Filled Polymer Nanocomposites Research Articles

Fluoride ion encapsulated polyhedral oligomeric silsesquioxane: A novel filler for polymer nanocomposites with enhanced dielectric constant and reduced dielectric loss

Polymer dielectrics have been considered as an ideal choice for preparation of advanced power and electronic systems as their good comprehensive performances. However, it remains a challenge to obtain polymer dielectrics with high dielectric constant (εr), low dielectric loss (tan δ) and high temperature capability. Although adding high permittivity inorganic nanofillers has become a promising approach to improve the εr of polymers, it usually causes the adverse increment tan δ. Herein, we demonstrate that fluoride ion encapsulated polyhedral oligomeric silsesquioxane (POSS@F−) can be regarded as a novel filler to enhance the εr and reduce the tan δ of poly(2,6-dimethyl-1,4-phenylene oxide) (PPO) simultaneously. Compared with the pristine PPO, the εr of PPO/POSS@F− composite can be enhanced from 2.81 to 5.31, while its tan δ is still relatively low (0.0011 at 1 kHz). Meanwhile, the breakdown strength of PPO can also be slightly reinforced from 334.9 kV/mm to 394.0 kV/mm. Owing to the good thermal properties of PPO and POSS@F−, these composites exhibit good dielectric properties and improved dimension stability at high temperature. We believe that these results are particularly important for the preparation of advanced dielectric materials for desirable applications.

Toughening Effect of Rodlike Cellulose Nanocrystals in Epoxy Adhesive

Epoxy structural adhesives have been used extensively in the automotive and aerospace industries to bond assembly parts. Much effort has been devoted to enhancing the mechanical properties of epoxy resin by incorporating fillers. Among a variety of fillers investigated for this purpose, nanocelluloses are regarded as a promising type of emerging green filler material because of their excellent mechanical and physicochemical properties. Indeed, nanocelluloses have been used as a filler for polymer nanocomposites. However, the toughening and reinforcing effects of nanocelluloses on rigid epoxy adhesives have not yet been fully revealed, particularly from the perspective of adhesive bonded joints. Here we report that epoxy adhesive containing cellulose nanocrystal (CNC) aggregates produced using a solvent-free ball milling method achieves drastically improved adhesive strength and fracture toughness compared with that of the reference adhesive without CNCs. The epoxy adhesive containing CNC aggregates exhibi...

Chemically bonding BaTiO3 nanoparticles in highly filled polymer nanocomposites for greatly enhanced dielectric properties

BaTiO3 nanoparticles with extremely high loading are chemically bonded with silicone rubber via “thiol–ene click”, leading to superior dielectric properties.

Effect of the shear field on the conductive percolated network formation in a nanoparticle filled polymer nanocomposites

ABSTRACT It is very important to improve the electrical conductivity of polymer nanocomposites (PNCs) which can widen their application. In this work, a coarse-grained molecular dynamics simulation is adopted to investigate the effect of the nanoparticle (NP) functionalization on the formation of the conductive network under the quiescent state or under the shear field, which is denoted by the conductive probability. First, the dispersion state of NPs is characterized which varies from the contact aggregation, the relatively uniform dispersion to the local bridging structure via one polymer layer with the increase of the functionalization degree . Corresponding to it, the percolation threshold of PNCs exhibits a continuous decrease with the increase of under the quiescent state which reflects the high conductive probability. However, the percolation threshold shows a weak increase under the shear field. Thus, the decides whether the conductive probability increases or decreases under the shear field. The smallest change in the percolation threshold appears at the moderate which reflects the highest conductive stability. Especially, even though the dispersion state of NPs is different for , the percolation threshold is similar under the shear field. The connection mode among NPs is considered to determine the formation of the conductive network. In summary, this work can help to understand how the NP functionalization affects the electrical conductivity of PNCs.

Polyethylene/graphene oxide composites toward multifunctional active packaging films

The addition of nanoparticles into a polymer can produce multifunctional films having not only gas barrier and antimicrobial characteristics for active packaging, but also improved mechanical and thermal behaviours. Among the different nanoparticles, graphene oxide (GO) has the potential to develope active polymers due to its layer structure and biocide property. In this study, linear low density polyethylene (LLDPE) was melt mixed with GO nanoparticles having different oxidation and exfoliation degrees. Our results shown that the elastic modulus of LLDPE composites increased with the amount of GO, and by using highly oxidated GO this reinforcement effect was observed without reducing the elongation at break. The thermal stability of the composites under either inert and oxygen atmosphere also increased as compared with the pure matrix. Regarding the barrier properties, the oxygen permeability of the composites depended on the amount and kind of filler, and while GO with low oxidation increased dramatically the permeability of the polymer, highly oxidated GO decreased this value. These results were explained through the Felske model. Water vapor permeation otherwise was not affected by the presence of the nanofillers. The LLDPE/GO nanocomposites further presented antimicrobial behaviour against Salmonella Typhi and Listeria monocytogenes strains. These results confirmed that GO can be designed as an active filler in polymer nanocomposites for packaging applications.

Reinforcement of Polymer/2D Filler Nanocomposites: Basic Postulates

It has been shown that almost every theoretical model known to date allows for correctly describing the properties of polymer nanocomposites on the condition that the real not nominal characteristics of their components are used. These real characteristics are always related to the formation of the interfacial regions in the mentioned nanomaterials. This means that the efficiency of the filler in polymer nanocomposites is controlled by its ability to generate interfacial regions.

Thermal behavior of PC-ABS based graphene filled polymer nanocomposite synthesized by FDM process

Abstract Property enhancement of polymers could be achieved through blending of two or more polymers and via addition of filler materials to meet the application requirements. In the present investigation Polycarbonate (PC) and Acrylonitrile Butadiene Styrene (ABS), the two polymers were blended together and Graphene platelets as nanofiller was added in the ratio of 0.2, 0.4, 0.6 and 0.8 wt% respectively. Polymer blend and graphene platelets were mixed at appropriate temperature and extruded out in the form of filament of 1.75 mm diameter. Filament was used as a feed material for Fused Deposition Modelling (FDM) to develop the test samples. The nanocomposites developed using FDM were subjected to differential Scanning Calorimetry (DSC) and Thermogravimetric Analysis (TGA) to study the effect of graphene platelets. Addition of graphene platelets resulted in significant increase in Young's modulus with highest value of 4.038 GPa obtained for nanocomposite with 0.8% graphene content. Thermal analysis showed that addition of graphene platelets increases the glass transition temperature and reduces the mass with increase in temperature.

Electric field induced tunable memristive characteristics of exfoliated graphene oxide embedded polymer nanocomposites

Resistive switching properties of layered graphene oxides (GOs) filled polymer nanocomposites (PNCs) have received tremendous attention in the field of memory devices. Herein, we report highly stable write-once-read-many-times (WORM) resistive switching properties of exfoliated GOs embedded poly(methyl methacrylate) (PMMA) thin films. The WORM characteristics of the PNC devices have been studied by varying the active layer thickness and the content of GO nanofillers. A disrupted carbon network of GOs enables defect states that act as an energy barrier for carriers and the charge transport through the PNC devices is blocked at a lower electric field. At an elevated electric field, GO sheets embedded PMMA offers percolation pathways for electron transfer, thereby making the composites electrically more conductive. The set voltage (VSET) decreases with a decrease in the active layer thickness, whereas VSET increases with a decrease in the GOs content within PNC devices. For a fixed compliance current (∼1 μA), highest ION/IOFF ratio ∼104 at 1.87 V has been achieved for the PNCs device spin-coated at 9000 rpm with 0.1 wt. % GOs content. The stability of the devices has been confirmed through retention test up to 104 s. In addition, the J-V curves are fitted and an appropriate conduction mechanism is proposed.

Thermal conductivity of highly filled polymer nanocomposites

A model is developed for the effective thermal conductivity of composites with polymer matrices reinforced with randomly distributed micro- and nano-particles. The model takes into account formation of infinite conducting paths and finite aggregates of particles on the one hand, and thermal barriers at the interfaces between the matrix and filler, on the other. Material parameters are determined by matching observations on a number of composites with ceramic and carbon fillers. The intensity of thermal barriers is evaluated by means of the Kapitza radius. Comparison of experimental data with results of simulation demonstrate that this parameter is determined by filler only, and it is weakly affected by the matrix material.

Synthesis and characterization of porous clay-organic heterostructures

This work describes the synthesis and characterization of porous clay-organic heterostructures. The silylation of organically modified clay minerals by a phenyl-bridged silica precursor can create a silica network between the clay layers while simultaneously an exfoliated heterostructure is achieved. Subsequent thermal treatment up to 350 °C removes the aliphatic moieties of the heterostructure and subsequently high surface area is obtained, while a high amount of phenylene groups are still remained trapped in the silica network. This intriguing phenyl/heterostructure possesses a hydrophobic character and accessible surface areas alongside the presence of the phenylene groups embedded in the silica network making this novel material very attractive for potential use in diverse functional applications in catalysis, absorption and as filler in polymer nanocomposites.

High dielectric and breakdown properties achieved in ternary BaTiO3/MXene/PVDF nanocomposites with low-concentration fillers from enhanced interface polarization

Although high permittivity is achieved in barium titanate (BT) filled polymer nanocomposites, severely reduced insulation and breakdown properties are frequently found due to overload and agglomeration of BT nanoparticles with ultrahigh specific area. To simultaneously realize high permittivity and breakdown strength, in this work, unfunctionalized 2D Ti3C2 MXene nanosheets with 2 wt% weight concentration were introduced to prepare ternary BT/MXene/polymer nanocomposites by solution cast process. Employing low-concentration conductive MXene instead of high-concentration ferroelectric BT could lead to significant improvement of permittivity of ternary composites, ascribed to remarkably increased interface types and enhanced interface polarization. In comparison to binary BT/polymer composites, ternary composites could have slightly improved dielectric loss and conductivity as well as gracefully reduced breakdown strength, attributed to finely retained high interface compatibility and filler dispersion. Ternary composite containing 8 wt% BT and 2 wt% MXene had a permittivity of 77, loss of 0.15 at 100 Hz and breakdown strength of 220 MV m−1. This work might open the door to large-scale fabrication of promising composites with high permittivity and breakdown strength under low filler loading (~ 10 wt%).

Усиление нанокомпозитов полимер/2D-нанонаполнитель: базовые постулаты

AbstractIt has been shown that almost every theoretical model known to date allows for correctly describing the properties of polymer nanocomposites on the condition that the real not nominal characteristics of their components are used. These real characteristics are always related to the formation of the interfacial regions in the mentioned nanomaterials. This means that the efficiency of the filler in polymer nanocomposites is controlled by its ability to generate interfacial regions.

EFFECT OF THE NANOFILLER SHAPE ON THE CONDUCTIVE NETWORK FORMATION OF POLYMER NANOCOMPOSITES VIA A COARSE-GRAINED SIMULATION

ABSTRACT It is very important to improve the electrical conductivity of polymer nanocomposites, which can widen their application. The effect of the nanofiller shape on the relationship between the nanofiller microstructure and the conductive probability of the nanofiller filled polymer nanocomposites (PNCs) has been investigated in detail by employing a coarse-grained molecular dynamics simulation. Four kinds of nanofiller shapes are considered: rod filler, Y filler, X filler, and sphere filler. First, the mean square radius of gyration gradually decreases from rod filler, Y filler, X filler, to sphere filler, which reflects the highest aspect ratio for rod filler. Meanwhile, the dispersion state of the nanofiller is relatively uniform in the matrix. The conductive probability (denoted by the formation probability of the conductive network) is adopted to stand for the conductive property. The results show that the conductive probability gradually decreases from rod filler, Y filler, X filler, to sphere filler, which is attributed to their gradually decreased size. In summary, the nanofiller shape affects the electric conductive property of PNCs.

AC and DC electrical behavior of MWCNT/epoxy nanocomposite near percolation threshold: Equivalent circuits and percolation limits

This study attempts to comprehensively investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the AC and DC electrical conductivity of epoxy nanocomposites. The samples (0.2, 0.3, and 0.5 wt. % MWCNT) were produced using a combination of ultrason and shear mixing methods. DC measurements were performed by continuous measurement of the current-voltage response and the results were analyzed via a numerical percolation approach, while for the AC behavior, the frequency response was studied by analyzing phase difference and impedance in the 10 Hz to 0.2 MHz frequency range. The results showed that the dielectric parameters, including relative permittivity, impedance phase, and magnitude, present completely different behaviors for the frequency range and MWCNT weight fractions studied. To better understand the nanocomposites electrical behavior, equivalent electric circuits were also built for both DC and AC modes. The DC equivalent networks were developed based on the current-voltage curves, while the AC equivalent circuits were proposed by using an optimization problem according to the impedance magnitude and phase at different frequencies. The obtained equivalent electrical circuits were found to be highly useful tools to understand the physical mechanisms involved in MWCNT filled polymer nanocomposites.

Significantly Elevated Dielectric and Energy Storage Traits in Boron Nitride Filled Polymer Nano-composites with Topological Structure

Interface induced polarization has a prominent influence on dielectric properties of 0–3 type polymer based composites containing Si-based semi-conductors. The disadvantages of composites were higher dielectric loss, lower breakdown strength and energy storage density, although higher permittivity was achieved. In this work, dielectric, conductive, breakdown and energy storage properties of four nano-composites have been researched. Based on the cooperation of fluoropolymer/alpha-SiC layer and fluoropolymer/hexagonal-BN layer, it was confirmed constructing the heterogeneous layer-by-layer composite structure rather than homogeneous mono-layer structure could significantly reduce dielectric loss, promote breakdown strength and increase energy storage density. The former worked for a larger dielectric response and the latter layer acted as a robust barrier of charge carrier transfer. The best nano-composite could possess a permittivity of 43@100 Hz (~ 3.3 times of polymer), loss of 0.07@100 Hz (~ 37% of polymer), discharged energy density of 2.23 J/cm3@249 kV/cm (~ 10 times of polymer) and discharged energy efficiency of 54%@249 kV/cm (~ 5 times of polymer). This work might enlighten a facile route to achieve the promising high energy storage composite dielectrics by constructing the layer-by-layer topological structure.

Template-Free Synthesis of Aligned Polyaniline Nanorods/Tubes and Copper/Copper Hydroxide Nanowires for Application as Fillers in Polymer Nanocomposites

Aligned polyaniline nanorods were synthesized in the presence of salicylic acid. Nanorods and nanotubes were also formed in the presence of camphorsulfonic acid (CSA) and para-toluenesulfonic acid (pTSA). Electrical conductivity measurements showed that the aligned nanorods had better electrical conductivity than the non-aligned nanostructures. Nanospheres were also observed in some cases. The formation of elongated nanostructures or spheres depended on the aniline monomer to surfactant molar ratio. This method in which nanostructures are formed using soft templates is often referred to as the template-free approach. Our success motivated us to explore the feasibility of obtaining similar metallic nanostructures without the use of a template. We successfully synthesized copper and copper hydroxide nanowires. While the copper nanowires formed as a mesh, the copper hydroxide nanowires formed as winding bundles. Upon switching the order in which the reactants were added, copper hydroxide nanoribbons were formed instead of bundles. Characterization of these nanostructures was done using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Transmission Electron Microscopy (TEM), Fourier Transform Infrared Spectroscopy (FTIR) and the Four-point probe to measure electrical conductivity. Both metallic and organic nanowires that are fabricated by template-free methods are potential candidates for use as fillers in polymer nanocomposites. Polymer nanocomposites are found to be used in many advanced modern applications such as thermal interface materials in electronic devices which continue to be miniaturized, aerospace engineering where lightweight and robustness are important, sensors, medicine and catalytic activity.

A three-dimensional multilayer graphene web for polymer nanocomposites with exceptional transport properties and fracture resistance

A CVD-grown high-density 3D multilayer graphene web (MGW) is used as the filler for polymer nanocomposites, delivering exceptional electrical and thermal conductivities with outstanding fracture toughness.

The effective complex permittivity stability in filled polymer nanocomposites studied above the glass transition temperature

The temperature effecton the dielectric response of nanocomposite at low frequencies range is reported. The investigated samples are formed by a semi-crystalline ethylene-co-butyl acrylate (EBA) polymer filled with three concentrations of the dispersed conducting carbon black (CB) nanoparticles. The temperature dependence of the complex permittivity has been analyzedabove the glass transition temperature of the neat polymer matrix Tg=-75°C. For all CB concentrations, the dielectric spectra follow a same trend in frequency range 100-106Hz. More interestingly, the stability of the effective complex permittivity ɛ=ɛ' -iɛ'' with the temperature range of 10-70°C is explored. While the imaginary part of the complex permittivity ɛ'' exhibits a slight decreasewith temperature, the real part ɛ' shows a significant reduction especially for high loading samples. The observed dielectric response may be related to the breakup of the three-dimensional structurenetwork formed by the aggregation of CB particles causing change at the interfaceEBA-CB.This interface is estimated bythe volume fraction of constrained polymer chain according to loss tangent data of dynamic mechanical analysis.

Monte Carlo modelling of percolation and conductivity in carbon filled polymer nanocomposites

Conducting polymer composites are attractive alternatives for applications such as electromagnetic shielding in which metals are conventionally used. They have unique advantages like light weight, ease of processing and good strength to weight ratio. This makes them economically viable especially in industries like avionics where weight is an important criterion. However, a major challenge in using conducting polymer composites in many of the applications is its limited conductivity. Even though many models exist to describe the conductivity of the composites at the macro level taking into account the interparticle conductivity, very few studies are conducted to understand the conductivity of the composites directly from basic principles. In this study, Monte Carlo (MC) simulations are carried out to study the conductivity in such composites. The results obtained using the MC model showed good agreement with the Mamunya model and the experimental measurements. The effect of various parameters like filler diameter and filler conductivity on the final composite conductivity is studied for spherical and fibrous carbon fillers in silicone rubber. The method can be easily adopted for any other filler-polymer combination and can also be used as a predictive tool for designing simple composites of required electrical properties.

Controlling the electrical conductive network formation in nanorod filled polymer nanocomposites by tuning nanorod stiffness.

In this work, by employing a coarse-grained molecular dynamics simulation, we have investigated the effect of the nanorod (NR) stiffness on the relationship between the NR microstructure and the conductive probability of NR filled polymer nanocomposites (PNCs) under the quiescent state and under the shear field. The conductive probability of PNCs is gradually enhanced with the increase of NR stiffness in the quiescent state; however, it first increases and then decreases under the shear field. As a result, the largest conductive probability appears at moderate NR stiffness, which results from the competition between the improved effective aspect ratio of the NR and the breakage of the conductive network. Meanwhile, compared with in the quiescent state, under the shear field the decrease or the increase of the conductive probability depends on the NR stiffness. At low NR stiffness, the increase of the effective aspect ratio of NR enhances the conductive probability, while at high NR stiffness, the breakage of the conductive network reduces the conductive probability. For flexible NRs, the conductive probability first increases and then decreases with increasing the shear rate. The maximum effective aspect ratio of NRs appears at the moderate shear rate, which is consistent with the conductive probability. In summary, this work presents some further understanding about how NR stiffness affects the electric conductive properties of PNCs under the shear field.