Nanofiller Loading Research Articles

Dielectric Relaxation Dynamics of Clay‐Containing Low‐Density polyethylene Blends and Nanocomposites

Series of clay‐containing nanocomposites have been prepared and investigated using frequency‐domain dielectric spectroscopy at different temperatures. Different matrix materials have been used: neat low‐density polyethylene (LDPE) with and without compatibilizer and co‐continuous blends of LDPE with two grades of polystyrene‐b‐poly(ethylene‐co‐butylene)‐b‐polystyrene (SEBS) copolymers. Two major relaxation modes were detected in the dielectric losses of all the nanocomposites and associated with Maxwell–Wagner–Sillars interfacial polarization and dipolar relaxation, respectively. Characteristic relaxation rates, activation energies, dielectric strength, and shape parameters of these relaxation mechanismes were calculated and discussed for the LDPE/clay nanocomposites. The addition of compatibilizer was found to slightly increase the dielectric loss of the nanocomposites while slowing the dynamics due to an improved dispersion. When combined with a high loading of nanofiller (15%), the compatibilizer addition led to low‐frequency dispersion. A new relaxation process was then observed for the nanocomposites with the blend matrix. Several speculations were made as to the origin of this phenomenon, all of which were related to the SEBS phase. POLYM. ENG. SCI., 60:968–978, 2020. © 2020 Society of Plastics Engineers

Interfacial interactions and interfacial polarization in polyazomethine/MWCNTs nanocomposites

We prepared the polyazomethine/MWCNTs nanocomposites varying in the nanofiller loading (from 0 to 1.5 wt%). Taking into account an upshift of the characteristic D and G bands of MWCNTs in the Raman spectrum of the nanocomposite, we confirmed the interfacial interactions between MWCNTs and polymer chains. When we studied the nanocomposites morphology, we concluded that both disentanglement and dispersion of MWCNTs in the polymer matrix are provided by interfacial interactions. Using broadband dielectric spectroscopy technique, we investigated the interfacial polarization in the nanocomposites. We found that this phenomenon is valuable for electrical conductivity of the nanocomposites with high MWCNTs loading, particularly, at high temperatures and low frequencies.

A polyamide membrane with tubular crumples incorporating carboxylated single-walled carbon nanotubes for high water flux

Membranes having excellent water permeability and high salt rejection are needed for developing nanofiltration technology. In the present work, a modified interfacial polymerization involving low-concentration monomers was utilized to synthesize an ultrathin polyamide (PA) layer. Carboxylated single-walled carbon nanotubes (COOH-SWCNT) were embedded into the ultrathin PA layer. The resultant additional molecular transportation pathways could reduce the trade-off effect. Besides, the morphology of ultrathin PA layer was sensitive to the presence of nanofillers, and contributed to a rougher surface of the thin film nanocomposite (TFN) membrane. As a result, the permeable area was increased, which is beneficial for water permeation. At the optimized COOH-SWCNT dosage of 0.001 wt%, even tubular crumples appeared on the fabricated membranes. Thereby, the membrane achieved an ultrahigh water permeance of 22.67 L·m−2·h−1·bar−1 while maintain a high rejection for divalent salt. For example, the rejection of Na2SO4 and MgSO4 were 95.69% and 90.03%, respectively. These excellent results were achieved using low loadings of nanofillers and under relatively low pressure (3.5 bar). The current work provides a feasible method to adjust the morphologies of NF membrane for improving its performance. And this is a promising approach due to its simplicity, and low consumptions of materials and energy.

Axial Alignment of Carbon Nanotubes on Fibers To Enable Highly Conductive Fabrics for Electromagnetic Interference Shielding.

Conductive coatings show great promise for next-generation electromagnetic interference (EMI) shielding challenges on textile; however, their stringent requirements for electrical conductivity are difficult to meet by conventional approaches of increasing the loading and homogeneity of conductive nanofillers. Here, the axial alignment of carbon nanotubes (CNTs) on fibers that were obtained by spontaneous capillary-driven self-assembly is shown on commercial cotton fabrics, and its great potential for EMI shielding is demonstrated. The aligned CNTs structurally optimize the conductive network on fabrics and yield an 81-fold increase in electrical conductivity per unit of CNT, compared with the disordered CNT microstructure. The high-efficiency electrical conductivity allows a several-micron-thick coating on insulating fabrics to endow an EMI shielding effectiveness of 21.5 dB in the X band and 20.8 dB in the Ku band, which meets the standard shielding requirement in commercial applications. It is among the minimum reported thicknesses for conductive nanocomposite coatings to date. Moreover, the coated fabrics with aligned CNTs possess a desirable stability upon bending, scratching, stripping, and even washing, which is attributed to the dense CNT packing in the aligned microarchitecture. This work presents the anisotropic structure on large areas by self-assembly, offering new opportunities for next-generation portable and wearable electronic devices.

Performance of Novel Engineered Materials from Epoxy Resin with Modified Epoxidized Natural Rubber and Nanocellulose or Nanosilica

Performance of new engineered material from epoxy resins with modified epoxidized natural rubber (ENR) and nanofillers were investigated. ENR from renewable natural crop resources is a type of green material with potential to partially substitute or replace and toughen petrochemical-based polymers. Nanocomposites (epoxy resin/ENR/fillers nanoparticles) were characterized with Fourier transform infrared spectroscopy (FTIR), dynamic light scattering (DLS), atomic force microscope (AFM), and scanning electron microscopy (SEM). Comparison of characterized and mechanical properties of nanofiller reinforced with both nanocellulose and nanosilica were studied. The nanocomposites were characterized for their mechanical properties (e.g., impact strength, tensile strength) and thermal degradation behaviour by thermal gravimetric analysis (TGA). Mechanical property investigation results show that, the impact strength of nanocomposites, can be improved by blending in ENR 50 mixed with nanofiller, relative to the baseline nanocomposite mixers. The nanofiller loading in epoxy composite showed the highest improvement in mechanical properties at 0.75 phr (parts per hundred of resin). Effects of accelerated weathering aging were evaluated, and the observed changes were larger with nanosilica than with nanocellulose filler. Here, the accelerated aging increase in tensile properties was found to be 10% after 14 days in both nanofillers, while the other mechanical properties did not change significantly. These nanocomposites are expected to have high wear rates limiting their service life.

Multifunctions of Polymer Nanocomposites: Environmental Remediation, Electromagnetic Interference Shielding, And Sensing Applications

AbstractPolymer nanocomposites (PNCs), i. e. nanofillers dispersed in a polymer matrix, have become a prominent area of current research promoted by rapid developments in the polymer science and nanotechnology. As a promising alternative to conventional composites which are reinforced with micro‐scale fillers, PNCs exhibit substantially improved overall performance and simplified processing at much lower nanofiller loadings. PNCs have great potentials for a broad range of applications, e. g. environmental remediation, energy storage/conversion, transportation, and national defense. In this regard, the most recent advances in PNCs for the environmental remediation, electromagnetic interference (EMI) shielding and sensing & actuation applications are presented. Challenges and perspectives of PNCs are also discussed.

Mechanical properties of graphene and nano-diamond reinforced ultra high molecular weight polyethylene

Nano-material reinforced ultra high molecular weight polyethylene (UHMWPE) composites are generally used as a joint replacement material. An investigation has been done on Hardness and 3-point bending of ultra high molecular weight polyethylene (UHMWPE) which was loaded with Nano-diamond (ND) and Graphene (Gr). In order to perform some mechanical tests a UTM test equipment and hardness test equipment were utilized. Due to the formation of a good molecular bonding, there is a significant increase in hardness from 51 HV for neat UHMWPE to 57 HV at 0.5 wt% ND loading of ND/UHMWPE nanocomposites and 54 HV at 0.3 wt% Gr loading of Gr/UHMWPE nanocomposites. At 0.5 wt% of Gr loading, the highest value of the flexural modulus (3750 N/mm2) is observed. When 0.5 wt% of Gr and 0.3 wt% of ND is added, then there is a significant increase in ultimate flexural strength and flexural modulus by loading of nano fillers. In this study the fabrication of ND/UHMWPE and Gr/UHMWPE nanocomposites exhibited good mechanical properties and they can be explode for total joint replacement.

Mechanical and electrical properties evaluation of PVA-carbon dot polymer nanocomposites

The main objective of this study is to investigate the effect of incorporationC-dots within polyvinyl alcohol (PVA) matrix for improving the mechanical and electrical properties. The thin films of these composites are prepared by the polymer intercalation solution casting method with various C-dot nanoparticles loading (0.5, 1.0, 1.5 and 2.0wt%) and compared properties with the pristine PVA. The fabricated nanomaterial composite films are characterized using well-known techniques such as Fourier transform infrared spectroscopy (FTIR) and X-ray diffractometer (XRD). From the analysis of FTIR and XRD results, it was estimated that the C-dot nanofiller has strong interaction with PVA polymer matrix. Further, from the mechanical properties estimation, it is observed the elastic modulus of 37 MPa increased by 98.05% when compared to pristine PVA. Tensile strength is found to increase with increase in filler concentration, 300% increase in tensile strength was observed for 2wt% filler loading compared to the pristine PVA. Electrical properties are strongly dependent on C-dot nanofiller loading, and the same was analyzed using LCR meter. It has been observed that the dielectric constant decreased with an increase in frequency. AC conductivity was estimated with respect to the frequency, the highest conductivity (7x10 -5 Sm -1 ) was observed for 1.5wt% of C-dot nanofiller PVA composite.

Competing charge trapping and percolation in core-shell single wall carbon nanotubes/ polyaniline nanostructured composites

Core-shell single wall carbon nanotube (SWCNT)/ polyaniline (PANI) nanocomposites were chemically synthesized and their structural, morphological, and dielectric properties were investigated as a function of the nanofiller content. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images confirm the core-shell nanostructural features of the composites. Broadband dielectric spectroscopy allows the detection of an interfacial dielectric relaxation mechanism which is quite dependent on the dispersion of nanoparticles into the semi-conducting polyaniline matrix. Furthermore, the relaxation process analysed through Kohlrausch-William-Watts (KWW) model, is found to take place at lower nanofiller loading but progressively fades away on increasing the amount of SWCNT, yielding relaxation spectra which gradually resemble that of a pure conductor. In addition, it is found that competing processes between electrical percolation and interfacial capacitance effects are inherently dependent on the carbon-filler content. Such a behaviour is ascribed to charge trapping and de-trapping phenomena occurring at core-shell interfaces. The possibility of tuning the composition of the nanocomposites in order to trigger an interplay between capacitance and dc-electrical conduction can be envisioned for their application in the next generation of organic-based supercapacitor or gate memory devices.

Surface topographical studies of glass fiber reinforced epoxy-ZnO nanocomposites

The objective of present research work is to investigate the surface morphology and surface microhardness of unidirectional E-glass fiber epoxy composites filled with varying amount of ZnO nanofiller content such as 1, 2, 3, 4 and 5 wt% respectively. ZnO nanofiller was added to the epoxy resin matrix in varying amount (wt%) using mechanical stirrer and followed by ultrasonication process. The laminate composites were fabricated using a compression molding press technique. Further, laminate composites were subjected to individual characterization and testing according to ASTM standards. The crystalline nature of ZnO nanofiller was studied using x-ray diffraction analysis (XRD) and surface morphology of ZnO nanofiller on the resin surface was examined by using a scanning electron microscope (SEM). The experimental test results revealed that addition of nanofiller content by 1, 2 and 3 wt% resulted in a gradual reduction of void fraction and thereafter increase in void fraction was observed with 4 and 5 wt% of ZnO loading. The surface microhardness results indicated a linear increment with increase in ZnO nanofiller loading from 1 to 5 wt%. Further, surface topography was studied with the help of atomic force microscopy (AFM), to obtain the surface roughness values. The surface roughness values increased with increase in ZnO wt% within the epoxy resin matrix. The results of the surface analysis of the fabricated composites indicate that at higher loading of ZnO nanofiller, there is formation of clusters and agglomerates of the nanofiller which reduces the nano-scale effects of the filler and nanofillers tend to behave as micro-fillers.

High electrical conductivity in polydimethylsiloxane composite with tailored graphene foam architecture

Graphene foam has huge potential applications in thermal management owing to their unique three-dimensional (3D) interconnected structure. It’s still a challenge to construct graphene foam architecture via facile and efficient method to reach superior property with low loading of nanofillers. Here, we report a polymer-template-assisted assembly strategy to develop 3D graphene architecture that is incorporated into polydimethylsiloxane (PDMS) composite with high electrical conductivity and thermal property. A free-standing foam structure has been assembled with graphene nanosheets, which was exfoliated in low-boiling-point chloroform with assistance of hyperbranched polyethylene as polymer stabilizer against aggregation via CH-π noncovalent interactions. The resultant graphene foam/PDMS composite exhibits high thermal conductivity of 0.22 W m−1 K−1 and high electrical conductivity of 9.1 × 10−3 S cm−1 at relatively low loading as 0.7 wt%, which is ascribed to the efficient transfer of charge carrier and thermal phonon along the graphene skeleton. This work demonstrates that the PDMS composite incorporated with graphene foam is a promising candidate for thermal interface materials with high electrical conductivity.

Mixed matrix membranes incorporated with sonication-assisted ZIF-8 nanofillers for hazardous wastewater treatment

Mixed matrix membranes (MMMs) provide a unique pathway to treat hazardous industrial effluents. MMMs containing zeolitic imidazolate framework-8 (ZIF-8) as filler in polydimethoxysilane (PDMS) matrix were synthesized. ZIF-8 was prepared using a modified recipe and characterized by different techniques to evaluate its morphology, thermal stability, surface area, pore volume, and other characteristics. The performance of membranes was evaluated for their application in industrial dye-stuff wastewater treatment and solvent-resistant nanofiltration. The results demonstrated that increase in the percentage of ZIF-8 loading in PDMS led to simultaneous increase in the solvent permeability as well as solute rejection from wastewater. The permeability of MMMs increased up to 32% as compared with neat PDMS membrane. The organic dye rejection was achieved more than 87% with MMMs incorporated with 20% loading of nanofillers. Rejection of MMMs was 22% higher than that of unfilled PDMS membrane due to the effect of reduced polymer swelling and size exclusion of the nanofillers. Membrane swelling tests with toluene and isopropanol demonstrated that nanofiller amount has inverse relation with membrane swelling, which implied that nanofillers were in good interaction with polymer and allowed defect free membranes with higher solute rejections and reduced membrane swelling.

Study of Electromagnetic Properties of Fabricated NiFe2O4/Polyurethane Nanocomposites

ABSTRACTNickel ferrite loaded (NiFe2O4) segmented polyurethane (SPU) nanocomposites prepared by melt mixing method using microcompounder at temperature 185 °C in recirculation mode to ensure proper dispersion and distribution of nanoparticles at optimized residency time of 5 min. Three different weight percentages of nanocomposites (3, 5, and 10 wt %) was prepared and studied the electromagnetic property of nanocomposites obtained from complex permittivity and permeability. The effect of nanofiller (NiFe2O4) has been studied to assess their thermal properties using thermogravimetric analysis, differential scanning calorimetry, and thermomechanical analysis. The nanocomposites (NiFe2O4/SPU) have further been studied using FE‐SEM, and the micrographs show embedded NiFe2O4 filler uniformly dispersed in SPU matrix without agglomeration (size 20–40 nm). It is also evident that further loading of nanofiller resulted in saturation effect yielding no applicable change in thermal behavior and revealed lesser melting enthalpy due to the coalescence of the nanofillers. X‐ray diffraction and vibrating sample magnetometer also support the formation of the nanocomposite. The electric and magnetic properties of NiFe2O4 incorporated nanocomposite (NiFe2O4/SPU) may have potential application in microwave absorption. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48645.

The coupling effect of interfacial traps and molecular motion on the electrical breakdown in polyethylene nanocomposites

Low-density polyethylene (LDPE) based nanocomposites are capable of suppressing the accumulation of space charges and enhancing the resistivity and electrical breakdown strength, which are beneficial for the performance and reliability of high voltage direct current power cables. Incorporating nanofillers into polymers can form interfacial regions inside and affect both the trap distribution and molecular motion characteristics, resulting in changes in the dielectric properties of polymer nanocomposites. To unravel the influencing mechanism of interfacial traps and molecular motion on the dc electrical breakdown strength, we investigate the dc electrical breakdown properties of LDPE/Al2O3 nanocomposites as a function of nanofiller loading, pressure, ramping rate of voltage, and sample thickness by experiments and simulations of the charge transport and molecular displacement modulated electrical breakdown. Experimental and simulation results are consistent and show that dc electrical breakdown strength increases firstly and then decreases with the increase of nanofiller loading, increases monotonically with increasing pressure and ramping rate of voltage, and decreases with the increase in sample thickness, obeying an inverse power law. It is indicated that the dc electrical breakdown of LDPE/Al2O3 nanocomposites is triggered by the local current and energy multiplication caused by charge carriers jumping over deep traps when they gain sufficient energy in the enlarged free volume via molecular displacement. It is concluded that both the increase in deep trap energy and the restraint of the motion dynamics of molecular chains with occupied deep traps can enhance the dc electrical breakdown strength of LDPE/Al2O3 nanocomposites.

Effect of rGO:MWCNTs ratio on electrical conductivity of polyazomethine/rGO:MWCNTs nanocomposites

Using solution blending method, we produced nanocomposites based on polyazomethine (PAZ) loaded with hybrid carbon nanofillers. The nanofillers comprised reduced graphene oxide (rGO) and multi-walled carbon nanotubes (MWCNTs). The total nanofiller loading was equal to 1 wt% while the rGO:MWCNTs ratio varied as follows: 100:0, 75:25, 50:50, 25:75, and 0:100 wt%: wt%. The complex dielectric permittivity data obtained with a broadband dielectric spectrometer were used to analyze electrical conductivity of the nanocomposites in wide ranges of frequency and temperature. Electrical conductivity was found to increase with increasing MWCNTs portion and its maximum value was achieved when the nanofiller contained the MWCNTs nanoparticles exclusively. We extracted the electrical conductivity components, dc conductivity σdc and ac conductivity σac, and analyzed their behavior as function of frequency and temperature. The temperature dependences of σac were described with the Arrhenius equation, whereas its frequency dependences were characterized with a power function. For explaining the σac behavior, the correlated barrier hopping mechanism was accepted. Interfacial interactions between the hybrid nanofillers and the polymer matrix (the Maxwell-Wagner-Sillars effect) were detected. It was found to be strongly pronounced in the nanocomposites with high portion of MWCNTs in the hybrid fillers.

Improvements on Mechanical Property and Microstructure of Cementitious Composite Incorporated with Silica Fume and Carbon Nanotube

Nano-size fillers (ultrafine silica fume (USF) or/and multi-walled carbon nanotube (MWCT)) were incorporated into cement matrix to fabricate nano-fillers reinforced cementitious materials (NFRCs) with surfactant ultrasonic dispersion and subsequently mix cast process. The flexural and compressive strengths of four groups NFRCs with varied nano-filler loading were comprehensively investigated. Results show, there are positive effects on the flexural and compressive strength of NFRCs with nano-fillers loading, especially when USF and MWCT are incorporated simultaneously, and the correspondent maximal flexural and compressive strength can increase by above 17%, 28% with respect to the baseline, respectively. The pozzolan infilling effect of USF and the crack-bridging effect of dispersed MWCT result in the dense and integrated network microstructures of cured NFRC.

Idiosyncratic cellulose acetate nanocomposite membranes: synthesis and performance control study for desalination

ABSTRACT In order to enhance the characteristic performance of cellulose acetate (CA) membranes, a novel nanofiller synergy is adopted herein for desalination purpose. Activated zinc oxide and aero-silica synergy in seven different ratio based combinations were introduced into CA matrix adopting solution mixing technique. The functionalized nanofillers loading impact on membranes surface texture, crystalline structural difference, functional groups presence, thermal decomposition and phase transition temperatures were scrutinized. The sole membranes were practically employed to determine salts (NaCl and MgCl2) rejection tested by dead-end filtration system. Time dependent flux rate and fouling study were performed to decide the reuseability of nanocomposite membranes. The results validate a remarkable improvement by idiosyncratically synthesized nanocomposite membranes.

Graphene type dependence of carbon nanotubes/graphene nanoplatelets polyurethane hybrid nanocomposites: Micromechanical modeling and mechanical properties

Micromechanical modeling and mechanical properties of polyurethane (PU) hybrid nanocomposite foams with multi-walled carbon nanotubes (MWCNTs) and graphene nanoplatelets (GNPs) were investigated by means of tensile strength, hardness, impact strength and modified Halpin–Tsai equation. Three types of GNPs, with varied flake sizes and specific surface areas (SSA) were utilized to study the effect of GNP types on the synergistic effect of MWCNT/GNP hybrid nanofillers. The results indicate a remarkable synergetic effect between MWCNTs and GNP-1.5 (1:1) with a flake size of 1.5 μm and a higher SSA (750 m2/g), which tensile strength of PU was improved by 43% as compared to 19% for PU/MWCNTs and 17% for PU/GNP-1.5 at 0.25 wt% nanofiller loadings. The synergy was successfully predicted using a unit cell modeling, which the calculated values agree with the experimental results.

Graphite/UPE Nanocomposite: Transport, Thermal, Mechanical and Viscoelastic Properties

This chapter presents the preparation and characterization of some unique properties of nanocomposites by dispersing graphite flakes in commercial unsaturated polyester (UPE) matrix. The composite was prepared by a novel method with the use of solvent swelling technique. Three different specimens of UPE/graphite nanocomposites were fabricated with addition of 1, 2 and 3 wt% of graphite flakes. Except mechanical, viscoelastic and thermo gravimetric properties, transport properties like electrical conductivity, thermal conductivity and water transport properties were studied for the first time. Graphite flakes propose enhanced properties to the composites suggesting homogeneous distribution of the nanofiller in the matrix and strong interaction with the matrix. 2wt% nanofiller loading showed superior essential characteristics and after that the properties reduced may be due to the nucleating tendency of the nanofiller particles. The XRD pattern showed the compatibility of the graphite flakes by introducing a peak around 26.550 in the nanocomposites. SEM Properties are also in agreement with the compatibility. Nanocomposite with 2wt% graphite also showed remarkable enhancement in transport, mechanical, viscoelastic and thermo gravimetric properties. So by introduction of a small quantity of graphite endow the new class of multiphase nanocomposites with inimitable structure and tremendous application.

The effect of filler loading ratios and moisture on DC conductivity and space charge behaviour of SiO2 and hBN filled epoxy nanocomposites

Nanocomposites that exhibit good insulation properties have already attracted a variety of research and their electrical properties are believed to be related to charge dynamics in bulk of materials. However, it is still unclear on how nanofiller loading ratios, surface treatment and resultant changes in morphology will influence the charge dynamics of nanocomposites. In this paper, we have clearly mentioned the influence of adding nanoparticles into epoxy resins and the characteristics of the movement of charges in the materials based on combining analysis on morphology, DC conductivity and space charge measurements. The presence of spherical nanoparticles (SiO2) introduced additional traps in bulk, which impaired the charge injection and reduced the mobility of charge carriers in samples of low filler loading ratios (e.g. 0.5 wt%). However, in silica-based samples of higher filler loadings, more nanoparticles further caused a higher density of traps, which resulted in lower average distance between arbitrary traps/inter-particle surface distances and thus charge carriers required less energy when moving from one to another by hopping or the quantum tunnelling mechanism. The surface treatment of SiO2 particles introduced deep traps which helped the separation of particles or related traps, and to some extent restricted the transport of charge carriers. In addition, hBN particles seem to act as barriers to charge injection and movement due to the layered structures and large numbers of resultant shallow traps in bulk. In terms of the moisture effect, the presence of water led to an obvious increase in charge injection and mobility, and resulted in the higher mobility of charge carriers in both base materials and within traps/particles of nanocomposites. The existence of water shells around spherical particles could contribute to a higher probability of the quantum tunnelling process and the formation of conductive percolation channels.