Dielectric Loss Of Composites Research Articles

The hierarchical layer with dynamic imine bonds on carbon fiber surface to simultaneously improve interface and electromagnetic shielding properties of carbon fiber reinforced thermoplastic composites

Constructing surface hierarchical layer is regarded as an effective surface modification of carbon fibers (CFs) to enhance their composites mechanical properties. However, this method usually deteriorates the intrinsic properties of CF and the hierarchical layer is not fully compatible with thermal processing of the polymer. Here, a novel hierarchical layer consisting of polydopamine, polyethyleneimine and multi-walled carbon nanotubes without damages to CF was successfully decorated on CF surface (CNT@PP-CF) for simultaneously enhancing the mechanical and the electromagnetic interference (EMI) shielding properties of CF reinforced polyamide 66 (PA66) composite. The CNT@PP hierarchical layer with dynamic imine bonds enhanced the interfacial wettability and bonding between CF and PA66 during thermal processing. Compared with that of untreated-CF, the interfacial shear strength and tensile strength of CNT@PP-CF/PA66 composite were increased by 52.3% and 19.2%, respectively. Meanwhile, the EMI shielding performance was enhanced by 89.6%. This improvement would be ascribed to the dynamic imine polar groups and heterogeneous interfaces in the hierarchical layers which enhanced the conductive and dielectric losses of composites. Our research provided a novel approach based on dynamic covalent bond exchanges to achieve the functional and structural integration of CF reinforced thermoplastic resin composites.

Electrical Tree Characteristics of Epoxy Resin/Aln Nanocomposites in LN2 With Repetitive Nanosecond Pulse Voltage

Under the action of nanosecond pulse voltage, the insulation material is prone to partial discharge, which induces the generation of electrical trees and insulation failure. The epoxy resin/aluminum nitride (AlN) nanocomposites are developed to suppress the development of electrical treeing for cryogenic insulation of high-temperature superconducting power equipment. The effects of the content of aluminum nitride material on the relative permittivity and dielectric loss of composites were studied, as well as the growth characteristics of electrical treeing at liquid nitrogen temperature. The findings reveal that the samples with the AlN content of 3 wt% have the highest relative permittivity, rising by 15%, but nanoparticle doping has no significant effect on the dielectric loss of composites. Furthermore, the right amount of AlN nanoparticle doping will improve the electrical treeing resistance of epoxy resin and the insulation properties of composites.

Dielectric and AC Breakdown Properties of SiO2/MMT/LDPE Micro–Nano Composites

Low-density polyethylene (LDPE) is an important thermoplastic material which can be made into films, containers, wires, cables, etc. It is highly valued in the fields of packaging, medicine, and health, as well as cables. The method of improving the dielectric property of materials by blending LDPE with inorganic particles as filler has been paid much attention by researchers. In this paper, low-density polyethylene is used as the matrix, and montmorillonite (MMT) particles and silica (SiO2) particles are selected as micro and nano fillers, respectively. In changing the order of adding two kinds of particles, a total of five composite materials were prepared. The crystallization behavior and crystallinity of five kinds of composites were observed, the εr and tanδ changes of each material were investigated with frequency and temperature, and the power frequency (50 Hz) AC breakdown performance of materials were measured. The differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results show that the crystallinity of the composites is higher than that of LDPE. Experimental data of dielectric frequency spectra show that the dielectric constants of micro–nano composites and composites with added MMT particles are lower than LDPE, the dielectric loss of composites can be improved by adding MMT particles. The experimental data of dielectric temperature spectra show that the permittivity of SiO2-MMT/LDPE is still at a low level under the condition of 20~100 °C. In terms of breakdown field strength, the SiO2/LDPE composite material increased by about 17% compared with the matrix LDPE, and the breakdown field strength of the materials SiO2-MMT/LDPE and MMT-SiO2/LDPE increased by about 6.8% and 4.6%, respectively.

MOF and GNS work synergistically for low-k materials with higher thermal conductivity

In this work, the low dielectric constant composites with higher thermal conductivity are prepared, combining ZIF-8 insulation and graphite nanosheets (GNS) thermal conductivity via designing suitable configuration and synergistically reacting in epoxy resin matrix. It demonstrated that ZIF-8@GNS/EP (ZGNS/EP) composites have decreased by 26.4% in low dielectric constant and increased by 300.7% in thermal conductivity compared with neat EP. The dielectric loss of composites is always less than 0.033(102–107 Hz). Simultaneously, the tensile strength of the 0.5 wt% ZGNS/EP composite is increased by 71.1% than before. Overall, this work presents new ideal to prepare low dielectric constant materials, which also possess low loss and excellent thermal conductivity.

Modified BaTiO3/PVDF/Ni composites with high dielectric constant and low dielectric loss

Low dielectric properties of BaTiO3/PVDF composites limit its application in modern microelectronics and high energy storage. In this work, three-phase composites with high dielectric properties were prepared based on the surface modification of BaTiO3(BT) ceramic. The results show that, after modification of BT, the dielectric constant of the BT/PVDF composite increased by 44%, and the dielectric loss decreased by 20% at 100Hz. Nickel powder was added to the modified composites for increasing dielectric constant, when the addition of nickel powder was 20%, the dielectric constant of composites was up to 441 and the dielectric loss of composite was only 0.057.

Effects of M220 on the crystal structure and dielectric properities of P(VDF-HFP)

Polymer composites with high energy density are fabricated through incorporation of core–shell structure M220 into P(VDF-HFP) matrix by solution blending. The M220 is core–shell structure, and the ratio of core to shell is 7:3, the outer shell is PMMA, and the inner shell is interpolymer of butyl methacrylate and amyl methacrylate. The structure and properties of the samples are characterized by scanning electron microscopy (SEM), polarizing microscope (POM), FTIR, XRD, DSC and TG. Moreover, breakdown strength, dielectric properties and hysteresis loops are measured to indicate the electrical performance of the composites. The results show that the addition of M220 makes the crystallinity, melting temperature and thermostability dropped. In addition, the breakdown strength and the discharge efficiency of composite films improved substantially while the dielectric constant and dielectric loss of composites both decreased with the introduction of M220. Compared the effects of M220 with PMMA as fillers on discharge efficiency, the inhibition effect of PMMA on the crystallization of P(VDF-HFP) is more obvious for the discharge efficiency of the materials.

Excellent energy storage performance and thermal property of polymer-based composite induced by multifunctional one-dimensional nanofibers oriented in-plane direction

As advanced dielectric materials for the applications in electronics and electrical power systems with the ever-increasing requirements, the polymer-based dielectric nano-composites are brilliantly emerging. However, there are long standing challenges of the unsatisfactory electric breakdown strength and the heat accumulation induced by dielectric loss of composite. In this study, we propose an artificial nano-composite with excellent comprehensive performance by controlling the orientation of one-dimensional (1D) 0.5Ba(Zr0.2Ti0.8)O3-0.5(Ba0.7Ca0.3)TiO3 nanofibers (BZCT NFs) and adjusting the interaction between BZCT NFs and poly(vinylidene fluoride) (PVDF) matrix via SiO2 buffer layer. Remarkably, PVDF nano-composite with only 3 vol% aligned BZCT NFs coated by SiO2 (BZCT@SiO2 NFs, 3 vol% Aligned BZCT@SiO2-PVDF) possesses an impressive energy storage performance, including the superior Weibull characteristic breakdown strength (Eb) of ~576 kV/mm and the ultrahigh discharged energy density (Ue) of ~18.9 J/cm3. Meanwhile, the temperature distribution in this typical composite is more homogeneous according to the test and simulation results. This demonstrated work not only opens a new door to preparing an excellent performance of polymer-based dielectric nano-composites, but also points out a route to the industrialization of energy storage dielectrics.

Effect of Polyether Sulfone Resin on Micromorphology, Thermal, Mechanical, and Dielectric Properties of Epoxy–Bismaleimide Composite Material

In this study, 4,4′-diaminodiphenylmethane bismaleimide (BMI) was used as the matrix and epoxy resin (EP) and polyether sulfone (PES) were used as the toughening agent. PES/EP–BMI two-phase composites were prepared; they could be applied in more fields. The SEM results and energy spectrum analysis show a strong interaction between PES and EP–BMI molecules, and the surface of the two phases is fuzzy. PES dispersed uniformly in the EP–BMI matrix as the dispersed phase. The interface among phases is blurred and shows a mutual penetrating phenomenon. Furthermore, the cross-section of cracks is rough, and the directions change. This is a typical ductile fracture morphology. The highest bending strength and impact strength of PES/EP–BMI composite material are 144.9 MPa and 19.7 kJ/m2, 41.2% and 90% increases copmared with those of EP–BMI matrix resin, respectively, when the content of PES is 4 wt%. Moreover, the decomposition temperature of the composite reaches 407°C, 9°C higher than that of EP–BMI. However, excess PES has a negative effect on the thermal decomposition temperature. The addition of PES increases the dielectric constant and dielectric loss of composites though they increase only slightly. The comprehensive properties of composites are at their best when the content of PES is 4 wt%. Overall, this study facilitates the applications of PES/EP–BMI composites in a broad range of fields.

In situ synthesis of polyaniline/Sm-doped TiO2 nanocomposites: evaluation of structural, morphological, conductivity studies and gas sensing applications

Polyaniline (PANI)/samarium doped titanium dioxide (Sm-TiO2) nanocomposites were prepared through in situ polymerization of aniline with different contents of Sm-TiO2 nanoparticles. The structure and morphology of the nanocomposites were characterized by FT-IR, UV, XRD, HRTEM, SEM, DSC and TGA. The electrical performances of the nanocomposites were investigated by AC and DC conductivity measurements. The effect of nanoparticles on PANI with the carbon monoxide, ammonia and hydrogen sulphide gas sensing properties were also studied. The results from FTIR and UV show the interaction of nanoparticles with PANI. The XRD study revealed the systematic arrangement of nanoparticles within the polymer matrix. HRTEM and SEM analysis showed the uniform structure of nanocomposites with spherically shaped dispersion of metal oxide nanoparticles. The result from DSC analysis indicated an increase in glass transition and melting temperature of nanocomposites than that of PANI. The higher thermal stability of the nanocomposite by the incorporation of nanoparticles was confirmed from TGA studies. The AC conductivity, dielectric constant and dielectric loss of composites were higher than pure PANI and the magnitude of these properties increased with the loading of nanoparticles. The DC conductivity indicates an increase in conductivity with increase in concentration of nanoparticles. The addition of metal oxide nanoparticles to PANI imparts excellent gas sensitivity to different gas at room temperature. Hence fabricated nanocomposites showed excellent thermal properties along with increased electrical conductivity and gas sensitivity, such type of nanocomposite can be used as a substitute for PANI in electrical or nanoelectronic devices.

Nanocomposite of polyrotaxane derivative and graphene with increased dielectric constant

Polyrotaxane, owing to the special topological interlocked structure, has attracted more and more attention from researchers. In this paper, a new polyrotaxane derivative has been synthesized based on the polyrotaxane end capped by 2, 4-dinitrofluorobenzene (DNFB). And through cross-linking the polyrotaxane derivative meanwhile adding graphene filler, high dielectric constant elastomeric nanocomposite is fabricated according to percolation theory. SEM images show that the addition of polyvinylpyrrolidone (PVP) improves the dispersibility of graphene in the cross-linked matrix. The percolation threshold of composite with PVP-modified graphene is 2.45 vol.% and for unmodified composite it is 2.20 vol.%. Besides, the dielectric constant of composite with PVP-modified graphene increases sharply to 289.8 with graphene content of 2.35 vol.% which is 25 times higher than that of matrix. However, the dielectric loss of composite is just 0.46. What is more, the thermal stability of composites shows an obvious enhancement compared to the polymer matrix. And the composite films still exhibit great flexibility at room temperature.

Ceramic-Polymer Composites with Low Dielectric Loss for Microwave Antennas and Wireless Sensors

The low dielectric loss ceramic-polymer composites were prepared by extrusion processing technique with high density polyethylene (HDPE) as matrix and high permittivity ceramic powder in BaO-Nd2O3-TiO2 (BNT) system as filter. The dielectric response in microwave frequency range was characterized, and the experimentally observed dielectric properties were compared with the theoretical models. The relative permittivity of the composites is increased from 3 to 10 with the increase in the volume fraction of BNT filter from 10 to 40 vol%. The dielectric losses of composites are less than 0.001 for all compositions. For 40 vol% ceramic loaded HDPE, the relative permittivity of 10 and loss tangent of 0.0007 at 7 GHz were obtained. The BNT-HDPE composites are promising materials for microwave dielectric antenna applications.

Microstructure and Properties of SCE‐Al2O3/PES‐MBAE Composite

SCE‐Al2O3 was the nano‐Al2O3 modified by supercritical ethanol and the surface of SCE‐Al2O3 was coated with active group. 4,4′‐diaminodiphenylmethane bismaleimide (MBMI) was used as matrix; 3,3′‐diallyl bisphenol A (BBA) and bisphenol‐A diallyl ether (BBE) were used as reactive diluent, polyethersulfone (PES) as toughening agent, and SCE‐Al2O3 as modifier; SCE‐Al2O3/PES‐MBAE nanocomposite was prepared through in situ sol‐gel method. The mechanism of composite toughened by PES was observed and analyzed. FTIR indicated that the reaction between MBMI and allyl compound occurred and SCE‐Al2O3 had doped into the polymer matrix. SEM showed that PES particle was inlaid in matrix and presented as a two‐phase structure in matrix. The heat resistance, dielectric properties, and mechanical properties of SCE‐Al2O3/PES‐MBAE nanocomposites were evaluated. The results showed that with the incorporation of PES, although the toughness of the material improved, the heat resistance and dielectric properties of material declined, meanwhile. The adulteration of SCE‐Al2O3 could remedy the harmful effect caused by PES, while the content of SCE‐Al2O3 was reasonable. The decomposition temperature, dielectric constant, and dielectric loss of composite were 441.23°C, 3.63 (100 Hz), and 1.52 × 10−3 (100 Hz); the bending strength and impact strength were 129.22 MPa and 13.19 kJ/mm2, respectively, when the content of SCE‐Al2O3 was 3 wt% and PES was 5 wt%.

Dielectric Constant of nano- CCTO / Epoxy Composite

Nanocrystalline multiphase CaCu3Ti4O12 (CCTO) was prepared using Ca(NO3)2.4H2O, Cu(NO3)2.3H2O, TiO2 and C2H2O4.2H2O. The X-Ray differection and SEM analysed of the prepared CCTO powder sintered at 900 o C and 950 o C. A homogeneous ceramics-polymer nanocomposites consisting of CCTO particles as fillers and epoxy polymer as matrix have been prepared using a casting process. The nanocomposites exhibit enhanced dielectric constant and dielectric loss. Dielectric properties of CCTO ceramics were characterized in a broad frequency range (100 Hz-1 MHz) and at a temperature ranged from 25 o C to 150 o C. As a result of increasing the content of CCTO, the dielectric constant and dielectric loss of composites are increased. The increase of dielectric loss at high frequencies is due to the relaxation process in the polymer matrix.

Effect of Functionalized MWCNTs with Surfactant and Coupling Agent on Properties of LDPE/POE Blends

The surfactant, sodium dodecylbenzenesulfonate (NaDDBS) and coupling agents, γ-aminopropyltriethoxy sliane (KH550) and isopropyl dioleic(dioctylphosphate) titanate (NDZ101) were used to treat multiwalled carbon nanotubes in this work. The effects of surface modification of multiwalled carbon nanotubes on crystallization behavior, mechanical properties, and electrical properties of low density polyethylene/polyolefin elastomer/multiwalled carbon nanotubes composites were studied. The results showed that NaDDBS, KH550, and NDZ101 had a favorable effect of improving the dispersion of multiwalled carbon nanotubes, but it cannot improve the interfacial interactionbetween multiwalled carbon nanotubes and the matrix. The improvement in dispersion favored the crystallization behavior and mechanical properties. Modified multiwalled carbon nanotubes had a better acceleration nucleation effect than raw multiwalled carbon nanotubes on low density polyethylene/polyolefin elastomer blends at low content (≤1 wt%). The tensile strength of low density polyethylene/polyolefin elastomer/multiwalled carbon nanotubes composites with modified multiwalled carbon nanotubes increased with lower multiwalled carbon nanotubes content (≤1 wt%), and KH550 and NDZ101 led low density polyethylene/polyolefin elastomer/multiwalled carbon nanotubes composites to possess a higher tensile strength than that of NaDDBS with 1 wt% content. NaDDBS, KH550, and NDZ101 had a minor influence on the dielectric properties of the composites and even caused a decrease in the dielectric loss of composites with 10 wt% multiwalled carbon nanotubes content.

Dielectric Properties of PMN/CB/CIIR Composites

The Magnesium Niobate-Lead Titanate (PMN) / conductive carbon black (CB)/ chlorobutyl rubber(CIIR) composites were prepared by blending-vulcanization method, and the dielectric properties were studied. The results showed that the dielectric constant and dielectric loss of composites increased nonlinearly when increasing the content of PMN or CB. From the curve of dielectric constant vs frequency, it is obtained that in the frequency range from 103 to 106 Hz, the dielectric constant of PMN/CB/CIIR composites decreased with the frequency increasing and the dielectric constants are more stable under high frequency.

BMI Based Composites With Low Dielectric Loss

O,O’-diallylbisphenol A (BA), allyl epoxy resins and epoxy acrylate resins are adopted to copolymerize with 4,4’-bismaleimidodiphenyl methane (BDM) resins and modify mechanical properties and processing charicteristics. The new modified BMI resin systems have more than two times improved impact strength without a great decrease in excellent dielectric properties or thermal and hot–wet resistance of neat BDM resin. Composites based on modified BMI resins and reinforced by glass fibre and quartz fibre possess excellent mechanical properties. The fracture surfaces of the composites are examined by scanning electron microscopy (SEM). It is indicted that modified BMI resin matrix composites put up typical toughness rupture and the adhesion efficiency in interface of composites is fine. When the test frequency scope is from 1 GHz to 20 GHz, the dielectric constant and dielectric loss of composites almost hold the line. After 100 h in boil water, mechanical and dielectric properties of composites are higher than 85% retention of their original values.

Novel 1–3 metal nanoparticle/polymer composites induced by hybrid external fields

We reported a novel 1–3 nanocomposite consisting of carbon-coated nickel (Ni@C) nanoparticles and epoxy resin matrix, in which nanoparticles were found one-dimensional-aligned by applying hybrid electric and magnetic fields during the curing of resin. The alignment was explained based on the dipole–dipole interaction between Ni@C nanoparticles under external fields. The dc resistivity, dielectric constant and dielectric loss of composites were tested as the function of the loading content and external fields. The results show the resistivity of aligned composites decreases by 3–4 orders of magnitude than that of random composites in the loading content range of 3–10 wt%, accompanied with an increase in dielectric constant and dielectric loss. Specially, it deserves to note that the synergistic effect of electric field and magnetic field was observed.