Some aspects of microstructural and dielectric properties of nanocrystalline CdS/poly(vinylidene fluoride) composite thin films

Free‐standing flexible composite films of nanocrystalline cadmium sulfide‐impregnated poly(vinylidene fluoride) (nano‐CdS/PVDF) were prepared using a sol–gel technique. The effect of CdS loading, in the PVDF host matrix, on the dielectric properties was studied. An increase in dielectric constant (more than 10 times) was observed in the films when poled under an electric field. The composite films were also characterized using microstructural, Fourier transform infrared spectroscopy and X‐ray photoelectron spectroscopy measurements. © 2015 Society of Chemical Industry     

Dielectric behavior characterization of a fibrous‐ZnO/PVDF nanocomposite

This study is focused on forming a fibrous‐zinc oxide/polyvinylidine fluoride (ZnO/PVDF) nanocomposite and characterizing its dielectric behavior. The nanocomposite is prepared in two steps. First, a network of nanoscale diameter ZnO fibers is produced by sintering electrospun PVA/Zinc Acetate fibers. Second, the ZnO fibrous nonwoven mat is sandwiched between two PVDF thermoplastic polymer films by hot‐press casting. Scanning electron microscope images of the nanocomposite show that hot‐press casting of the fibrous‐ZnO network breaks the network up into short fibers. The in‐plane distribution of the ZnO fillers (i.e., the short fibers) in the PVDF matrix appears to comply with that of the pristine ZnO fibers before hot‐pressing, indicating that the fillers remain well‐dispersed in the polymer matrix. To the authors' knowledge, the work reported herein is the first demonstration of the use of electrospinning to secure the dispersion and distribution of a network of inorganic fillers. Moreover, processing a fibrous‐ZnO/PVDF flexible composite as described in this report would facilitate material handling and enable dielectric property measurement, in contrast to that on a fibrous mat of pure ZnO. Because of the high surface area of the short ZnO fibers and their polycrystalline structure, interfacial polarization is pronounced in the nanocomposite film. The dielectric constant is enhanced significantly‐up to a factor of 10 at low frequencies compared to the dielectric constant of constituent materials (both bulk ZnO and PVDF), and up to a factor of two compared to a bulk‐ZnO/PVDF composite. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

COOHMWCNTs‐induced BiFeO3‐poly(vinylidene fluoride) (PVDF) composites with enhanced dielectric and ferroelectric properties

In this work, flexible three phase composite films were prepared with surface functionalized multi‐walled carbon nanotubes (f‐MWCNTs) and bismuth ferrite (BiFeO₃;BFO) particles embedded into the poly(vinylidene fluoride) (PVDF) matrix via solution casting technique. The properties and the microstructure of prepared composites were investigated using an impedance analyzer and field emission scanning electron microscope. The micro‐structural study showed that the f‐MWCNTs and BFO particles were dispersed homogeneously within the PVDF matrix, nicely seated on the floor of the f‐MWCNTs separately. The dielectric measurement result shows that the resultant composites with excellent dielectric constant (≈96) and relatively lower dielectric loss (<0.23 at 100 Hz). Furthermore, the percolation theory is explored to explain the dielectric properties of the resultant composites. It says that the percolation threshold of f_MWCNTs = 0.9 wt % and the enhancement of the dielectric constant of the composite was also discussed. In addition, the remnant polarization of the un‐poled PVDF‐BFO‐f‐MWCNTs composites (2P_r ～1.34 µC/cm² for 1.1 wt % of f‐MWCNTs) is also improved. These three phase composites provide a new insight to fabricate flexible and enhanced dielectric properties as a promising application in modern electrical and electronic devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46002.     

COOH?MWCNTs‐induced BiFeO3‐poly(vinylidene fluoride) (PVDF) composites with enhanced dielectric and ferroelectric properties

In this work, flexible three phase composite films were prepared with surface functionalized multi‐walled carbon nanotubes (f‐MWCNTs) and bismuth ferrite (BiFeO₃;BFO) particles embedded into the poly(vinylidene fluoride) (PVDF) matrix via solution casting technique. The properties and the microstructure of prepared composites were investigated using an impedance analyzer and field emission scanning electron microscope. The micro‐structural study showed that the f‐MWCNTs and BFO particles were dispersed homogeneously within the PVDF matrix, nicely seated on the floor of the f‐MWCNTs separately. The dielectric measurement result shows that the resultant composites with excellent dielectric constant (≈96) and relatively lower dielectric loss (<0.23 at 100 Hz). Furthermore, the percolation theory is explored to explain the dielectric properties of the resultant composites. It says that the percolation threshold of f_MWCNTs = 0.9 wt % and the enhancement of the dielectric constant of the composite was also discussed. In addition, the remnant polarization of the un‐poled PVDF‐BFO‐f‐MWCNTs composites (2P_r ～1.34 µC/cm² for 1.1 wt % of f‐MWCNTs) is also improved. These three phase composites provide a new insight to fabricate flexible and enhanced dielectric properties as a promising application in modern electrical and electronic devices. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46002.     

Novel polymer–ceramic nanocomposite based on high dielectric constant epoxy formula for embedded capacitor application

Embedded capacitor technology can increase silicon packing efficiency, improve electrical performance, and reduce assembly cost compared with traditional discrete capacitor technology. Developing a suitable material that satisfies electrical, reliability, and processing requirements is one of the major challenges of incorporating capacitors into a printed wiring board (PWB). Polymer–ceramic composites have been of great interest as embedded capacitor material because they combine the processability of polymers with the high dielectric constant of ceramics. A novel nanostructure polymer–ceramic composite with a very high dielectric constant (ε_r ～110, a new record for the highest reported ε_r value of a nanocomposite) was developed in this work. A high dielectric constant is obtained by increasing the dielectric constant of the epoxy matrix (ε_r >6) and using the combination of lead magnesium niobate–lead titanate (PMN–PT)/BaTiO₃ as the ceramic filler. This nanocomposite has a low curing temperature (<200°C); thus, it is multichip‐module laminate (MCM‐L) process‐compatible. An embedded capacitor prototype with a capacitance density of 50 nF/cm² was manufactured using this nanocomposite and spin‐coating technology. The effect of the composite microstructure on the effective dielectric constant was studied. This novel nanocomposite can be used for integral capacitors in PWBs. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1084–1090, 2002     

An experimental model for predicting the piezo and dielectric constant of PVDF-PZT nanocomposite fibers with 0–3 and 1–3 connectivity

Energy harvesting from mechanical energy around ambient by flexible nanogenerators is one of the most efficient ways to generate green and renewable energy. Lead zirconate titanate (PZT) particles were embedded into a polyvinylidene fluoride (PVDF) polymer matrix to prepare mixed 0–3 and 1–3 connectivity nanocomposite fibers by electrospinning method. Various theoretical models of Maxwell-Garnett, Rayleigh, and Tinga etc were presented at two different Classes to predict the dielectric constant of PVDF-PZT nanocomposite fibers and compared the predicted results with the experimental results. Also, the piezoelectric properties like the piezoelectric coefficient (d₃₃) and piezoelectric voltage coefficient (g₃₃) were predicted by the Furukawa model and the predicted values were compared with the experimental values. Finally, the experimental model was derived to predict the dielectric constant of binary composites with mixed 0–3 and 1–3 connectivity. Compared to well-known models, the proposed experimental model accurately predicted the dielectric constant of PVDF-PZT nanocomposite fibers. The highest and lowest difference between the theoretical and the experimental results were obtained 12.24% and 0.12% for PZT volume fractions 1.1 and 17, respectively. Also, due to the linear relationship between the dielectric constant and piezoelectric coefficients, this model was generalized to predict the piezoelectric coefficients.     

Synthesis and dielectric properties of polystyrene‐clay nanocomposite materials

Polystyrene‐clay nanocomposite (PsCN) materials were synthesized and their properties of crystallinity, thermal behavior, and dielectric characteristics were investigated. A polymerizable cationic surfactant, [2‐(dimethylamino)ethyl]triphenylphonium bromide, was used for the intercalation of montmorillonite (MMT). The organophilic MMT was prepared by Na⁺‐exchanged MMT and ammonium cations of a cationic surfactant in an aqueous medium. Organophilic styrene monomers were intercalated into the interlayer regions of organophilic clay hosts followed by a free‐radical polymerization. Exfoliation to 2 wt % MMT in the polystyrene (PS) matrix was achieved as revealed by X‐ray diffraction (XRD) and transmission electron microscopy (TEM). Thermal properties by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also studied. The dielectric properties of PsCNs in the form of film with clay loading from 1.0 to 5.0 wt % were measured under frequencies of 100 Hz–1 MHz at 25–70°C. A decreased dielectric constant and low dielectric loss were observed for PsCN materials. The dielectric response at low frequency that originated from dipole orientation was suppressed due to the intercalation of clay materials. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1368–1373, 2004     

High dielectric constant SU8 composite photoresist for embedded capacitors

A novel, photodefinable, high dielectric constant (high‐k) nanocomposite material was developed for embedded capacitor applications. It consists of SU8 as the polymer matrix and barium titanate (BT) nanoparticles as the filler. The UV absorption characteristics of BT nanoparticles were studied with a UV‐Vis spectrophotometer. The effects of BT nanoparticle size, filler loading, and UV irradiation dose on SU8 photopolymerization were systematically investigated. The dielectric properties of the photodefined SU8 nanocomposites were characterized. Embedded capacitors using the novel high dielectric constant SU8 composite photoresist were demonstrated on a flexible polyimide substrate by the UV lithography method. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1523–1528, 2007     

A large enhancement in dielectric properties of poly(vinylidene fluoride) based all-organic nanocomposite

A nanocomposite was fabricated using poly(vinylidene fluoride) (PVDF) as matrix and poly(p-chloromethyl styrene) (PCMS) grafted with high dielectric constant copper phthalocyanine oligomer (CuPc) (PCMS-g-CuPc) as filler. Transmission electron microscopic morphologies reveal that the PCMS-g-CuPc particle size of ca. 80 nm in average are dispersed in PVDF matrix, while in PCMS-g-CuPc particles the PCMS acts as “matrix” which contains dispersed CuPc balls with a average size of ca. 25 nm [1/20 of that of CuPc in simple blend of PVDF and CuPc (PVDF/CuPc)]. The nanocomposite with only 15 wt% CuPc can realize a dielectric constant of 325 at 100 Hz, about 7 times larger than that of PVDF/CuPc, and nearly 40-fold enhancement with respect to that of the pure PVDF. The significant enhancement of dielectric response can be attributed to the remarkably strengthened exchange coupling effect as well as the Maxwell-Wagner-Sillars polarization mechanism.     

Enhanced dielectric properties of three phase dielectric MWCNTs/BaTiO3/PVDF nanocomposites for energy storage using fused deposition modeling 3D printing

This research studied the effect of fused deposition modeling (FDM) 3D printing on three phase dielectric nanocomposites using poly(vinylidene) fluoride (PVDF), BaTiO₃ (BT), and multiwall carbon nanotubes (CNTs). PVDF polymer and BT ceramics are piezo-, pyro- and di-electric materials extensively used for sensor and energy storage/harvesting applications due to their unique characteristic of dipole polarization. To increase dielectric property, CNTs have been recently utilized for uniform dispersion of BT nanoparticles, ultrahigh polarization density, and local micro-capacitor among matrix. It was proved that 3D printing process provides homogeneous dispersion of nanoparticles, alleviating agglomeration of nanoparticles and reducing micro-crack/voids in matrix which can potentially enhance their dielectric property than traditional methods. In this research, these three-phase nanocomposites are fabricated through FDM 3D printing process and characterized for dielectric property. Increasing both BT and CNT nanoparticles improves dielectric properties, while CNTs have a percolation threshold near 1.7?wt%. The most desirable combination of dielectric constant and loss properties (118 and 0.11 at 1?kHz) is achieved with nanocomposites containing 1.7?wt%-CNT/45?wt%-BT/PVDF. These results provide not only a technique to 3D print dielectric nanocomposites with improved dielectric property but also large-scale electronic device manufacturing possibility with freedom of design, low cost, and faster process.     

Development of Multiferroism in PVDF with CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Nanoparticles

Thin films of some polymer-ceramic nanomultiferroic composites (in 0–3 connectivity) of compositions (1-x) PVDF-xCoFe₂O₄ (x?=?0.05, 0.1, 0.5) have been fabricated through a solution casting route. Based on X-ray diffraction pattern and data, basic crystal structure and unit cell parameters were obtained. The surface morphology of the materials was studied using a scanning electron microscopy (SEM) technique. Structural investigation confirms the presence of a polymeric electro-active β-phase of matrix (PVDF) and nano filler spinel phase of the incorporated nano-ceramics. The observed SEM micrographs confirm that the nanoparticles are well distributed in the PVDF matrix without any agglomeration with a lesser spherulitic microstructure. The flexible nano-composites fabricated with polymer (PVDF) and CoFe₂O₄ provide high permittivity (relative dielectric constant) and low loss tangent. An impedance spectroscopy (IS) technique was employed to study the effect of grain and grain boundary in the resistive properties of the composite materials in terms of electric circuit. The study of AC conductivity as a function of frequency follows Jonscher’s power law. The improved conductivity and dielectric, magnetic, and measured first-order magnetoelectric coefficients suggest some promising applications in the embedded capacitors as well as in multifunctional devices.     

High dielectric permittivity and low loss in PVDF filled by core-shell Zn@ZnO particles

In this study, metal-semiconductor Zn@ZnO core-shell particles were prepared by the heat treatment of raw Zn powder under air atmosphere, and the prepared Zn@ZnO particles were incorporated into poly(vinylidene fluoride) (PVDF) to obtain high dielectric permittivity polymer. The results indicate that the Zn@ZnO particles remarkably increased the dielectric constant of the PVDF composites compared with the raw Zn/PVDF due to the duplex interfacial polarizations induced by ZnO-Zn interface and ZnO-PVDF interface. Moreover, the dielectric permittivity of the Zn@ZnO/PVDF composites can be further optimized by adjusting the thickness of ZnO shell. The dielectric loss and conductivity were still remained at low acceptable level owing to the presence of ZnO shell between Zn core and PVDF matrix which serves as an interlayer between the Zn cores preventing them from contacting with each other. The developed Zn@ZnO/PVDF polymer composites with high dielectric constant and low loss are potential for embedded capacitor applications.     

Effect of surface functionalization on the properties (rheological,mechanical, and dielectric) and microtopography of PEN/CPEN‐f‐CNTs nanocomposites

Novel carboxylic poly(arylene ether nitrile)s (CPEN) functionalized carbon nanotubes (CPEN‐f‐CNTs) were successfully prepared by a simple and effective solvent–thermal route. The CPEN‐f‐CNTs were subsequently used as the novel filler for preparation of high performance poly(arylene ether nitrile)s (PEN) nanocomposites. The SEM characterization of the PEN nanocomposites revealed that the CPEN‐f‐CNTs present better dispersion and interfacial compatibility in the PEN matrix, which was confirmed by the linear rheological analysis (Cole–Cole plots) as well. Consequently, the improved thermal stability (increased initial and maximum decomposition temperature) and enhanced mechanical properties (tensile strength and modulus) were obtained from nanocomposites using CPEN‐f‐CNTs. More importantly, the PEN/CPEN‐f‐CNTs nanocomposites not only show a high dielectric constant but also have low dielectric loss. For example, a dielectric constant of 39.7 and a dielectric loss of 0.076 were observed in the PEN composite with 5 wt% CPEN‐f‐CNTs loading at 100 Hz. Therefore, the flexible PEN/CPEN‐f‐CNTs nanocomposites with outstanding mechanical, thermal and dielectric properties will find wide application in the high energy density capacitors. POLYM. COMPOS., 37:2622–2631, 2016. © 2015 Society of Plastics Engineers     

Core‐shell structured Al/PVDF nanocomposites with high dielectric permittivity but low loss and enhanced thermal conductivity

Surface modification of core‐shell structured Al (Al@Al₂O₃) nanoparticles was performed using γ‐(Aminopropyl)‐triethoxysilane (APS) and dopamine (DA), respectively, and the microstructures, dielectric properties and thermal conductivities of the Al/poly(vinylidene fluoride) (PVDF) nanocomposites were investigated. Both DA and APS enhance the interfacial bonding strength between the fillers and the matrix, leading to homogeneous dispersion of Al nanoparticles in PVDF matrix. Compared with raw Al nanoparticles, surface‐treated Al/PVDF exhibit much higher dielectric permittivity due to the enhanced interfacial interactions between the two components, whereas, the dielectric loss and electric conductivity of the nanocomposites still remain at rather low levels owing to the insulating alumina shell preventing effectively core Al from direct contact. The dynamic dielectric properties results reveal that dielectric constant and loss increase with temperature due to the gradually enhanced mobility of molecular chain segments of PVDF for the raw Al/PVDF and treated Al/PVDF nanocomposites. Additionally, the PVDF nanocomposites with Al treated with APS and DA show enhanced thermal conductivities compared with raw Al/PVDF under the same filler loading because of reduced thermal interfacial resistance promoting phonon transfer across the interfaces. POLYM. ENG. SCI., 59:103–111, 2019. © 2018 Society of Plastics Engineers     

Preparation and characterization of silica/polyimide nanocomposite films based on water‐soluble poly(amic acid) ammonium salt

In this article, a series of new silica/polyimide (SiO₂/PI) nanocomposite films with high dielectric constant (>4.0), low dielectric loss (<0.0325), high breakdown strength (288.8 kV mm⁻¹), and high volume resistivity (2.498 × 10¹⁴ Ω m) were prepared by the hydrolysis of tetraethyl orthosilicate in water‐soluble poly(amic acid) ammonium salt (PAAS). The chemical structure of nanocomposite films compared with the traditional pure PI was confirmed by Fourier transform infrared spectroscopy and X‐ray diffraction patterns. The results indicated that both the PAAS and the polyamide acid (PAA) material were effectively converted into the corresponding PI material through the thermal imidization and the amorphous SiO₂ was embedded in the nanocomposite films without structural changes. Thermal stability of the nanocomposite films was increased though mechanical property was generally decreased with increasing the mass fraction of SiO₂. All the nanocomposite films exhibited an almost single‐step thermal decomposition behavior and the average decomposition temperature was about 615°C. It was concluded that the effective dispersion of SiO₂ particles in PI matrix vigorously improved the comprehensive performance of the SiO₂/PI nanocomposite films and expanded their applications in the electronic and environment‐friendly industries. POLYM. COMPOS., 38:774–781, 2017. © 2015 Society of Plastics Engineers     

Study of alternating current impedance analysis and dielectric properties of carbon nanotube‐based polysulfone nanocomposites

Polysulfone (PSU)/multiwalled carbon nanotubes (MWCNTs) nanocomposites containing 0.5–3 wt% of MWCNTs were prepared by solution casting technique. To understand the dispersion behavior of MWCNTs inPSU matrix, high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) were used. Electrical properties of nanocomposites were investigated by analyzing alternating current (AC) impedance spectra. The real part of complex impedance was decreased with increasing carbon nanotubes loading in the PSU matrix, which may be due to increase in conductive networks in the nanocomposite. The complex impedance Nyquist plots for PSU/MWCNTs nanocomposites were characterized by the appearance of a single semicircular arc, whose radii of curvature decreases with increasing MWCNTs loading. The polarization mechanism and the AC conduction mechanism were studied by designing equivalent circuit from impedance data. The dielectric response of PSU/MWCNTs nanocomposite was investigated over a wide range of frequency from 10 Hz to 10⁻⁶ Hz. Dielectric constant of PSU/MWCNTs nanocomposite was enhanced significantly from 2 to 6 × 10¹⁰ at 10 Hz when the addition of MWCNTs was increased from 0 to 3 wt%. The enhancement of dielectric property might be due to the interfacial polarization between carbon nanotubes and polysulfone. POLYM. COMPOS., 2012. © 2011 Society of Plastics Engineers     

Metallophthalocyanine-enriched Langmuir-Schaefer multilayers of poly(vinylidene fluoride)-based nanocomposites

Engineering the surface morphology with optimized crystallinity is very crucial for practical applications such as energy storage, electromechanical devices, and self-cleaning. Organic nanocomposites permit one to tune the dielectric properties by controlling the crystallinity and surface morphology. Here, we report our investigation on metallophthalocyanines of nickel and copper as an organic additive to poly(vinylidene fluoride) (PVDF) to modify the structural, optical, wetting, and electrical properties of the nanocomposite multilayers deposited using Langmuir-Schaefer method. The incorporation of the metallophthalocyanines in the nanocomposite multilayers was confirmed from the signature Bragg peaks, and the fingerprint absorbance using grazing incidence X-ray diffraction and Fourier transform infrared spectroscopy, respectively. Aggregation behavior of the metallophthalocyanines in the polar matrix of PVDF was studied using ultraviolet–visible spectroscopy. Surface morphological studies using field emission scanning electron microscopy on the nanocomposite multilayers show the presence of both spherical crystallites and rod-like structures which depends upon the composition and nature of metal in metallophthalocyanine. The surface wettability of these multilayers was investigated using static and dynamic contact angle studies. A significant enhancement in the dielectric constant has been observed for both nanocomposites relative to the pristine multilayer of PVDF. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47818.     

Dielectric dispersion and AC conductivity of acrylonitrile butadiene rubber‐poly(vinyl chloride)/graphite composite

Dielectric properties and ac electrical conductivity of Acrylonitrile Butadiene Rubber‐poly(vinyl chloride)/Graphite Composite were studied at different frequencies (10²?10⁶ Hz) in the temperature range (298–423 K). The results show that the dielectric constant (ε′), dielectric loss (ε″), ac electrical conductivity (σ_ac) and, the electric modulus are strongly dependent on the frequency and temperature. The dielectric constant ε′ increases with temperature and decreases with frequency, whereas the dielectric loss ε″ displays a broad maximum peak whose position shifts with temperature to a higher frequency region. Cole–Cole diagrams have been used to investigate the frequency dependence of the complex impedance at different temperature and graphite loading. Interfacial or Maxwell‐Wagner‐Sillars relaxation process was revealed in the frequency range and temperature interval of the measurements, which was found to follow the Havriliak–Negami approach for the distribution of relaxation times. At constant temperature, the frequency dependence of ac conductivity was found to fit with the established equation σ_ac(ω) = Aω^s quite well. The values of S for the investigated samples lie between 0.88 and 0.11. The conduction mechanism of ac conduction was discussed by comparing the behavior of the frequency exponent S(T) with different theoretical models. It was found that the correlated barrier hopping (C.B.H.) is the dominant conduction mechanism. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

GO@TA-Fe/PVDF纳米复合材料制备与介电性能

为降低氧化石墨烯（GO）/聚偏氟乙烯（PVDF）体系的介电损耗,本文采用单宁酸-铁配合物（TA-Fe）修饰GO表面,将改性GO和PVDF复合后制得了GO@TA-Fe/PVDF纳米复合电介质材料,研究了GO@TA-Fe对PVDF复合材料的微观形貌及介电性能影响。研究结果表明,TA-Fe包覆层强化了GO与PVDF基体间界面相容性及界面作用力,促进了GO在基体中均匀分散;TA-Fe界面层的存在显著降低了GO/PVDF漏导电流及损耗,归因于绝缘界面层有效阻止了GO之间直接接触,抑制漏导电流;TA-Fe用量对体系介电性能有明显影响,随TA-Fe用量增大,体系的介电损耗和电导率显著降低。与GO/PVDF相比,质量分数2%的GO@TA-Fe/PVDF在100Hz下介电常数为1000,而介电损耗由19.8降低为0.08。本研究制备的高介电常数及低损耗的柔性GO@TA-Fe/PVDF纳米电介质材料在电子器件及电力设备领域具有潜在应用。     

Ultra‐high dielectric constant of poly(vinylidene fluoride) composites filled with hydroxyl modified graphite powders

We provide a one‐step hydrothermal reaction to modify graphite powders (GPs) and prepare hydroxyl modified GPs/poly(vinylidene fluoride) (PVDF) composites which have excellent dielectric properties using high conductivity, low cost GPs as raw material. Fourier transform infrared spectroscopy (FT‐IR) and X‐ray photoelectron spectroscopy (XPS) showed that hydroxyl groups had been introduced to the surface of GPs. Scanning electron microscopy (SEM) showed that the hydroxyl modified GPs had better dispersion in the polymer matrix than the GPs. An ultra‐high dielectric constant of more than 5.1 × 10³ (dielectric loss is about 3.0) was obtained for the hydroxyl modified GPs/PVDF near the percolation threshold at 1 kHz. The hydroxyl modified GPs/PVDF composites exhibited better dielectric properties than most carbon/polymer composites. POLYM. COMPOS., 37:327–333, 2016. © 2014 Society of Plastics Engineers