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.     

In situ preparation of reinforced polyimide nanocomposites with the noncovalently dispersed and matrix compatible MWCNTs

High performance MWCNT-reinforced polyimide nanocomposites were prepared through in situ polymerization route. 2,6-Diaminoanthraquinone (2,6-DAAQ) was selected to serve as both a diamine comonomer, and a noncovalent dispersant of MWCNTs through π–π interaction. The good dispersion of MWCNTs in both solution and polymer matrix, and high compatibility derived from the structural similarity have been proved to be particularly advantageous for the interfacial adhesion and load transfer from the polymer matrix to MWCNTs. The nanocomposites with 0.50–0.75 wt% MWCNTs had the most excellent thermal stability, thermomechanical and tensile properties, and the electrical conductivity also achieved a sharp increase at such low content. The load transfer efficiency was calculated based on both theoretical model and microscopical size measurement, and the results were rather reasonable within accepted error range.     

Thermo-mechanical properties of polysulfone based nanocomposites with well dispersed silica nanoparticles

The effect of the filler on the thermo-mechanical properties of polysulfone filled nanocomposites was studied considering different loads of silica nanoparticles (0, 1, 2, 5 and 10 wt%). Thermal characterization showed that: (i) the degradation temperature slightly increases with the content of particles; (ii) glass transition temperature is not affected by the presence of the particles, suggesting a weak interaction between the matrix and the particles. Although thermogravimetric analysis indicate there may be certain favorable interactions between the polymer and the filler, they must not be so important as to reduce chain mobility nearby the surface of the particles. Mechanical properties (modulus of rupture, hardness, indentation modulus, etc.) remain almost constant up to relatively high contents of nanoparticles (5 wt%). A significant increase was only observed for the sample with 10% of nanoparticles suggesting that, in this system, interconnection between particles must exist to efficiently modify the polysulfone properties.     

Temperature sensing with fluorescence intensity ratio technique in epoxy-based nanocomposite filled with Er-doped 7YSZ

Luminescent nanocomposite of epoxy filled with Er³⁺-doped yttria-stabilized zirconia (7YSZ) is prepared with their luminescence spectra measured in the temperature range 123–423 K. Fluorescence intensity ratio (FIR) of the two Er³⁺ emissions is also obtained in the same temperature range. Er–7YSZ/epoxy nanocomposites exhibited higher sensitivity of 0.18%/K as compared with the bare Er–7YSZ particles. Luminescence thermometry is demonstrated by using the nanocomposites as temperature sensitive paint (TSP) with a resolution of 1 K. The advantage of FIR technique combined with the excellent thermal stability of epoxy matrix makes the Er–7YSZ/epoxy nanocomposites viable as temperature sensitive paint for aerodynamic applications.     

Effect of filler size and concentration on the structure and properties of poly(vinylidene fluoride)/BaTiO<Subscript>3</Subscript> nanocomposites

The effect of filler size and content in the thermal, mechanical, and electrical response of poly(vinylidene fluoride) (PVDF)/BaTiO₃ nanocomposites has been investigated. Dielectric constant increases significantly with increasing filler content and decreasing filler size. Space charge effects at the interface between BaTiO₃ and PVDF strongly influence the dielectric response. The electroactive β-phase of PVDF is nucleated by the presence of the ceramic filler, the effect being strongly dependent on filler size and independent on filler content. This filler/matrix interaction is also responsible for the variations observed in the activation energy of the thermal degradation of the polymer. Smaller particles lead to larger relative contact areas and are responsible for the main variations observed in the thermal, mechanical, and electrical properties of the composites.     

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.     

Morphology and properties of injection-moulded carbon-nanofibre poly(etheretherketone) foams

Poly(ether ether ketone) (PEEK) is a high performance polymer that cannot usually be foamed reliably using conventional injection-moulding processes. Here, vapour-grown carbon nanofibres (CNFs) are introduced to stabilise the foaming process, and the resulting morphology of injection-moulded integral foams is investigated in detail. Different image analysis techniques revealed the positive effect of the nanofiller on the cellular structure. Electron microscopy confirmed a homogeneous dispersion of the nanofibres in the cellular PEEK cores. The mechanical properties of the foam injection-moulded samples, in bending, showed an increase in yield strength and elastic modulus with nanofibre loading fractions up to 15 wt%. Although the compressive properties of the foams were reduced as compared to the solid-polymer, the CNFs clearly offset this reduction in properties. Detailed differential scanning calorimetry (DSC) and dynamic mechanical analysis provide further evidence of an interaction between the matrix and the nanoscale filler.     

Investigation of thermal conductivity and dielectric properties of LDPE-matrix composites filled with hybrid filler of hollow glass microspheres and nitride particles

The hybrid filler of hollow glass microspheres (HGM) and nitride particles was filled into low-density polyethylene (LDPE) matrix via powder mixing and then hot pressing technology to obtain the composites with higher thermal conductivity as well as lower dielectric constant (D_k) and loss (D_f). The effects of surface modification of nitride particles and HGMs as well as volume ratio between them on the thermal conductivity and dielectric properties at 1 MHz of the composites were first investigated. The results indicate that the surface modification of the filler has a beneficial effect on thermal conductivity and dielectric properties of the composites due to the good interfacial adhesion between the filler and matrix. An optimal volume ratio of nitride particles to HGMs of 1:1 is determined on the basis of overall performance of the composites. The thermal conductivity as well as dielectric properties at 1 MHz and microwave frequency of the composites made from surface-modified fillers with the optimal nitride to HGM volume ratio were investigated as a function of the total volume fraction of hybrid filler. It is found that the thermal conductivity increases with filler volume fraction, and it is mainly related to the type of nitride particle other than HGM. The D_k values at 1 MHz and microwave frequency show an increasing trend with filler volume fraction and depend largely on the types of both nitride particles and HGMs. The D_f values at 1 MHz or quality factor (Q × f) at microwave frequency show an increasing or decreasing trend with filler volume fraction and also depend on the types of both nitride particle and HGM. Finally, optimal type of HGM and nitride particles as well as corresponding thermal conductivity and dielectric properties is obtained. SEM observations show that the hybrid filler particles are agglomerated around the LDPE matrix particles, and within the agglomerates the smaller-sized nitride particles in the hybrid filler can easily form thermally conductive networks to make the composites with high thermal conductivity. At the same time, the increase of the value D_k of the composites is restricted due to the presence of HGMs.     

Structural Insight in the Interfacial Effect in Ferroelectric Polymer Nanocomposites

Both experimental results and theoretical models suggest the decisive role of the filler–matrix interfaces on the dielectric, piezoelectric, pyroelectric, and electrocaloric properties of ferroelectric polymer nanocomposites. However, there remains a lack of direct structural evidence to support the so-called interfacial effect in dielectric nanocomposites. Here, a chemical mapping of the interfacial coupling between the nanofiller and the polymer matrix in ferroelectric polymer nanocomposites by combining atomic force microscopy–infrared spectroscopy (AFM–IR) with first-principles calculations and phase-field simulations is provided. The addition of ceramic fillers into a ferroelectric polymer leads to augmentation of the local conformational disorder in the vicinity of the interface, resulting in the local stabilization of the all-trans conformation (i.e., the polar β phase). The formation of highly polar and inhomogeneous interfacial regions, which is further enhanced with a decrease of the filler size, has been identified experimentally and verified by phase-field simulations and density functional theory (DFT) calculations. This work offers unprecedented structural insights into the configurational disorder-induced interfacial effect and will enable rational design and molecular engineering of the filler–matrix interfaces of electroactive polymer nanocomposites to boost their collective properties.     

Electrical conductivity and Raman imaging of double wall carbon nanotubes in a polymer matrix

Raman spectroscopy is used to access the dispersion state of DWNTs in a PEEK polymer matrix. The interaction of the outer tube with the matrix can be determined from the line shape of the Raman G band. This allows us to distinguish regions where the nanotubes are well dispersed and regions where the nanotubes are agglomerated. The percolation threshold of the electrical conductivity of the double wall carbon nanotubes (DWNTs)/PEEK nanocomposites is found to be at 0.2-0.3 wt%. We find a maximum electrical conductivity of 3 × 10⁻² S cm⁻¹ at 2 wt% loading. We detect nanotube weight concentrations as low as 0.16 wt% by Raman spectroscopy using a yellow excitation wavelength. We compare the Raman images with transmission electron microscopy images and electrical conductivity measurements. A statistical method is used to find a quantitative measure of the DWNTs dispersion in the polymer matrix from the Raman images.     

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.     

Characterization and properties of in situ emulsion polymerized poly(methyl methacrylate)/graphene nanocomposites

Poly(methyl methacrylate) (PMMA)/graphene nanocomposites were prepared by in situ emulsion polymerization. Raman and Fourier transform infrared spectra showed that PMMA polymer contained partially reduced graphite oxide. Dynamic mechanical analysis and differential scanning calorimetry analysis showed that graphene in the PMMA matrix acted as reinforcing filler; it enhanced the storage moduli and glass transition temperatures of the nanocomposites. Thermogravimetric analysis showed that the thermal stability of the nanocomposites increased by ca. 35 °C. The electrical conductivity of nanocomposite with 3 wt.% graphite oxide was 1.5 S m⁻¹ at room temperature.     

Poly(ε-caprolactone)-based nanocomposites: Influence of compatibilization on properties of poly(ε-caprolactone)–silica nanocomposites

In the present paper, results about preparation and characterization of poly(ε-caprolactone) (PCL) based nanocomposites filled with silica nanoparticles are reported. In order to promote polymer/inorganic nanofiller compatibility and to increase the interfacial adhesion between the two components, silica nanoparticles surface has been functionalised by grafting a M_w = 10,000 Da PCL onto it. Successively, PCL based nanocomposites have been prepared by extrusion process. The relationships among size, amount of the nanofiller, organic coating and the final properties have been investigated. The morphological analysis has revealed that the silica functionalization can provide a useful method of preparation of the nanocomposites with the achievement of a fine, a good dispersion and a strong adhesion level. Thermal characterization has shown an improved thermal stability due to the presence of the silica nanoparticles, especially in the case of modified nanofillers. Finally mechanical tests revealed an increase of the Young’s modulus in the PCL based nanocomposites.     

Crystalline morphology and properties of multi-walled carbon nanotube filled isotactic polypropylene nanocomposites: Influence of filler size and loading

Isotactic polypropylene (PP) nanocomposites with multi-walled carbon nanotubes (MWCNTs) of various diameters (10–50 nm) were fabricated by extrusion and compression-molding techniques and characterized by X-ray diffraction measurements, differential scanning calorimetry, scanning electron microscopy, mechanical test and differential thermal analyses. The pure PP exhibits both the a- and b-axes oriented α-crystal, whereas the MWCNTs induce the b-axis orientation of the α-crystal along with the formation of minor γ-phase crystal in nanocomposites. Crystallinity, long period of lamellae, tensile strength, tensile modulus (TM) and microhardness (H) of PP considerably change by different loading and sizes of MWCNTs. The estimated values H/TM = 0.09–0.10 for all samples approach the predicted value of 0.10 for polymers. The increase in crystallinity has been demonstrated by both XRD and DSC studies. Mathematical models have been invoked to explain the changes in mechanical properties. An increase in thermal stability of polymer matrix occurs with increasing MWCNTs size and loading.     

Thermal conductivity and dynamic mechanical analysis of NiZn ferrite nanoparticles filled thermoplastic natural rubber nanocomposite

The effect of NiZn ferrite nanoparticles on the thermal behaviour of thermoplastic natural rubber (TPNR) composite is investigated. Melt blending technique was employed to prepare TPNR matrix, which comprised of natural rubber (NR), liquid natural rubber (LNR) and high-density polyethylene (HDPE) in a ratio of 20:10:70. Dynamic mechanical analysis results show that the thermal stability of the nanocomposites enhanced with increasing filler loading. Moreover, thermal conductivity of the nanocomposites increased with filler content until 8 wt%, which is believed to be the optimum loading that formed the suitable percolated network for phonon conduction facilitation.     

Polyethersulfone-expanded graphite nanocomposites: Charge transport and impedance characteristics

Polyethersulfone (PES)-expanded graphite nanocomposites have been prepared by solution blending route after sonicating expanded graphite in dichloromethane. It has been observed that ultrasonication results in nanosheets formation leading to a low percolation threshold of 3 wt.%. At 5 wt.% filler loading the conductivity is of the order of 10⁻² S/cm. Hopping type of charge transport occurs at 3.2 wt.% expanded graphite in PES below which capacitive effects couple. The effective dielectric constant at low frequency increases with filler concentration. Impedance measurement has been carried out to evaluate interfacial capacitance which, for 3.2 wt.% expanded graphite addition in PES, increases to 110 pF from 32 pF for 1 wt.% expanded graphite in the polymer. DSC analysis shows an increment of 12 °C in the T_g of PES with 3 wt.% expanded graphite suggesting interaction between the polymer and filler.     

Mechanical and thermal behavior of nanoclay based polymer nanocomposites using statistical homogenization approach

In the present study, the effects of nanoclay additives on the effective mechanical and thermal properties of polymer/nanoclay composites have been investigated using experimental and simulation analyzes. In this research, we propose the use of strong contrast statistical continuum theory to predict the effective elastic and thermal properties. To validate our modeling approach, we conducted experimental measurements of these properties for polyamide/nanoclay nanocomposites with concentrations of 1, 3 and 5 wt.% of nanoclay particles. Three-dimensional isotropic nanocomposite samples with randomly oriented monolayer nanoclays were computer generated and used to calculate the statistical correlation functions of the realized model. These correlation functions have been exploited to calculate effective thermal and elastic properties of the nanocomposite. The simulation results have shown that effective stiffness can be increased significantly with small amounts of particle concentration for the exfoliated clay monolayers. The predicted effective conductivity and elastic modulus have been compared to our experimental results. Effective thermal conductivity shows satisfactory agreement with experimental data. However, the predicted results for the elastic modulus overestimate the experimental data, which might be due to the increasing intercalated structure for high concentration of nanofiller and to anisotropic properties of the nanoclay.     

Effects of modified Clay on the morphology and thermal stability of PMMA/clay nanocomposites

The potential to improve the mechanical, thermal, and optical properties of poly(methyl methacrylate) (PMMA)/clay nanocomposites prepared with clay containing an organic modifier was investigated. Pristine sodium montmorillonite clay was modified using cocoamphodipropionate, which absorbs UVB in the 280–320 nm range, via ion exchange to enhance the compatibility between the clay platelets and the methyl methacrylate polymer matrix. PMMA/clay nanocomposites were synthesized via in situ free-radical polymerization. Three types of clay with various cation-exchange capacities (CEC) were used as inorganic layered materials in these organic–inorganic hybrid nanocomposites: CL42, CL120, and CL88 with CEC values of 116, 168, and 200 meq/100 g of clay, respectively. We characterized the effects of the organoclay dispersion on UV resistance, effectiveness as an O₂ gas barrier, thermal stability, and mechanical properties of PMMA/clay nanocomposites. Gas permeability analysis demonstrated the excellent gas barrier properties of the nanocomposites, consistent with the intercalated or exfoliated morphologies observed. The optical properties were assessed using UV–Visible spectroscopy, which revealed that these materials have good optical clarity, UV resistance, and scratch resistance. The effect of the dispersion capability of organoclay on the thermal properties of PMMA/clay nanocomposites was investigated by thermogravimetric analysis and differential scanning calorimetry; these analyses revealed excellent thermal stability of some of the modified clay nanocomposites.     

Molecular interaction and properties of poly(ether ether ketone)/liquid crystalline polymer blends incorporated with functionalized carbon nanotubes

Multi-walled carbon nanotubes (MWCNTs) were functionalized with a carboxyl group (-COOH) to achieve better interfacial adhesions with both phases of the poly(ether ether ketone) (PEEK) and liquid crystalline polymer (LCP) in their blend. These strong interfacial interactions among the functionalized MWCNTs, PEEK and LCP improved the mechanical properties of the polymer blend. Three different weight percentages (0.6%, 1.2% and 1.8%) of acid modified CNTs were used with PEEK-LCP blend, for the preparation of nanocomposites. In PEEK-LCP blend, the ratio of PEEK and LCP was maintained as 10:6 respectively. The tensile strength and modulus of the composites were improved by 51% and 73% respectively with the incorporation of only 1.2% of MWCNT-COOH as compared to the unfilled PEEK/LCP blend. Moreover, careful studies of the molecular interaction, morphological, dynamic mechanical and thermal properties confirmed that a better miscibility between PEEK and LCP had been constituted in the presence of MWCNT-COOH. Therefore, it was found that the functionalized MWCNTs not only played the traditional role as reinforcing filler, but also performed a novel role as a compatibilizer for the PEEK/LCP blends.     

Novel polyacrylonitrile/Na-MMT/silica nanocomposite: Co-incorporation of two different form nano materials into polymer matrix

Polyacrylonitrile (PAN)/Na-montmorillonite (Na-MMT)/SiO₂ nanocomposites were synthesized via in-situ emulsion polymerization. The X-ray diffraction (XRD) measurements and transmission electron microscopy (TEM) observations show that the Na-MMT layers were exfoliated in polymerization and the nano materials are well dispersed in the polymer matrix. The thermogravimetric analysis (TGA) suggests that co-incorporating Na-MMT and SiO₂ into the polymer matrix significantly enhances the thermal stability of the polymer. At same nano material loading, the PAN/Na-MMT/SiO₂ nanocomposites show superior thermal stability with respect to the PAN/Na-MMT and PAN/SiO₂ nanocomposites. The mechanical properties of the nanocomposites were also examined. It was found that the PAN/Na-MMT/SiO₂ nanocomposites exhibit considerably enhanced moduli compared with the PAN/Na-MMT and PAN/SiO₂ nanocomposites due to the synergistic reinforcing effect.