Dielectric Analyzer Research Articles

Static Dielectric Constants of Aqueous Glycol Solutions of Ethylene, Diethylene, Triethylene, Tetraethylene, Propylene, and Dipropylene

The static dielectric constants of aqueous glycol solutions for temperatures 35 to 55°C were measured using a dielectric analyzer. The systems studied are: aqueous ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), tetraethylene glycol (T4EG), propylene glycol (PG), and dipropylene glycol (DPG) solutions. The static dielectric constants of the corresponding pure glycols were also measured for the same temperature range. The measured static dielectric constants of pure glycols were found in a good agreement with the literature values. The measured static dielectric constants of aqueous glycol solutions were correlated by using a Redlich–Kister type equation for the excess static dielectric constants of the solution. The average absolute percentage deviation for the calculations of the static dielectric constants of aqueous glycol solutions is 0.8%.

Preparation, thermal properties, morphology, and microstructure of phosphorus-containing epoxy/SiO 2 and polyimide/SiO 2 nanocomposites

A phosphorus-containing tri-ethoxysilane ( dopo-icteos) reacting from the nucleophilic addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide ( dopo) and 3-(trieoxysilyl) isocyanate ( icteos) was synthesized. The structure of dopo-icteos was confirmed by 1H, 13C, 31P NMR and IR spectra. A triethylamine catalyzed mechanism for the dopo-icteos synthesis was proposed and verified by NMR spectra. The phosphorus-containing epoxy/SiO 2 and polyimide/SiO 2 nanocomposites were prepared from the in-situ curing of diglycidyl ether of bisphenol A (DGEBA)/4,4-diaminodiphenylmethane(DDM)/ dopo-icteos, and imidization of poly(amic acid) of pyromellitic dianhydride (PMDA)/4,4′-oxydianiline (ODA)/ dopo-icteos, respectively. The microstructure and morphology were investigated by 29Si NMR, scanning electron microscope (SEM), EDS (Si and P mapping) analysis and atomic force microscope (AFM). The thermal properties, flame retardancy and dielectric properties of the organic–inorganic hybrids were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), limiting oxygen index (LOI), thermal gravimetric analysis (TGA) and dielectric analyzer (DEA).

Dielectric and thermal properties of polymer network based on bismaleimide resin and cyanate ester containing dicyclopentadiene or dipentene. III

AbstractA series of bismaleimide‐triazine (BT) resins were prepared from commercial bismaleimide (DDMBMI) and 2,6‐dimethylphenol‐dicyclopentadiene dicyanate ester (DCPDCY) or 2,6‐dimethylphenol‐dipentene dicyanate ester (DPCY). The thermal properties of cured BT resins containing DCPD or DP were studied using a dielectric analyzer (DEA), dynamic mechanical analyzer (DMA), and thermal gravimetric analyzer (TGA). These data were compared with that of DDMBMI cured with bisphenol A dicyanate ester (BADCY). The cured DDMBMI/DCPDCY or DDMBMI/DPCY exhibits a lower dielectric constant, dissipation factor, and moisture absorption than those of DDMBMI/BADCY. The effects of blend composition on the glass transition temperatures and thermal stability are discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1942–1951, 2007

Structure and characterization for conterminously linked polymer of short‐chain epoxy resin with triallyl isocyanurate and bismaleimide

AbstractThe short‐chain epoxy resin (SCER) was prepared direct from epichlorohydrin/bisphenol A (ECH/BPA). The resulted SCER and 4,4′‐diaminodiphenyl sulfone (DDS) with various weight percent of triallyl isocyanurate/4,4′‐bismaleimidophenylmethane (TAIC/BMI) were subsequently thermally coreacted to the corresponding high performance materials for high frequency application. They were characterized using potentiometry, Fourier transform infrared (FTIR), differential scanning calorimetry (DSC), thermogravimetric analyses (TGA), dielectric analyzer, and scanning electron microscope (SEM). Dynamic mechanical analysis (DMA) of polymers showed only a Tg indicating a low entropy, amorphous state and formed a conterminously linked polymer. The morphology of polymers revealed no phase separation. The formation of polymer was in good agreement with the proposed molecular structure, and has enhanced good thermal, mechanical, and electric properties. Furthermore, with lower nitrogen content was achieved UL‐94 V‐0 rating. No fume and toxic gas emission were observed during burning test for this system. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 2470–2480, 2006

Synthesis and properties of bismaleimide resin containing dicyclopentadiene or dipentene. VI

AbstractNew aromatic bismaleimides (BMIs), bis(4‐maleimidophenoxy‐3,5‐dimethylphenyl)dicyclopentadiene (DCPDBMI) and bis(4‐maleimido‐phenoxy‐3,5‐dimethylphenyl)dipentene (DPBMI), containing a large dicyclopentadiene (DCPD) or dipentene (DP) and aryl ether linkage, were synthesized from diamine bis(4‐aminophenoxy‐3,5‐dimethylphenyl)dicyclopentadiene (DCPDA) or bis(4‐aminophenoxy‐3,5‐dimethylphenyl)dipentene(DPA) and maleic anhydride by the usual two‐step procedure that included ring‐opening addition to give bismaleamic acid, followed by cyclodehydration to bismaleimide. The monomers were characterized by Fourier transform infrared spectroscopy, proton NMR, elemental analyses, and mass spectra. Their thermal polymerization was investigated by DSC. The presence of a large cycloaliphatic moiety in the backbone of the bismaleimide increased the curing temperature and reduced the reactivity of the maleimide bond. Thermal and electrical properties of cured bismaleimide resins were studied using a dielectric analyzer, dynamic mechanical analyzer, and thermal gravimetric analyzer. These data were compared with that of commercial 4,4‐bismaleimidodiphenylmethane (DDMBMI). The cured DCPDBMI or DPBMI exhibits a lower dielectric constant, dissipation factor and moisture absorption than those of DDMBMI. Copyright © 2006 Society of Chemical Industry

Dielectric analyses of a series of poly(2-hydroxyethyl methacrylate- co-2,3-dihydroxypropyl methacylate) copolymers

The dielectric spectra of a series of copolymers of 2-hydroxyethyl methacrylate (HEMA) and 2,3-dihydroxypropyl methacrylate (DHPMA) were investigated. Recently, the full range dielectric spectrum of poly(2-hydroxyethyl methacrylate) was reported. This study looks at the effects on the dielectric behavior as a result of 2,3-dihydroxypropyl methacrylate addition. The dielectric permittivity, ε′, and the loss factor, ε″, were measured using a dielectric analyzer in the frequency range of 0.6 Hz to 100 kHz and between the temperature range of −150 and 275 °C. The electric modulus formalism was used to reveal the viscoelastic and conductivity relaxations present in the polymers. Several notable changes were observed as 2,3-dihydroxypropyl methacrylate concentration increased. It was observed through DSC and DEA that the glass transition temperature decreased as DHPMA content increased. The secondary dielectric relaxations were also affected as it was recorded that the activation energy for the γ transition increased and the β relaxation decreased with DHPMA content. Ionic conductivity data prove that DHPMA facilitates ionic mobility more efficiently than HEMA.

Characterization and properties of an organic–inorganic dielectric nanocomposite for embedded decoupling capacitor applications

Abstract Polymer/aluminum nanocomposites have a high dielectric constant and a low dielectric loss because of the combined characteristics of polymer–ceramic (due to the insulating ceramic shell of an aluminum particle) and polymer–metal (due to the metal core of an aluminum particle) systems. In this work, an aluminum particle surface treatment was performed with an epoxide-functionalized silane coupling agent in order to further improve the dielectric properties and processibility of polymer/aluminum composites. Fourier transformed infrared spectroscopy (FTIR) and thermogravimetric analyzer (TGA) were used to characterize the aluminum particles before/after coupling agent treatment. It was found that the silane coupling agent was successfully grafted on the aluminum particle surface. Rheology studies of polymer/aluminum composites showed that the coupling agent treatment could significantly reduce the viscosity of the aluminum composites, which indicates coupling agent treatment can improve the processibility of aluminum composites at high filler loading levels. Dielectric properties, including the frequency responses and temperature coefficient of capacitance of the aluminum composites were studied with a dielectric analyzer (DEA). The microstructures of aluminum composites were characterized with a field emission scanning electron microscope (SEM). It was found that a coupling agent treatment can improve the aluminum particle distribution and thereby enhancing the dielectric constant of aluminum composites.

Dielectric and thermal properties of dicyclopentadiene containing bismaleimide and cyanate ester. Part IV

A novel bismaleimide (BMI), bis(4-maleimidophenoxy-3,5-dimethylphenyl)dicyclopentadiene (DCPDBMI), containing a large dicyclopentadiene (DCPD) and aryl ether linkage, was synthesized from bis(4-aminophenoxy-3,5-dimethylphenyl)dicyclopentadiene and maleic anhydride by the usual two-step procedure that included ring-opening addition to give bismaleamic acid, followed by cyclodehydration to bismaleimide. The monomers were characterized by Fourier transform infrared spectroscopy (FT-IR), proton nuclear magnetic resonance (NMR), elemental analyses (EA), and mass spectra (MS). A series of bismaleimide-triazine (BT) resins were prepared from synthesized bismaleimide (DCPDBMI) and then cured with 2,6-dimethyl phenol-dicyclopentadiene dicyanate ester (DCPDCY) at various molar ratios. Thermal properties of cured BT resins (DCPDBMI/DCPDCY) were studied using dielectric analyzer (DEA), dynamic mechanical analyzer (DMA) and thermalgravimetric analyzer (TGA). These data were compared with that of commercial bismaleimide (DDMBMI) cured with bisphenol A dicyanate ester (BADCY). The cured DCPDBMI/DCPDCY exhibits lower dielectric constant, dissipation factor and moisture absorption than those of DDMBMI/BADCY. The effects of blend composition on the glass transition temperatures and thermal stability are discussed.

2,6‐Diamino‐4‐phenylphenol (DAPP) copolymerized polyimides: synthesis and characterization

AbstractNovel soluble copolyimides containing phenyl and hydroxyl pendant groups were synthesized from pyromellitic dianhydride (PMDA) and two diamines, 2,6‐diamino‐4‐phenylphenol (DAPP) and 4,4′‐oxydianiline (ODA), in various ratios via thermal imidization. The structures and physical properties of the copolyimides were characterized by FTIR, elemental analysis, DSC, dynamic mechanical analysis (DMA), TGA, a universal testing machine for stress–strain behaviour, and a dielectric analyzer to study the effect of DAPP on the physical properties of the modified polymers. Copolyimides containing more than 40 mol% DAPP were soluble in hot N‐methyl‐2‐pyrrolidone (NMP), dimethylacetamide (DMAc) and dimethylformamide (DMF), and possessed a high glass transition temperature (358 °C) and a high modulus (3.9 GPa). Introduction of the diamine DAPP could also reduce the dielectric constant. A segment of imide linkages could convert to benzoxazole linkages by decarboxylation at temperatures higher than 420 °C under vacuum. Although the heat‐treated polybenzoxazoles (PBOs) exhibited many good properties, they were found to be too rigid and brittle to be processable for microelectronic applications. Copyright © 2005 Society of Chemical Industry

Dielectric behavior of polyaniline synthesized by different techniques

Polyaniline doped with dodecylbenzenesulfonic acid (Pani.DBSA) was synthesized by different procedures: by a dedoping–redoping process, by one step inverted emulsion polymerization and by one step aqueous dispersion polymerization. The effect of these different techniques on the electric properties (dielectric constant, dielectric losses, and complex electric modulus) of the corresponding emeraldine base has been studied by thermal dielectric analyzer (DETA) in the temperature range −130 °C to 200 °C and in frequency range 0.03–10 5 Hz. It was found that the preparation technique has significant influence on the dielectric properties of Pani. The different synthetic routes give rise to polyaniline with different distribution of electric relaxation process, indicating different chain structure. Emeraldine base from Pani.DBSA prepared by one step aqueous dispersion polymerization exhibits one single relaxation peak with narrow distribution whereas that prepared by inverted emulsion polymerization exhibits two relaxation peaks, indicating two-phase structure as indicated by a bimodal distribution of relaxation process. Emeraldine base from Pani.DBSA prepared by dedoping–redoping process presents an intermediary behavior. Percentage crystallinity of Pani.DBSA samples has also been investigated using wide-angle X-ray diffraction analysis. Pani.DBSA prepared by aqueous dispersion exhibited higher crystallinity degree, which agrees with the higher conductivity.

In situ microscope and impedance study of polymer electrolytes

Simultaneous impedance measurements and optical observations of polymer electrolytes were conducted in a computer-controlled setup, which combined a dielectric analyzer, a polarizing microscope with a heating stage and a digital camera. The polymer film was placed between glasses with ITO conductive layers in a cell preserving argon atmosphere. The setup allowed automated recording of impedance spectra and microscope images consecutively at a set of stabilized temperatures between −20 and 100 °C. Measurements were repeated at a constant temperature when a drift of impedance was detected. The influence of melting and crystallization phenomena on electrical properties of high molecular weight PEO and PEO:LiTFSI system (50:1 molar ratio) was investigated. The evolution of impedance spectra was correlated with changes of polymer morphology during various heating and cooling runs. Impedance spectra were analyzed by fitting an equivalent circuit, which modeled: the ionic conductivity, the dielectric constant, the electric polarization due to inhomogeneity in the bulk of sample and the electrode polarization. The results indicate that the large decrease of ionic conductivity is related to the closing of amorphous conductivity pathways by the growing spherulites in the first stage of crystallization, and to the densification of the structure and interfacial phenomena in the second stage.

Crystallization and melting of PEO:LiTFSI polymer electrolytes investigated simultaneously by impedance spectroscopy and polarizing microscopy

Simultaneous impedance measurements and optical observations of polymer electrolytes were conducted in an automated experimental setup that combined an impedance dielectric analyzer, a polarizing microscope with a heating stage and a digital camera. The polymer film was placed between glasses with ITO conductive layers, forming a transparent cell mounted in a custom designed holder that preserved argon atmosphere. Films of high molecular weight poly(ethylene oxide) with dissolved lithium bis(trifluoromethanesulfone) imide(LiTFSI) of two compositions: 50:1 and 6:1 (EO:Li molar ratio) were investigated in transparent cells above room temperature and in cells with gold electrodes in temperature range between −60 and 90 °C. Various heating and cooling runs enabled observation of the crystallization and melting. The results indicate that the decrease of conductivity observed in impedance spectra during crystallization is related to the closing of amorphous conductivity pathways by growing spherulites. In the dilute system, composition 50:1 EO:Li, amorphous areas were still visible in the film after the growth of spherulites ceased. In the film of composition 6:1, corresponding to the polymer–salt complex, densification of the structure and interfacial phenomena caused a large drop of conductivity at the late stage of crystallization. In the dense structure of crystallized P(EO) 6:LiN(CF 3SO 2) 2 film no amorphous areas were visible. Differences in the structure have a reflection in the relative change of conductivity caused by crystallization, which decreased six times for the 50:1 composition and 500 times for the 6:1 composition.

A broad spectrum analysis of the dielectric properties of poly(2-hydroxyethyl methacrylate)

The dielectric permittivity, ε′, and the loss factor, ε″, of dry poly(2-hydroxyethyl methacrylate) were measured using a dielectric analyzer in the frequency range of 0.1Hz to 100kHz and between the temperature range of −150 to 275°C. The dielectric response of the sub-Tgγ transition of PHEMA has been widely studied before but little to no DEA data above 50°C is present in the literature. In this study the dielectric spectrum is presented up to and above the Tg. The electric modulus formalism is used to reveal the γ, β, α and conductivity relaxations. The apparent activation energies for the relaxations are presented.

Synthesis of novel phosphorus-containing cyanate esters and their curing reaction with epoxy resin

Novel phosphorus-containing cyanate esters with phosphorus contents between 1–4% (badcypx, x=1–4) were synthesized from the addition reaction of 9,10-dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (dopo) and bisphenol A dicyanate (badcy). The structures of synthesized cyanate ester resins were confirmed by NMR and IR spectra. The modified cyanate esters were either self-curing (badcy and badcypx series) or curing with epoxy (badcye and badcypxe series). Thermal properties of cured cyanate ester were evaluated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermal gravimetric analysis (TGA), dielectric analyzer (DEA) and UL-94 vertical test. It was found that Tg and Td (5%) decrease markedly with the phosphorus content for the self-curing system, while Tg and Td (5%) decrease slightly with the increase of cyanate equivalent weight for the cyanate–epoxy curing system. The flame retardancy increases with the phosphorus content and a UL-94 V-0 rating can be achieved for cured badcyp2-badcyp4 and badcyp3e-badcyp4e. These flame retardant thermosets exhibit low moisture absorption as well as low dielectric constants and dissipation factors. Experimental results indicate that introducing the flame retardant phosphorus element into cyanate ester will not sacrifice its low dielectric characteristic.

Effect of processing temperature on the properties of sol–gel-derived mesoporous silica films

Mesoporous organically modified silicon oxides were fabricated using multi-step sol–gel technique with tetraethyl orthosilicate (TEOS) and methyltriethoxysilane MTES) as precursors. The characterization of the dielectric films with Fourier transform infrared, thermogravimetric (TG) and differential thermal analysis (DTA) as well as dielectric analyzer showed the effect of annealing temperature on the development of porosity and dielectric properties of the films. The pore size was measured by small angle X-ray scattering (SAXS) and was found that the annealing temperature did not affect the pore size very much during the experimental temperature range. An ultra-low dielectric constant of about 2.1 was realized for about 57% porosity in the silica film. It was shown that the method employed is useful for preparing new kinds of films used as interlayer dielectrics.

Chemorheological studies on a dicyanate resin modified with polyethersulfone

AbstractThe chemorheology of a dicyanate resin modified with a polyethersulfone (PES) was investigated. The rheological and dielectrical property changes during curing of the dicyanate resin system catalyzed by an organic metal salt were monitored by a rheometer and dielectric analyzer, respectively, and used to investigate the curing behavior and chemorheology of the resin system. The curing rate of the dicyanate resin system decreased as the PES content was increased. A function that can describe the viscosity change of the dicyanate resin system during curing was determined by a nonlinear regression method using the rheometer data. The gelation time of the dicyanate resin system decreased with increasing isothermal curing temperature and with decreasing PES content. The curing behavior of the dicyanate resin system monitored by the dielectric analyzer coincided fairly well with that measured by the rheometer Copyright © 2004 Society of Chemical Industry

Influence of long-chain branching on linear viscoelastic flow properties and dielectric relaxation of polycarbonates

Abstract The dynamic viscoelastic property, creep and creep recovery behavior, and dielectric relaxation of long-chain branched Bisphenol A polycarbonates were measured in parallel plate rheometer and dielectric analyzer. The linear polycarbonate (PC-L) as reference and three branched polycarbonates (PC-Bs) have similar molecular weights and molecular weight distributions, while the PC-Bs have different branching degrees, below 0.7 branch points/chain and above twice of M c . The long-chain branched polycarbonates exhibit higher zero-shear viscosities, more significant shear shinning, higher flow activation energies, and much longer relaxation times. It was also found that long-chain branches increase the elasticity of melt characterized by the steady-state recoverable compliance and the storage modulus. The ‘dissident’ rheological behavior of long-chain branching exhibiting mainly in addition polymers such as polyolefin, is confirmed in condensation polymers. These behaviors resulted from additional molecular entanglements of long-chain branches can be understood qualitatively in terms of the tube model for topological constraints. The dielectric α-relaxation of linear polycarbonate and branched polycarbonates has been fitted with Vogel–Fulcher–Tammann–Hesse (VFTH) equation and the shape of relaxation time curves is also analyzed. The long-chain branched polycarbonates present longer relaxation times, but divergent α-relaxation temperatures, because the latter is dominated by the free volume.

Homogeneous Dispersion of the Surface Modified MWNTs in the PU Matrix and Electrical Conductivity of the MWNTs/PU Composites

AbstractDispersion characteristics of the surface modified MWNTs (Miltiwalled nanotubes) in the PU (polyurethane) matrix and electrical conductivity of the MWNTs/PU composites are investigated using SEM and DEA (Dielectric analyzer) with respect to the chemical treatment of MWNTs, the kind of surfactants and their content. Several chemical treatments of the MWNTs' surfaces were performed with the acids type, acidic concentration, treatment temperature, and oxidation time. All the surface of modified MWNTs are negatively charged and functionalized with carboxylic group; however, the external walls of some MWNTs were severely damaged so that they were frequently thinned and partially cracked. Compared to those of the composites without the addition of surfactant, the surfactant embedded into composites show much better dispersion of the MWNTs and higher electrical conductivity, these results are in good agreement with the two step adsorption model of cationic surfactants proposed by Y. Gao. Both the optimized MWNTs and cationic surfactant filled PU composites show very low percolation threshold, pc = 0.0089±0.007 vol. %, and relatively higher conductivity after percolation than other carbon nanotubes composite systems reported elsewhere.

Synthesis and characterization of novel poly(amide‐imide)s containing 1,3‐diamino mesitylene moieties

AbstractA series of poly(amide‐imide)s were prepared using a new monomer, 1,3‐bis(trimellitimido)‐2,4,6‐trimethyl benzene (BTB), with four different diamines: 1,4‐phenylene diamine (PDA), 2,4‐diamino mesitylene (DAM), 2,2′‐dimethyl‐4,4′‐diamino biphenyl (DMDB), and 2,2′‐bis(trifluoromethyl)‐4,4′‐diamino biphenyl (TFDB). They were prepared by the condensation method in N‐methyl‐2‐pyrrolidinone (NMP) solvent using triphenyl phosphate and pyridine as condensing agents. The synthesized poly(amide‐imide)s were characterized by Fourier transform infrared and 1H NMR techniques. Films were prepared and characterized using DSC, thermogravimetric analysis (TGA), a prism coupler, and a film dielectric property analyzer. DSC measurement showed that the glass‐transition temperatures of the polymers were in the range of 259–327 °C. TGA analysis showed 5% weight loss, in the range of 472–514 °C. The refractive index varied from 1.6004 to 1.6586 in the following increasing order: BTB‐TFBM < BTB‐DAM < BTB‐DMDB < BTB‐PDA. For the poly(amide‐imide) films, the birefringence varied in the range of 0.0319–0.0580, in the following increasing order: BTB‐DAM < BTB‐TFBM < BTB‐DMDB < BTB‐PDA. The capacitance method showed that the dielectric constant of poly(amide‐imide) varied with the diamine structure; no difference was found by the optical method. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 137–143, 2004

Sol-gel synthesis of Na + beta-Al 2O 3 powders

Powders of general formula Na 1+ x Al 11O 17+ x/2 with x=0, 0.2 and 0.57 have been obtained by hydrolysis and condensation of metal alkoxides. X-ray diffraction investigations showed the crystallization of β-alumina peaks at 1100 °C, confirmed by DTA/TG measurements. The same phase was revealed for pellets sintered in air at 1400 °C. Densities up to 97% of the theoretical value were reached. Electrical performances of pellets of x=0.2 and 0.57 compositions were investigated by Dielectric Analyzer (DEA) at various frequencies. The measured values confirmed the good conductivity and activation energy performances of the material.