Enhancement of mechanical strength associated with interfacial tension between barium titanate and acrylonitrile–butadiene rubber with different acrylonitrile contents by surface modification

Acrylonitrile–butadiene rubber (NBR) with different acrylonitrile (ACN) contents was filled with barium titanate (BT) to prepare the polymer dielectrics. The neat NBR, NBR/untreated BT, and NBR/bis‐(γ‐triethoxysilylpropyl)‐tetrasulfide (silane coupling agent KH845‐4) modified BT (MBT) composites were prepared. At low ACN content (ACN content 20 wt %), the tensile strength of the NBR/MBT composites increased by 173.6% from 2.69 to 7.36 MPa compared to the neat NBR. The pleasing results were not found in those composites with high ACN content. Both surface modifications of BT and NBR with low ACN content would result in lower interfacial tension between BT and NBR. A strong interfacial adhesion was observed between MBT and NBR with 20 wt % ACN content. The interfacial adhesion had great contribution to the mechanical strength of composites. Moreover, the dielectric properties of composites were also investigated in detail. The addition of BT enhanced the dielectric constant of composites markedly. This study can be applied in manufacturing electronic devices, which are subjected to oily environments for a long time. At the same time, the study can provide some help for researchers to select the polymer matrix and the appropriate surface modification agent of functional filler. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45936.     

Enhancement of electromechanical properties of natural rubber by adding barium titanate filler: An electro-mechanical study

Natural rubber is one of the most potential electro-active polymers for sensors, actuators, and energy harvesting applications. Enhancing the characteristic properties of polymers by reinforcing with fillers that possess multifunctional attributes have attracted considerable attention. In the present study, barium titanate reinforced natural rubber composite is prepared by using two-roll mill mixing. Afterwards, mechanical, electrical, and electromechanical properties of the composites are extensively analyzed by reinforcing different amounts of barium titanate into the matrix of natural rubber. The fabricated dielectric composite shows excellent properties such as high dielectric constant, low dielectric losses, high dielectric breakdown strength, and extreme stretchability. It is observed that as the filler loading reaches the value of 11 parts per hundred rubber (phr), maximum agglomeration of the particles occurs. Maximum stretchability and highest ratio of dielectric constant to elastic modulus are obtained at 8 phr of barium titanate fillers and at the loading, a maximum actuation strain of 11.24% is achieved. This study provides a simple, economical, and effective method for preparing enhanced mechanical, electrical, and electromechanical properties of natural rubber composites, facilitating the wide applications of dielectric materials as actuators and generators.     

Processing,Dynamic mechanical thermal analysis,and dielectric properties of barium titanate/cellulosic polymer nanocomposites

High dielectric constant BaTiO₃/ethyl cellulose (BT/EC) nanocomposites having BT loadings of up to 13 vol% were fabricated through a simple casting technique. The BT filler powder, synthesized through an ultrasonic‐assisted solid‐state route, was revealed by X‐ray powder diffractometry (XRD) and Raman spectroscopy to be dominantly tetragonal. Scanning electron microscopy (SEM) showed good dispersion of the BT nanoparticles in the EC polymer matrix at lower BT concentrations. However, at higher concentrations, the BT particles form a continuous phase or a “filler network” leading to weak BT/EC interactions. This finding is well supported by the results of the tensile strength and storage modulus. The dielectric properties of the BT/EC nanocomposites were investigated over wide ranges of frequency and temperature. The addition of BT significantly increased the permittivity (ε ′) and dielectric loss (ε ″) and improved the ionic conductivity of the EC. The electric modulus (M″ ) results were analyzed in terms of the Havriliak–Negami function through three distinct relaxation mechanisms (namely α, β*, and β relaxations) in the temperature range 30–150°C. The dc conductivity (σ _dc) results suggest that the BT/EC nanocomposites formed at low BT loading (up to 7.0 vol%) and a temperature of ≤60°C are good candidates for antistatic applications while those formed at higher concentrations and temperatures are recommended for use in electrostatic dissipation applications. POLYM. COMPOS., 38:893–907, 2017. © 2015 Society of Plastics Engineers     

Effect of dehydroxylation of hydrothermal barium titanate on dielectric properties in polystyrene composite

In today's world, technology for capacitors has grown significantly with its requirements in the direction of better dielectric properties. Developing an ideal composite material (polymer and ceramic) for satisfying the processing parameters is of great interest for capacitor industry. In this study, chemically treated barium titanate (BT) nanocrystals were prepared and used to make ceramic–polystyrene (PS) composites. A unique methodology was used in processing these materials. Effects of the chemically treated BT, filler loading, and frequency on the dielectric properties of these composites were examined, and compared with untreated BT–PS composites. Composite dielectric constant was proportional to the volume ratio of the BT filler and remained stable at different frequencies. The experimental data show that the dielectric constant of composites made with treated BT powders can attain values 2.5 times higher than that of untreated BT–PS composites. In addition, the composite shows consistency in dielectric constant values measured at different frequencies. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci, 2006     

Mechanochemical preparation of devulcanized ground fluoroelastomers for the enhancement of the thermal stability of nitrile–butadiene rubber vulcanizates

Mechanochemically devulcanized ground fluoroelastomer (FKM) was used as a low‐cost functional additive for the enhancement of the thermal stability of nitrile–butadiene rubber (NBR) vulcanizates. Without the use of any chemicals, the stress‐induced mechanochemical devulcanization of ground FKM was achieved through solid‐state mechanochemical milling at ambient temperature. The sol fraction of the ground FKM was increased from its original 1.4 to 19.8% after milling; this confirmed the realization of the mechanochemical devulcanization of FKM. Moreover, the oxygen‐containing polar groups on the surface of the mechanochemically milled FKM benefitted its interfacial adhesion with the polar NBR matrix. The curing characteristics and mechanical properties of the devulcanized, FKM‐filled NBR vulcanizates were investigated and compared with those of the untreated FKM‐filled NBR vulcanizates. The results show that the mechanical properties of the devulcanized FKM‐filled NBR vulcanizates were much better than those of the untreated FKM‐filled NBR vulcanizates. The presence of the reclaimed FKM significantly increased the onset degradation temperature of the NBR vulcanizates as a result of the improved polymer–filler interaction, uniform dispersion, and high thermal stability of the reclaimed FKM. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Evaluation of cure characteristic,physico-mechanical,and dielectric properties of calcium copper titanate filled acrylonitrile-butadiene rubber composites: Effect of calcium copper titanate loading

Calcium copper titanate (CCTO) has been synthesized by high temperature solid-state reaction from calcium carbonate, copper (II) oxide, and titanium dioxide as the starting materials. The formation and morphology of CCTO were confirmed by X-ray diffraction, Fourier-transformed infrared spectrophotometry, scanning electron microscopy (SEM), and particle size analysis. In order to develop flexible dielectric materials, acrylonitrile-butadiene rubber (NBR)-based composites were prepared with CCTO content varied from 0 to 120 phr (parts per hundred rubber). The cure characteristics of composites were assessed. High-dielectric constant CCTO particles were blended into NBR to make composites with improved dielectric constant. Results showed that the NBR/CCTO composites had a high dielectric constant (10–20) with low dielectric loss (<0.4) and low conductivity (<10⁻³ μS/cm) at frequencies up to 10⁶ Hz. However, the higher CCTO loadings had agglomeration in the NBR matrix, and thus tensile strength and elongation at break sharply deteriorated due to poor rubber-filler interactions. The results showed lower storage modulus E′ and a reduction in T_g with the incorporation of CCTO in NBR matrix. Moreover, improved thermal stability of the NBR/CCTO composites was achieved. SEM was used to observe the dispersion of CCTO particles in NBR matrix.     

Enhancement of dielectric constants of epoxy thermosets via a fine dispersion of barium titanate nanoparticles

In this study, we examined a facile approach for achieving a fine dispersion of barium titanate (BT) nanoparticles (NPs) in epoxy thermosets. First, the surfaces of BT NPs were modified with poly(ε‐caprolactone) (PCL) via a surface‐initiated ring‐opening polymerization approach. We found that the PCL‐grafted BT NPs were easily dispersed in epoxy thermosets. The fine dispersion of the PCL‐grafted BT NPs in the epoxy thermosets was evidenced by transmission electron microscopy and dynamic mechanical thermal analysis. We found that the organic–inorganic nanocomposites displayed significantly enhanced dielectric constants and low dielectric loss compared to the control epoxy. The nanocomposites containing 14.1 wt % BT NPs possessed dielectric constants as high as at a frequency of 10³ Hz. The dielectric loss was measured to be 0.002 at a frequency of 10³ Hz. The improved dielectric properties are accounted for the fine dispersion of the BT NPs in the epoxy thermosets. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43322.     

High‐k dielectric composites of poly(2‐cyanoethyl vinyl ether) and barium titanate for flexible electronics

High‐k dielectric composite material for electronic applications was obtained by mixing a polymer with high dielectric constant, poly(2‐cyanoethyl vinyl ether) (CEPVA), and highly crystalline barium titanate (BT). Barium titanate nanoparticles of a size in the range 40–90 nm were prepared by the solvothermal method. By optimizing the reaction conditions, the formation of carbonate impurities and the agglomeration of formed nanoparticles were significantly reduced compared to state‐of‐the‐art procedures. Dielectric spectroscopy was measured in the range of 0.01 Hz to 10 MHz and showed the dielectric constant to be ?′ ～ 35–40 with only 30 vol % content of BT in the composite. Extrapolating to 100% BT nanoparticle concentration and using the Lichtenecker model, the dielectric constant ?′ = 365 ± 27 at 10 kHz was obtained. The relaxation and electrical properties were investigated in depth, and a new relaxation phenomenon was revealed. CEPVA/BT composite is considered suitable for electronic applications, in which high ?′ together with a good mechanical flexibility are required, such as organic field effect transistors. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45236.     

Hydroxyapatite‐barium titanate piezocomposites with enhanced electrical properties

The present work aims to obtain Hydroxyapatite (HA) ‐ Barium Titanate (BT) piezocomposites with improved electrical properties by retaining OH^? ions and tuning BT grain size. Dense piezocomposites of HA‐BT were obtained, using single step Spark Plasma Sintering. The presence of OH^? ions in the sintered piezocomposites of HA‐BT was confirmed by thermal characterization and Fourier transform infrared transmittance. No decomposition/interaction between HA and BT phases were observed in the complete range of temperature studied. The dielectric and pyroelectric properties were studied as a function of temperature (100 K to 450 K) and frequency (100 Hz to 2 MHz). The influence of the ferroelectric grain size (300 and 500 nm) on the electrical properties of HA‐BT has been analyzed. The dielectric permittivity of HA‐BT ceramics can be enhanced with appropriate ferroelectric grain size and volume fraction of BT (<80%).     

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     

High dielectric constant polyaniline/sulfonated poly(aryl ether ketone) composite membranes with good thermal and mechanical properties

All‐organic polyaniline (PANI)/sulfonated poly(aryl ether ketone) (SPAEK) composite membranes consisting of a PANI (conducting) filler evenly distributed in an SPAEK (insulating) matrix were prepared with a solution‐blending technique. The dielectric properties, electrical conductivity, and thermal and mechanical performances of the all‐organic PANI/SPAEK composite membranes were investigated as a function of different PANI loading levels. The composite membrane containing 30 wt % PANI exhibited a high dielectric constant of about 600, a low dielectric loss tangent of about 0.6 (at 1 kHz), and good thermal properties (temperature for 5% weight loss > 250°C) and mechanical properties (tensile strength ≈ 35 MPa). © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1990–1995, 2013     

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     

Thermoplastic polyurethane and nitrile butadiene rubber blends with layered double hydroxide nanocomposites by solution blending

Polymer blending coupled with nanofillers has been widely accepted as one of the cheaper methods to develop high‐performance polymeric materials for various applications. In the present work, dodecyl sulfate intercalated Mg? Al‐based layered double hydroxide (DS‐LDH) was used as nanofiller in the synthesis of polyurethane blended with nitrile butadiene rubber (PU/NBR; 1:1 w/w) nanocomposites, which were subsequently characterized. X‐ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the partial dispersion of Mg? Al layers in PU/NBR blends at lower filler content followed by aggregation at higher filler loading. In comparison to the neat PU/NBR blend, the tensile strength (156%) and elongation at break (21%) show maximum improvement for 1 wt% filler loading. The storage and loss moduli, thermal stability and limiting oxygen index of the nanocomposites are higher compared to the neat PU/NBR blend. Glass transition temperature and swelling measurements increase up to 3 wt% DS‐LDH loading in PU/NBR compared to either neat PU/NBR or its other corresponding nanocomposites. XRD and TEM analyses indicate the partial distribution of DS‐LDH in PU/NBR blends suggesting the formation of partially exfoliated nanocomposites. The improvements in mechanical, thermal and flame retardancy properties are much greater compared to the neat blend confirming the formation of high‐performance polymer nanocomposites. Copyright © 2009 Society of Chemical Industry     

Reduced sedimentation of barium titanate nanoparticles in poly(vinylidene fluoride) films during solution casting by surface modification

Reduced sedimentation of barium titanate (BaTiO₃, BT) nanoparticles during solution casting to prepare the BT/poly(vinylidene fluoride) (PVDF) films is systematically investigated by surface modification of the BT nanoparticles. The surface of BT nanoparticles is hydroxylated by hydrogen peroxide (H₂O₂) or aminated by γ‐aminopropyl triethoxysilane (γ‐APS). It is found that the compatibility between the fillers and polymer matrix is remarkably improved by such surface treatments. As a result, the agglomeration and sedimentation of BT nanoparticles in the BT/PVDF composite films are significantly reduced, which is supported by morphology observation. Better dielectric properties such as higher dielectric constant, higher breakdown strength, and lower dielectric loss are also obtained for the composite films with surface‐modified fillers than those with raw fillers. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42662.     

Electrical and thermal properties of γ‐irradiated nitrile rubber/rice husk ash composites

The effects of both the rice husk ash (RHA) loading and fumed silica (FS) loading on the structure, thermal stability, and electrical properties of acrylonitrile–butadiene rubber (NBR) composites were studied. The filler loading were chosen to be 5 and 20 phr for RHA and 5 and 30 phr for silica. Also, the effect of the γ‐irradiation dose (25 kGy) on these parameters was investigated. The structure and thermal stability were studied with X‐ray diffraction and thermogravimetric analysis techniques. Furthermore, some electrical parameters, such as the direct‐current electrical conductivity (σ_dc), activation energy (E_a), dielectric constant (?′), and dielectric loss (?″), were determined. The incorporation of both RHA and FS resulted in improved thermal stability after γ irradiation at 25 kGy. The loading of FS on NBR was shown to decrease σ_dc, ?′, and ?″ and increase E_a. On the other hand, the loading of RHA showed the opposite trend. Finally, γ irradiation of NBR composites filled with both fillers decreased the values of σ_dc, ?′, and ?″ for all the samples, which followed the trend for the unirradiated composites. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Mechanical,dielectric, and thermal properties of fluorosilicone rubber composites filled with silica/multiwall carbon nanotube hybrid fillers

In this work, hybrid fillers consist of modified silica (SiO₂) and multiwalled carbon nanotube (MWCNT) were used to improve the mechanical, dielectric, and thermal properties of fluorosilicone (FSR) composites via a direct mechanical mixing method. With the increase of CNT loading in SiO₂/CNT hybrid loading ratio, the tensile properties, dielectric constant, electrical conductivity, and thermal properties all increase without a sharp sacrifice of flexibility. The dielectric constant of FSR-S15/C5 achieved 7,370 @1 kHz, which is about four orders of the FSR-S20, and the dielectric loss remains as low as 0.676 @1 kHz. Therefore, the linkage of SiO₂ and FSR chains not only enhances the interfacial interaction between the fillers and FSR matrix but also decreases the agglomeration of the fillers in matrix. What is more, modified SiO₂ and CNT were designed as the effective hybrid filler to improve the performance of the polymeric matrix through synergic effect.     

Fabrication of barium titanate nanoparticles‐polymethylmethacrylate composite films and their dielectric properties

A method for incorporating barium titanate (BT) nanoparticles into polymethylmethacrylate (PMMA) is proposed to prepare composite films with a high dielectric constant and high transparency. BT particles with particle sizes of 7.8–24.0 nm and crystal sizes of 8.60–17.7 nm were synthesized with a complex alkoxide method. Surface of the BT particles was modified with 3‐methacryloxypropyltrimethoxysilane to introduce double bonds that was grafted with PMMA. The PMMA‐grafted BT particles were suspended in PMMA/N‐methyl‐2‐pyrrodinone solution and spin‐coated onto glass substrates to prepare the PMMA/BT composite films. The surface modification gave composite films having smooth surfaces and high transparency. An increase in BT particle size and BT volume fraction in the film tended to increase the dielectric constant while keeping the dissipation factor around 5%. The dielectric constant of the film prepared for a particle size of 24.0 nm at 39 vol% attained a value of 19.8 that was around four times higher than that of the pure PMMA film. The dielectric constants of the BT particles estimated by the application of Lichtenecker's mixing model to the composite films were 75.3, 105.1, and 166.3 for particle sizes of 7.8, 11.0, and 24.0 nm, respectively. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Enhancing dielectric properties of barium titanate macrofibers

The motivation of this work was to improve the dielectric properties of BaTiO₃ (BT) macrofibers by mixing BT nanofibers and commercial BT powder. BT nanofibers were fabricated via electrospinning synthesis. The calcined electrospun nanofibers were chopped and mixed with BT powder and converted in to a thermoplastic feedstock for extrusion of ceramic macrofibers with a diameter of 500 μm. The electromechanical properties of the BaTiO₃ macrofibers were investigated by varying calcination temperature of the nanofibers. For both nano and macro fibers, microstructure and phase composition was investigated by SEM and XRD. It could be observed that an increase in calcination temperature of the nanofibers enhanced the final electromechanical properties of the sintered macrofibers. The relative permittivity increased almost twice, the remanent polarisation increased about 4 times and the strain almost increased 10 times with the addition of calcined nanofibers to macrofibers.     

Electrical and Mechanical Properties of Thermoplastic Polyurethane and Polytetrafluoroethylene Powder Composites

To determine the possibility of using polytetrafluoroethylene (PTFE) powder as reinforcing filler in the thermoplastic matrix, the thermoplastic polyurethane (TPU) as the matrix and PTFE powder as reinforcing filler were used to prepare a particulate reinforced composite, in order to determine testing data for electrical and mechanical properties of the composites according to the filler loading in respect to TPU polymer matrix. The TPU and PTFE powder composites were prepared by the milling TPU with 2.5, 5, 7.5, and 10 wt% of PTFE powder in a two roll mill and the milled material is compression moulded to make sheets. From the sheets, the test specimens were made and tested for electrical properties—dielectric strength, dielectric constant, surface, and volume resistivity; fire resistance—rate of burning; mechanical properties—tensile strength and elongation, impact strength, hardness; density and melt flow index. The incorporation of PTFE powder has significantly improved the electrical properties—dielectric strength, dielectric constant, surface and volume resistivity; and fire resistance—rate of burning of thermoplastic polyurethane. However, the tensile strength decreased from 24.91 to 14.71 MPa and tensile elongation increased from 620 to 772 percentage.     

Thermal behavior and dielectric property analysis of boron nitride‐filled bismaleimide‐triazine resin composites

Bismaleimide‐triazine (BT) resin/hexagonal boron nitride (h‐BN) composites are prepared, and the effects of h‐BN content on the thermal and dielectric properties are studied in the view of structure–property relationship. It is found that the introduction of the BN in the BT resin dramatically improve the thermal conductivity of BT resin. The thermal conductivity of the composites is up to 1.11 W/m.K, with an h‐BN concentration of 50 wt %, which is increased by six times compared with the pure BT resin. The BT resin/h‐BN composites also exhibit excellent thermal properties, with the glass transition temperatures above 200°C, and thermal decomposition temperatures over 390°C. Moreover, the composites possess good dielectric properties. Their dielectric constant and loss tangent (tan δ) are less than 4.5 and 0.015, respectively. The results indicate that the BT resin/h‐BN composites are promising as efficient heat‐releasing materials in the high‐density electronic packaging technology. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013