spectra collection and being completely non-destructive. However, for many complex sample matrices the feasibility of direct quantitative analysis using ATR-FTIR is uncertain. The commonly used Beer–Lambert law may not be applicable for many systems in general, besides sample related complexities such as inhomogeneity, variable optical properties, or heavily overlapping absorption bands. In this study, we consider fully formulated vulcanized rubber with carbon black or silica as the primary filler as our system of interest. We developed a method to simultaneously quantify the concentration of three different antidegradents of similar chemical structure directly on rubber samples using ATR-FTIR spectra. Results show that absorbance follows the Beer–Lambert law well for the range of antidegradent concentrations considered. Despite this, a direct application of the Beer–Lambert law to deconvolute overlapping peaks between antidegradents proved insufficient. Through the application of partial least squares (PLS) multivariate analysis, remarkable prediction accuracy of within about 0.15 wt% error for all three antidegradents was achieved for both types of rubber formulations, even with high levels of carbon black. These results show the value this method has for quantitative analysis of additives in rubber. Our investigation highlights the potential usefulness of FTIR spectroscopy in general for rapid quantitative analysis directly on samples of interest without any prior chemical separation.

Impacts of filler loading and particle size on the transition to linear-nonlinear dichotomy in the rheological responses of particle-filled polymer solutions

In this study, the nonlinear behavior of carbon black-filled polybutadiene solutions under large-amplitude oscillatory shear is investigated. The results show that in the nonlinear regime, the third harmonic intensity, as measured by the ratio of the third to the first harmonics I3/I1, decreases significantly above a critical concentration ϕc of the polymer in the matrix, which results in the amplitude stress deviating strongly from the linear dependence of strain, while the time dependence of stress remains sinusoidal. Increasing the filler particle size significantly decreases the critical ϕc. However, increasing the filler loading basically has no effect on the transition to linear-nonlinear dichotomy. This transition happens when the mesh size ξ of the entangled polymer network in the matrix becomes smaller than the primary filler particle size. Above ϕc, the topological hindrance of the entangled polymer chains apparently considerably slows down the recovery speed of the broken filler network in the material. Hence, the quasisinusoidal response in the system that has a strain-dependent modulus is probably due to the restoration of the broken filler network requiring longer than the time scale of a typical dynamic perturbation.

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.