Widely dispersed PEI-based nanocomposites with multi-wall carbon nanotubes by blending with a masterbatch

High performance poly(etherimide) (PEI)-based nanocomposites (PNs) with multi-walled carbon nanotubes (MWCNT) were obtained via melt mixing. To achieve this, PEI was mixed with a well-dispersed commercial poly(butylene terephthalate) (PBT)/MWCNT master-batch in an attempt to transfer the dispersed MWCNTs to a PEI matrix. A broad and homogeneous dispersion of MWCNTs throughout the PEI-based matrix was obtained. The electrical percolation threshold (p_c) was reached at only 1 wt.% MWCNT. This p_c showed a power law dependence of conductivity on filler concentration, with a critical exponent of 1.92, which indicates that a three dimensional percolated structure was achieved. The glass transition temperature and the pressure at the output end of the extruder decreased when the master-batch was added, indicating that the processability of PEI was improved. In addition to this, the modified PEI-based PNs presented ductile behaviour and an ameliorated (12% with 5 wt.% MWCNT) elastic modulus compared with pure PEI.     

Study on thermal properties of graphene foam/graphene sheets filled polymer composites

The polymer composites composed of graphene foam (GF), graphene sheets (GSs) and pliable polydimethylsiloxane (PDMS) were fabricated and their thermal properties were investigated. Due to the unique interconnected structure of GF, the thermal conductivity of GF/PDMS composite reaches 0.56 W m⁻¹ K⁻¹, which is about 300% that of pure PDMS, and 20% higher than that of GS/PDMS composite with the same graphene loading of 0.7 wt%. Its coefficient of thermal expansion is (80–137) × 10⁻⁶/K within 25–150 °C, much lower than those of GS/PDMS composite and pure PDMS. In addition, it also shows superior thermal and dimensional stability. All above results demonstrate that the GF/PDMS composite is a good candidate for thermal interface materials, which could be applied in the thermal management of electronic devices, etc.     

Functionalizing graphene decorated with phosphorus-nitrogen containing dendrimer for high-performance polymer nanocomposites

In this paper, we demonstrate a novel strategy for fabricating advanced polymer composites based on functionalized graphene oxide decorated with phosphorus-nitrogen-containing dendrimers (PND-GO). Both X-ray diffraction and transmission electron microscopy results show that reduced PND-GO uniformly disperses within polymer matrix and is exfoliated in polyurethane (PU) via in situ polymerization. Cone calorimetry results show that incorporating 2 wt% reduced PND-GO into PU decreases the peak heat release rate by 53% and prolongs the time to ignition by 28 s as compared with the PU bulk. Besides, the tensile strength and Young’s modulus are remarkably enhanced by about 2 times and 5 times, respectively.     

Magnetically-sensitive shape memory polyurethane composites crosslinked with multi-walled carbon nanotubes

Magnetically-sensitive polyurethane composites, which were crosslinked with multi-walled carbon nanotubes (MWCNTs) and were filled with Fe₃O₄ nanoparticles, were synthesized via in situ polymerization method. MWCNTs pretreated with nitric acid were used as crosslinking agents. Because of the crosslinking of MWCNTs with polyurethane prepolymer, the properties of the composites with a high content of Fe₃O₄ nanoparticles, especially the mechanical properties, were significantly improved. The composites showed excellent shape memory properties in both 45 °C hot water and an alternating magnetic field (f = 45 kHz, H = 29.7 kA m⁻¹). The shape recovery time was less than one minute and the shape recovery rate was over 95% in the alternating magnetic field.     

Solvothermal synthesis of carbon nanostructure and its influence on thermal stability of poly styrene

Carbon nanostructures were synthesized via a novel solvothermal reaction between ferrocene and sulfur. Carbon nanostructures were then added to poly styrene (PS) matrix. The thermal stability behavior of PS filled with carbon nanostructures were investigated by thermogravimetric analysis (TGA). Nanostructures were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, energy-dispersive X-ray (EDS) analysis and atomic force microscopy (AFM). The flame retardancy behavior of PS–carbon was studied by UL-94 analysis.     

The synthesis of graphene nanoribbon and its reinforcing effect on poly (vinyl alcohol)

The graphene nanoribbon was prepared from the carbon nanotubes using the chemical approach, and was used for preparing the poly (vinyl alcohol) nanocomposites. It was discovered that the prepared graphene nanoribbon contained a lot of oxygen groups. Due to the presence of these oxygen groups, the nanoribbon could homogeneously disperse in both water and poly (vinly alcohol) matrix. It was also found that there were strong interactions between the graphene nanoribbon and the poly (vinyl alcohol) through hydrogen bonding. The interactions gave rise to the thermal stability of the host polymer. Furthermore, the presence of the nanofiller also resulted in a significant improvement of the mechanical performance of the prepared nanocomposites. The tensile strength and the Young’s modulus of the nanocomposite loaded with 2.0 wt% graphene nanoribbon increased by 85.7% and 65.2% respectively. The overall results indicate that the graphene nanoribbon is suitable for preparing high-performance polymer composites.     

Synthesis of polypyrrole nanocomposites decorated with silver nanoparticles with electrocatalysis and antibacterial property

Polypyrrole nanowire/silver nanoparticle composites (PPy/Ag) are obtained in aqueous media through a one-pot method without any external stimulus. PPy nanowires were assembled on the reactive self-degraded template of the complex of AgNO₃ and methyl orange (MO). During the synthesis process in the dark surrounding, Ag nanoparticles could be uniformly decorated onto the surface of PPy nanowires in situ by the redox reaction of pyrrole and AgNO₃. Neither additional reducing agents for the growth of silver nanoparticles nor oxidizing agents for the polymerization of pyrrole are utilized. The formation mechanism, morphologies, structural characteristics, and conductivity of the obtained PPy/Ag nanocomposites are reported. The as-prepared PPy/Ag nanocomposites exhibit well-defined response to the electrochemical reduction of hydrogen peroxide. Moreover, the preliminary antibacterial assays indicate that the PPy/Ag nanocomposites also possess antibacterial abilities against Escherichia coli.     

Evaluation of thermal,mechanical, and electrical properties of PVDF/GNP binary and PVDF/PMMA/GNP ternary nanocomposites

Graphene nanoplatelet (GNP) was incorporated into poly(vinylidene fluoride) (PVDF) and PVDF/poly(methyl methacrylate) (PMMA) blend to achieve binary and ternary nanocomposites. GNP was more randomly dispersed in binary composites compared with ternary composites. GNP exhibited higher nucleation efficiency for PVDF crystallization in ternary composites than in binary composites. GNP addition induced PVDF crystals with higher stability; however, PMMA imparted opposite effect. The binary composite exhibited lower thermal expansion value than PVDF; the value further declined (up to 28.5% drop) in the ternary composites. The storage modulus of binary and ternary composites increased to 23.1% and 53.9% (at 25 °C), respectively, compared with PVDF. Electrical percolation threshold between 1 phr and 2 phr GNP loading was identified for the two composite systems; the ternary composites exhibited lower electrical resistivity at identical GNP loadings. Rheological data confirmed that the formation of GNP (pseudo)network structure was assisted in the ternary system.     

Facile preparation of graphene nanoribbon filled silicone rubber nanocomposite with improved thermal and mechanical properties

In the present study, graphene nanoribbon was prepared through unzipping the multi walled carbon nanotubes, and its reinforcing effect as a filler to the silicone rubber was further investigated. The results showed that carbon nanotubes could be unzipped to graphene nanoribbon using strong oxidants like potassium permanganate and sulfuric acid. The prepared graphene nanoribbon could homogeneously disperse within silicone rubber matrix using a simple solution mixing approach. It was also found from the thermogravimetric analysis curves that the thermal stability of the graphene nanoribbon filled silicone rubber nanocomposites improved compared to the pristine silicone rubber. Besides, with the incorporation of the nanofiller, the mechanical properties of the resulting nanocomposites were significantly enhanced, in which both the tensile stress and Young’s modulus increased by 67% and 93% respectively when the mass content of the graphene nanoribbon was 2.0 wt%. Thus it could be expected that graphene nanoribbon had large potentials to be applied as the reinforcing filler to fabricate polymers with increased the thermal and mechanical properties.     

Creep behavior of polyurethane nanocomposites with carbon nanotubes

The polyurethane (PU) nanocomposites containing carbon nanotubes (CNTs) were prepared through in situ polymerization for the creep study. The results show that the presence of CNTs leads to a significant improvement of creep resistance of PU. However, this creep resistance does not increase monotonously with increase of CNT contents because it is highly dependent on the dispersion of CNTs. Several theoretical models were then used to establish the relations between CNT dispersion and final creep and creep–recovery behaviors of nanocomposites. The as-obtained viscoelastic and viscoplastic parameters of PU matrix and structural parameters of CNTs further confirmed the retardation effect by CNTs during creep of the nanocomposite systems. Besides, the time–temperature superposition (TTS) principle was also employed in this work to make a further evaluation on the creep of PU/CNT nanocomposites with long-term time scale.     

Aligning carbon nanotubes using bulk acoustic waves to reinforce polymer composites

Bulk acoustic waves (BAWs) are used to align multi-walled carbon nanotubes (MWCNTs) in polymer composite materials. MWCNTs are first dispersed in the liquid state of a thermoset resin and aligned using standing BAWs. Cross-linking of the resin fixates the aligned MWCNTs in the polymer matrix material. We have quantified the alignment obtained with this method on the macro, micro, and nanoscale, and it is found to be similar to other alignment techniques such as stretching, slicing, and wet spinning. The elastic modulus and ultimate tensile strength of composite material specimens with aligned MWCNTs, fabricated using this technique, are evaluated and compared with specimens consisting of randomly oriented MWCNTs and resin material without MWCNTs. Different MWCNT loading rates are considered. The elastic modulus of composite material specimens with only 0.15 weight percent aligned MWCNTs is observed to be 44% higher than specimens with randomly oriented MWCNTs, and 51% higher than specimens without MWCNTs. However, further increasing the MWCNT loading rate does not significantly increase the elastic modulus and ultimate tensile strength, likely because of insufficient dispersion of MWCNTs in the thermoset matrix material.     

Facile preparation,characterization and performance of noncovalently functionalized graphene/epoxy nanocomposites with poly(sodium 4-styrenesulfonate)

Graphene was noncovalently functionalized with poly(sodium 4-styrenesulfonate) (PSS) and then successfully incorporated into the epoxy resin via in situ polymerization to form functional and structural nanocomposites. The morphology and structure of PSS modified graphene (PSS-g) were characterized with transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The effects of PSS-g additions on tensile, electrical and thermal properties of the epoxy/graphene nanocomposites were studied. Noncovalent functionalization improved interfacial bonding between the epoxy matrix and graphene, leading to enhanced tensile strength and modulus of resultant nanocomposites. The PSS-g additions also enhanced electrical properties of the epoxy/PSS-g nanocomposites, resulting in a lower percolation threshold of 1.2 wt%. Thermogravimetric and differential scanning calorimetric results showed the occurrence of a two-step decomposition process for the epoxy/PSS-g nanocomposites.     

Enhancement of tensile and thermal properties of epoxy nanocomposites through chemical hybridization of carbon nanotubes and alumina

This paper presents the properties of epoxy nanocomposites, prepared using a synthesized hybrid carbon nanotube–alumina (CNT–Al₂O₃) filler, via chemical vapour deposition and a physically mixed CNT–Al₂O₃ filler, at various filler loadings (i.e., 1–5%). The tensile and thermal properties of both nanocomposites were investigated at different weight percentages of filler loading. The CNT–Al₂O₃ hybrid epoxy composites showed higher tensile and thermal properties than the CNT–Al₂O₃ physically mixed epoxy composites. This increase was associated with the homogenous dispersion of CNT–Al₂O₃ particle filler; as observed under a field emission scanning electron microscope. It was demonstrated that the CNT–Al₂O₃ hybrid epoxy composites are capable of increasing tensile strength by up to 30%, giving a tensile modulus of 39%, thermal conductivity of 20%, and a glass transition temperature value of 25%, when compared to a neat epoxy composite.     

Influences of clay and manufacturing on fire resistance of organoclay/thermoset nanocomposites

The organoclay GFRP nanocomposites are prepared using the vacuum assisted resin transfer moulding method. Two grades of organophilic clay with three content levels, three types of thermosetting resins (polyester, vinyl ester and epoxy), and three nanoclay dispersion techniques are investigated. To understand the effects of these factors on the fire performance, Taguchi design of experiments (DoE) method is employed and preferred combinations of factors are determined using a one-step and a proposed two-step GLM ANOVA. The one-step ANOVA is applied directly on the experimental results, while the two-step ANOVA is conducted on the signal-to-noise ratios obtained from the Taguchi analysis. The combination of mechanical and ultrasonic dispersing procedure has been found to have considerable influence on the of nanoclay distribution. While both approaches provide insights into the influences of each fabrication factor, the two-step gives a better prediction of the favourable response combination for the nanocomposites when validated with experiments.     

Preparation and tribological performance of chemically-modified reduced graphene oxide/polyacrylonitrile composites

Interface control and dispersion of graphene base nanomaterials in polymer matrix are challenging to develop high comprehensive nanocomposites due to their strong interlayer cohesive energy and chemical inertia. In this research, an efficient approach is presented to functionalize reduced graphene oxide nanosheets by N-[3-(trimethoxylsilyl)propyl]ethylenediamine, which is dispersed into polyacrylonitrile to prepare N-[3-(trimethoxylsilyl)propyl]ethylenediamine – reduced graphene oxide/polyacrylonitrile nanocomposites. A thermogravimetric analysis technique was employed to evaluate thermal properties of the nanocomposites. The tribological properties of the polyacrylonitrile/graphene nanocomposites were investigated. The morphologies and volume of the worn surface were examined using a 3D profilometer. The impact of loading ratio on friction coefficient, carry-bearing capacity and durability were studied. The N-[3-(trimethoxylsilyl)propyl]ethylenediamine – reduced graphene oxide/polyacrylonitrile nanocomposite with appropriate loading ratio of reduced graphene oxide exhibited a high load-bearing capacity and durability. Therefore, the polyacrylonitrile/graphene nanocomposite shows promising potential to industrial applications involving the lubrication and anti-wear.     

Engineering the coefficient of thermal expansion and thermal conductivity of polymers filled with high aspect ratio silica nanofibers

The thermomechanical properties of epoxy filled with two different types of silica nanofillers: spherical nanoparticles and nanofibers were investigated as a function of silica nanofiller aspect ratio and concentration. Results indicated that at room temperature and at 8.74% silica nanofiber concentration (by volume) the thermal conductivity of epoxy increased twofold and coefficient of thermal expansion (CET) decreased by ∼40%. Silica nanofiber filled epoxy showed 1.4 times greater CET and 1.5 times greater thermal conductivity compared to spherical nanoparticle filled epoxy. The significant changes observed in thermomechanical properties of silica nanofiber filled epoxy were attributed to its high aspect ratio by constraining the polymer matrix as well as reducing the phonon scattering due to the formation of a continuous fiber network within the matrix. In addition to being electrically insulating, the improved properties of silica nanofiber filled epoxy make it an extremely attractive material as underfill and encapsulant in advanced electronic packaging industry.     

Enhancement of pullout energy in a single-walled carbon nanotube-polyethylene composite system via auxetic effect

Inter-tube bridging of carbon nanotubes (CNTs) is a reliable way to improve the inter-tube stress transfer abilities. The work describes the interfacial interactions provided by a wall-to-wall inter-tube bridging between two single-walled carbon nanotubes (SWCNTs) embedded in a polyethylene (PE) matrix. Molecular dynamics (MD) models of tube pullout phenomena represent by the embedding (10, 10)–(10, 10) SWCNT with interconnections into an amorphous PE matrix. The simulations show that the inter-tube bridging enhances the pullout energies significantly due to the three energy dissipative micro-mechanisms: stress-induced tube deformation with localized auxetic effect, “cutting through” (penetration) between linker and matrix, and the accompanying tube pullout. Moreover, the results also predict that linkers with longer aliphatic chains or aromatic rings provide further increase to the levels of the nanotube pullout energies. These are of potential importance in guiding the design of CNT/polymer composites through inter-tube linkage.     

Modification of montmorillonite by novel geminal benzimidazolium surfactant and its use for the preparation of polymer organoclay nanocomposites

A new benzimidazolium derivative, the benzimidazolium-N,N′-hexadecane-2-hydroxy-ethyl bromide (Bz) featuring two geminal hexadecyl hydrophobic buttress has been synthesized and used for the functionalization of sodium montmorillonite (MMT-Na) via cationic exchange process. The resulting benzimidazolium-modified MMT (MMT-Bz) exhibits a large d-spacing of 3 nm between silicate layers and shows a high thermal stability compared to the commonly used clay modified alkyl ammonium salts (cloisite 20A and cloisite 20B). MMT-Bz was incorporated in high density polyethylene (HDPE) matrix via melt mixing method to produce HDPE/MMT-Bz nanocomposites. The microstructure and the morphology of these nanocomposites were studied by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The dispersion state of the organoclay within HDPE was monitored by UV–Vis spectroscopy and melt rheology. A more homogeneous dispersion or a greater content of the MMT-Bz in the matrix produced stronger solid-like and non-terminal behavior in the nanocomposites. Tensile properties and thermal stability were evaluated and discussed on the basis of the amount of clay incorporated within the nanocomposites. The intercalated structure in the nanocomposites, resulting from both the better dispersion/distribution of clay nano-platelets and their strong interaction with the polymer chains, provides the driving force to significantly enhance the HDPE properties.     

Growing polystyrene chains from the surface of graphene layers via RAFT polymerization and the influence on their thermal properties

The polystyrene (PS) macromolecular chains were grafted on the surface of graphene layers by reversible addition-fragmentation chain transfer (RAFT) polymerization. In this procedure, a RAFT agent, 4-Cyano-4-[(dodecylsulfanylthiocarbonyl) sulfanyl] pentanoic acid, was used to functionalize the thermal reduced graphene oxide (TRGO) to obtain the precursor (TRGO-RAFT). It can be calculated that the grafting density of PS/graphene (PRG) composites was about 0.18 chains per 100 carbons. Successful in-plain attachment of RAFT agent to TRGO and PS chain to TRGO-RAFT was shown an influence on the thermal property of the PRG composites. The thermal conductivity (λ) improved from 0.150 W m⁻¹ K⁻¹ of neat PS to 0.250 W m⁻¹ K⁻¹ of PRG composites with 10 wt% graphene sheets loading. The thermal property of PRG composites increased due to the homogeneous dispersion and ordered arrangement of graphene sheets in PS matrix and the formation of PRG composites.