Effect of Secondary Carbon Nanofillers on the Electrical,Thermal, and Mechanical Properties of Conductive Hybrid Composites Based on Epoxy Resin and Graphite

In this work, we present a comparative study of the impact of secondary carbon nanofillers on the electrical and thermal conductivity, thermal stability, and mechanical properties of hybrid conductive polymer composites (CPC) based on high loadings of synthetic graphite and epoxy resin. Two different carbon nanofillers were chosen for the investigation—low-cost multi-layered graphene nanoplatelets (GN) and carbon black (CB), which were aimed at improving the overall performance of composites. The samples were obtained by a simple, inexpensive, and effective compression molding technique, and were investigated by the means of, i.a., scanning electron microscopy, Raman spectroscopy, electrical conductivity measurements, laser flash analysis, and thermogravimetry. The tests performed revealed that, due to the exceptional electronic transport properties of GN, its relatively low specific surface area, good aspect ratio, and nanometric sizes of particles, a notable improvement in the overall characteristics of the composites (best results for 4 wt % of GN; σ = 266.7 S cm⁻¹; λ = 40.6 W mK⁻¹; fl. strength = 40.1 MPa). In turn, the addition of CB resulted in a limited improvement in mechanical properties, and a deterioration in electrical and thermal properties, mainly due to the too high specific surface area of this nanofiller. The results obtained were compared with US Department of Energy recommendations regarding properties of materials for bipolar plates in fuel cells. As shown, the materials developed significantly exceed the recommended values of the majority of the most important parameters, indicating high potential application of the composites obtained.     

Effect of Nanofiller on the Mechanical Properties of Carbon Fiber/Epoxy Composites under Different Aging Conditions

In this study, carbon fiber-reinforced epoxy composites (CFRPs) containing multi-walled carbon nanotube (MWCNT) and halloysite nanoclay were fabricated. The effects of these nanofillers (MWCNT and nanoclay) on the tensile and flexural properties of the CFRPs under different aging conditions were studied. These aging conditions included water soaking, acid soaking, alkali soaking, and thermal shock cycling. The experimental results showed that, after accelerated aging, the mechanical performance of the CFRPs decreased. The performance degradation in the soaking environment depends on the immersion temperature and immersion medium. High-temperature accelerated the aging behavior of the CFRPs, resulting in low strength and modulus. The CFRPs were more vulnerable to acid soaking and alkali soaking than water soaking. The MWCNT and halloysite nanoclay are beneficial to improve the immersion aging resistance of the CFRPs, and the additions of nanofillers delayed the performance degradation under immersion aging conditions. However, nanofillers hardly improve the aging resistance of the CFRPs under thermal shock cycling condition. The fracture morphologies were observed by scanning electron microscopy (SEM) to reflect the failure modes of the CFRPs under various aging conditions. Differential scanning calorimeter (DSC) and fourier transform infrared (FTIR) spectroscopy tests were used to estimate the changes in the chemical structures and properties of epoxy resin and its composites under different conditions.     

Tribological Behavior of Carbon-Based Nanomaterial-Reinforced Nickel Metal Matrix Composites

Carbon nanotubes (CNTs) and graphene nanoplatelets (GNPs) with exceptional mechanical, thermal, chemical, and electrical properties are enticing reinforcements for fabricating lightweight, high-strength, and wear-resistant metal matrix composites with superior mechanical and tribological performance. Nickel–carbon nanotube composite (Ni-CNT) and nickel–graphene nanoplatelet composite (Ni-GNP) were fabricated via mechanical milling followed by the spark plasma sintering (SPS) technique. The Ni-CNT/GNP composites with varying reinforcement concentrations (0.5, 2, and 5 wt%) were ball milled for twelve hours to explore the effect of reinforcement concentration and its dispersion in the nickel microstructure. The effect of varying CNT/GNP concentration on the microhardness and the tribological behavior was investigated and compared with SPS processed monolithic nickel. Ball-on-disc tribological tests were performed to determine the effect of different structural morphologies of CNTs and GNPs on the wear performance and coefficient of friction of these composites. Experimental results indicate considerable grain refinement and improvement in the microhardness of these composites after the addition of CNTs/GNPs in the nickel matrix. In addition, the CNTs and GNPs were effective in forming a lubricant layer, enhancing the wear resistance and lowering the coefficient of friction during the sliding wear test, in contrast to the pure nickel counterpart. Pure nickel demonstrated the highest CoF of ~0.9, Ni-0.5CNT and Ni-0.5GNP exhibited a CoF of ~0.8, whereas the lowest CoF of ~0.2 was observed for Ni-2CNT and Ni-5GNP composites. It was also observed that the uncertainty of wear resistance and CoF in both the CNT/GNP-reinforced composites increased when loaded with higher reinforcement concentrations. The wear surface was analyzed using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analysis to elucidate the wear mechanism in these composites.     

Effects of Basalt and Carbon Fillers on Fire Hazard,Thermal, and Mechanical Properties of EPDM Rubber Composites

Due to growing restrictions on the use of halogenated flame retardant compounds, there is great research interest in the development of fillers that do not emit toxic compounds during thermal decomposition. Polymeric composite materials with reduced flammability are increasingly in demand. Here, we demonstrate that unmodified graphene and carbon nanotubes as well as basalt fibers or flakes can act as effective flame retardants in polymer composites. We also investigate the effects of mixtures of these carbon and mineral fillers on the thermal, mechanical, and rheological properties of EPDM rubber composites. The thermal properties of the EPDM vulcanizates were analyzed using the thermogravimetric method. Flammability was determined by pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry.     

Elastic Recovery Properties of Ultralight Carbon Nanotube/Carboxymethyl Cellulose Composites

Ultralight materials exhibit superelastic behavior depending on the selection, blending, and carbonization of the materials. Recently, ultimate low-density materials of 5 mg/cm³ or less have attracted attention for applications such as sensors, electrodes, and absorbing materials. In this study, we fabricated an ultralight material composed of single-walled carbon nanotubes (CNT) and sodium carboxymethyl cellulose (CMC), and we investigated the effect of density, composition, and weight average molecular weight of CMC on elastic recovery properties of ultralight CNT/CMC composites. Our results showed that the elastic recovery properties can be improved by reducing the density of the composite, lowering the mass ratio of CNTs, and using CMC with small molecular weight.     

Liquid Guayule Natural Rubber,a Sustainable Processing Aid,Enhances the Processability,Durability and Dynamic Mechanical Properties of Rubber Composites

Petroleum-based oils are widely used as processing aids in rubber composites to improve processability but can adversely affect rubber composite performance and increase carbon footprint. In this research, liquid guayule natural rubber (LGNR), produced from guayule natural rubber, was used as a renewable processing aid to replace naphthenic oil (NO) in Hevea natural rubber, styrene-butadiene rubber (SBR) and guayule natural rubber (GNR) composites. The rheological properties, thermal stability, glass transition temperature, dynamic mechanical properties, aging, and ozone resistance of rubber composites with and without NO or LGNR were compared. Natural and synthetic rubber composites made with LGNR had similar processability to those made with NO, but had improved thermal stability, mechanical properties after aging, and ozone resistance. This was due to the strong LGNR–filler interaction and additional crosslinks formed between LGNR and the rubber matrices. The glass transition temperature of SBR composites was reduced by LGNR because of its increased molecular mobility. Thus, unlike NO, LGNR processing aid can simultaneously improve rubber composite durability, dynamic performance and renewability. The commercialization of LGNR has the potential to open a new sustainable processing-aid market.     

Investigation of Ramped Compression Effect on the Dielectric Properties of Silicone Rubber Composites for the Coating of High-Voltage Insulation

The incorporation of inorganic oxide fillers imparts superior dielectric properties in silicone rubber for high-voltage insulation. However, the dielectric characteristics are influenced by the mechanical stress. The effects of ramped compression on the dielectric properties of neat silicone rubber (NSiR), 15% SiO₂ microcomposite (SSMC), 15% alumina trihydrate (ATH) microcomposite (SAMC) and 10% ATH + 2% SiO₂ hybrid composite (SMNC) are presented in this study. The dielectric constant and dissipation factor were measured before and after each compression especially in the frequency range of 50 kHz to 2MHz. Before the compression, SSMC expressed the highest dielectric constant of 4.44 followed by SMNC and SAMC. After the compression cycle, SAMC expressed a better dielectric behavior exhibiting dielectric constant of 7.19 and a dissipation factor of 0.01164. Overall, SAMC expressed better dielectric response before and after compression cycle with dielectric constant and dissipation factor in admissible ranges.     

Mechanical Behavior of Plaster Composites Based on Rubber Particles from End-of-Life Tires Reinforced with Carbon Fibers

The principal objective of this research project is the disposal of end-of-life tire rubber waste and its incorporation in gypsum composites. As a continuation of previous projects, which established a reduction in the mechanical properties of the resulting products, the behavior of these composites is analyzed with the incorporation of carbon fibers. The density, Shore C hardness, flexural strength, compressive strength, dynamic modulus of elasticity, strength–strain curves, toughness and resistance values and microstructure of the material are studied and compared. The results obtained show a significant increase in the mechanical tensile strength of all of the samples containing fibers. The moduli of elasticity results show a decrease in rigidity and increase in toughness and resistance of the material produced by incorporating the fibers. An optimum dosage of a water/gypsum ratio of 0.6 and incorporation of 1.5% carbon fibers is proposed. This lightweight material, which offers a high mechanical performance, features characteristics which are suitable for large prefabricated building elements in the form of panels or boards.     

Enhancement on the Tribological Properties of the Multilayer RGO/Al Matrix Composites by Cu-Coating Method

Multilayer reduced graphene oxide (mrGO) was chemically modified by electroless plating of copper on surface to form mrGO-Cu. The scanning electron microscope (SEM) and transmission electron microscope (TEM) analysis revealed that nano-Cu particles were uniformly dispersed on the surface of mrGO. The mrGO-Cu powders were further utilized as reinforcements for aluminum (Al) matrix and the mrGO-Cu/Al composite was successfully fabricated through clad rolling of milled powder. The tribological properties of the mrGO-Cu/Al composites were explored. The tribological results show that the mrGO-Cu could reduce the friction coefficient and wear loss of mrGO-Cu/Al composites, since the mrGO-Cu participated in lubricating processes due to the formation of a transfer layer on the contact surface. Furthermore, it is found that the composition of mrGO-Cu could significantly influence the tribological properties of the mrGO-Cu/Al composites. The composites with 4% of mrGO-Cu for composites exhibited the best tribological behavior, which transformed from adhesive wear to abrasive wear, due to the formation of a graphite lubricating film.     

Metal/Graphene Composites: A Review on the Simulation of Fabrication and Study of Mechanical Properties

Although carbon materials, particularly graphene and carbon nanotubes, are widely used to reinforce metal matrix composites, understanding the fabrication process and connection between morphology and mechanical properties is still not understood well. This review discusses the relevant literature concerning the simulation of graphene/metal composites and their mechanical properties. This review demonstrates the promising role of simulation of composite fabrication and their properties. Further, results from the revised studies suggest that morphology and fabrication techniques play the most crucial roles in property improvements. The presented results can open up the way for developing new nanocomposites based on the combination of metal and graphene components. It is shown that computer simulation is a possible and practical way to understand the effect of the morphology of graphene reinforcement and strengthening mechanisms.     

Preparation and Properties of SBR Composites Containing Graphene Nanoplatelets Modified with Pyridinium Derivative

The goal of this work was to study the effect of graphene nanoplatelets (GnPs) modified with ionic liquid (IL) on properties of styrene–butadiene rubber (SBR) composites. GnPs were decorated with IL or were modified in bulk directly during rubber mix preparation. The ionic liquid used was 1-butyl-4-methylpyridinium tetrafluoroborate (BMPFB). The textural properties were studied to confirm surface modification of GnPs with BMPFB. In these investigations, the impact of the concentration of GnPs and the effect of the method of GnPs’ modification with IL on elastomers properties are described. Some thermal measurements (e.g., differential scanning calorimetry and thermogravimetry) were conducted to characterize the thermal stability or the vulcanization process of the investigated samples. Complementary experimental techniques were used to investigate the properties of the obtained elastomers, specifically tensile testing, and electrical and barrier property measurements. The deposition of IL on the GnPs’ surface positively influenced the mechanical and barrier properties of elastomers. However, samples containing graphene nanoplatelets modified from solution were characterized by less electrical conductivity. SEM analysis was additionally performed to investigate GnPs’ dispersion within SBR composites.     

Evolution of Microstructure,Texture and Mechanical Properties for Multilayered Al Matrix Composites by Accumulative Roll Bonding

Carbon nanotubes (CNTs) reinforced aluminum matrix nanocomposites were fabricated by Accumulative Roll Bonding (ARB). The surface morphologies, mechanical properties, grains texture and orientation of the Al/CNTs nanocomposites were characterized, and the mechanisms and influences of CNTs contents and ARB cycles on the mechanical performance and grain textures of Al/CNTs were investigated and revealed. The strength of the composites rose with increase of the CNTs content, and the ARB cycles showed a 26% improvement when the CNTs content varied from 0 to 1 volume percent (vol.%). The increase in the mass fraction of the carbon nanotubes made the grain distribution in the Al/CNTs nanocomposite samples more diffuse. Besides, the stable texture of the hot rolled crystal grains on the α orientation are constantly turning to {011}< 011> with the mass fraction of the reinforcing phase increased.     

Effect of Polymer Additives on the Microstructure and Mechanical Properties of Self-Leveling Rubberised Concrete

The materials based on concrete with an addition of rubber are well-known. The interaction between concrete components and rubber particles is in the majority cases insufficient. For this reason, different substances are introduced into concrete-rubber systems. The aim of this paper is to establish the influence of five different polymer additives, i.e., 1. an aqueous dispersion of a styrene-acrylic ester copolymer (silanised) (ASS), 2. water dispersion of styrene-acrylic copolymer (AS), 3. anionic copolymer of acrylic acid ester and styrene in the form of powder (AS.RDP), 4. water polymer dispersion produced from the vinyl acetate and ethylene monomers (EVA), 5. copolymer powder of vinyl acetate and ethylene (EVA.RDP)) on the properties of the self-leveling rubberised concrete. Scanning electron microscopy has allowed to establish the interaction between the cement paste and rubber aggregates. Moreover, the compressive strength and flexural strength of the studied materials were evaluated. The results indicate that the mechanical properties depend extensively on the type as well as the amount of the polymer additive introduced into the system.     

Study on Rheological Properties of Graphene Oxide/Rubber Crowd Composite-Modified Asphalt

In order to improve the durability of asphalt pavement and prolong the service life of heavy traffic asphalt pavement, graphene oxide (GO) and rubber powder (RP) were used as composite modifiers to modify matrix asphalt. The high-temperature rheological properties of composite-modified asphalt at different temperatures and frequencies were analyzed. The influence of different stress levels on the viscoelastic properties of composite-modified asphalt was evaluated. The low-temperature rheological properties of composite-modified asphalt were studied. The difference between RP-modified asphalt and GO/RP composite-modified asphalt was analyzed, and the mechanism of GO and RP on asphalt modification was explored. The results show that the composite-modified asphalt has good rheological properties at low temperature, relatively smooth surface and stable network structure, which improves the segregation problem of RP in matrix asphalt. At present, GO and RP are rarely used as composite modifiers to modify matrix asphalt at home and abroad, which is an innovation in material selection.     

Carbon Nanomaterials for Enhancing the Thermal,Physical and Rheological Properties of Asphalt Binders

Effective thermal conduction modification in asphalt binders is beneficial to reducing pavement surface temperature and relieving the urban heat island (UHI) effect in the utilization of solar harvesting and snow melting pavements. This study investigated the performance of two nanometer-sized modifiers, graphene (Gr) and carbon nanotubes (CNTs), on enhancing the thermal, physical and rheological properties of asphalt binders. Measurements depending on a transient plant source method proved that both Gr and CNTs linearly increased the thermal conductivity and thermal diffusivity of asphalt binders, and while 5% Gr by volume of matrix asphalt contributed to 300% increments, 5% CNTs increased the two parameters of asphalt binders by nearly 72% at 20 °C. Meanwhile, a series of empirical and rheological properties experiments were conducted. The results demonstrated the temperature susceptibility reduction and high-temperature properties promotion of asphalt binders by adding Gr or CNTs. The variation trends in the anti-cracking properties of asphalt binders modified by Gr and CNTs with the modifier content differed at low temperatures, which may be due to the unique nature of Gr. In conclusion, Gr, whose optimal content is 3% by volume of matrix asphalt, provides superior application potential for solar harvesting and snow melting pavements in comparison to CNTs due to its comprehensive contributions to thermal properties, construction feasibility, high-temperature performance and low-temperature performance of asphalt binders.     

The Use of Copper Oxides as Cross-Linking Substances for Chloroprene Rubber and Study of the Vulcanizates Properties. Part II. The Effect of Filler Type on the Properties of CR Products

The properties of rubber materials are dependent on the characteristics of the elastomer matrix, the filler type, the cross-linking agent, the number of ingredients, and their interactions. In the previous article, we showed that chloroprene rubber can be efficiently cross-linked with copper(I) oxide or copper(II) oxide. During the processing of rubber compounds, the incorporation of a filler and a curing substance are two substantial parameters, such as the homogeneity of mixing and cross-linking that significantly affect the properties of the vulcanizates. Therefore, this work aimed to evaluate the curing characteristics, mechanical and dynamical properties, morphology, and flammability of the composites containing chloroprene rubber cross-linked with Cu₂O or CuO and filled with different fillers (silica, carbon black, montmorillonite, kaolin, chalk). It was found that the type of filler and curing agent had a significant impact on the degree of cross-linking of the chloroprene rubber and the properties of its vulcanizates. The degree and speed of the cross-linking of filled CR were higher when the CR was cured with copper(II) oxide. Among the fillers used, the presence of carbon black or silica ensured the highest degree of CR cross-linking and the most useful properties. The flammability tests indicated that all produced vulcanizates were characterized by a high oxygen index, which allows them to be classified as non-flammable materials.     

A Sequenced Study of Improved Dielectric Properties of Carbon Nanotubes and Metal Oxide-Reinforced Polymer Composites

Polymers have gained attraction at the industrial level owing to their elastic and lightweight nature, as well as their astonishing mechanical and electrical applications. Their scope is limited due to their organic nature, which eventually leads to the degradation of their properties. The aim of this work was to produce polymer composites with finely dispersed metal oxide nanofillers and carbon nanotubes (CNTs) for the investigation of their charge-storage applications. This work reports the preparation of different polymeric composites with varying concentrations of metal oxide (MO) nanofillers and single-walled carbon nanotubes (SWCNTs). The successful synthesis of nanofillers (i.e., NiO and CuO) was carried out via the sonication and precipitation methods, respectively. After, the smooth and uniform polymeric composite thin films were prepared via the solution-casting methodology. Spectroscopy and diffraction techniques were used for the preliminary characterization. Scanning electron microscopy was used to check the dispersion of carbon nanotubes (CNTs) and MOs in the polymer matrix. The addition of nanofillers and carbon nanotubes (CNTs) tuned the bandgap, reduced the strain, and enhanced the elastic limit of the polymer. The addition of CNT enhanced the mechanical strength of the composite; however, it increased the conductivity, which was tuned by using metal oxides. By increasing the concentration of NiO and CuO from 2% to 6% bandgap of PVA, which is 5–6 eV reduced to 4.41 and 4.34 eV, Young’s moduli of up to 59 and 57.7 MPa, respectively, were achieved. Moreover, improved dielectric properties were achieved, which shows that the addition of metal oxide enhances the dielectric behavior of the material.     

Effect of Fiber Content and Alignment on the Mechanical Properties of 3D Printing Cementitious Composites

This paper studies aligned glass fiber-reinforced composites for printing. To determine the influence of fiber content and alignment on the mechanical properties of this novel material, a large number of standard test specimens were prepared, which included samples fabricated by mold-casting, randomly dispersed fiber reinforced mixtures and aligned fiber cement composites containing 10 types of fiber volume ratios manufactured by nozzle sizes ranging of 24 and 10 mm (fiber length = 12 mm). Mechanical properties and failure modes of the specimens under compression and flexural tests were studied experimentally. The anisotropic behaviors of printed samples were analyzed by different loading directions. As a result, the compressive and flexural strength of printed samples showed obvious anisotropy. With the increase of fiber volume ratio, flexural strength of the fiber reinforced composite was elevated tremendously but its compression strength reduced slightly. Moreover, fiber alignment also had a significant influence on the mechanical properties of the fiber reinforced composite. The composite cement-based material with 1 vol.-% aligned fiber exhibited an excellent flexural strength of 9.38 MPa, which increased by 483% in comparison to that of the plain cement paste.     

The Impact of Graphene and Diatomite Admixtures on the Performance and Properties of High-Performance Magnesium Oxychloride Cement Composites

A high-performance magnesium oxychloride cement (MOC) composite composed of silica sand, diatomite powder, and doped with graphene nanoplatelets was prepared and characterized. Diatomite was used as a 10 vol.% replacement for silica sand. The dosage of graphene was 0.5 wt.% of the sum of the MgO and MgCl₂·6H₂O masses. The broad product characterization included high-resolution transmission electron microscopy, X-ray diffraction, X-ray fluorescence, scanning electron microscopy and energy dispersive spectroscopy analyses. The macrostructural parameters, pore size distribution, mechanical resistance, stiffness, hygric and thermal parameters of the composites matured for 28-days were also the subject of investigation. The combination of diatomite and graphene nanoplatelets greatly reduced the porosity and average pore size in comparison with the reference material composed of MOC and silica sand. In the developed composites, well stable and mechanically resistant phase 5 was the only precipitated compound. Therefore, the developed composite shows high compactness, strength, and low water imbibition which ensure high application potential of this novel type of material in the construction industry.