Electrorheological fluids based on polymer electrolytes

The phenomenon of electrorheological activity taking part in so called electrorheological fluids (ERFs) relies on strong and reversible changes of fluid viscosity upon application of electric field and finds interesting technical applications. ERFs typically comprise dispersions of polarisable solid particles in liquid matrices. The paper describes studies on complexes of polyacrylonitrile with various salts of alkaline elements. The materials in a powder form were dispersed in silicone oil as well as in active matrices containing a liquid crystalline polymer. It was found that these novel systems were substantially anhydrous and electrorheologically active. The observed ER effect was relatively high and accompanied by very low current consumption. The magnitude of the ER effect was correlated with bulk ionic conductivity of the studied materials. The optimal bulk conductivity giving the highest ER effect at reasonably low currents amounted to about 10⁻⁵ S/cm. Higher conductivities resulted in higher currents only and saturation of the yield stress values. It was also shown that dispersions of the polymer complexes in a solution of poly(n-hexyl isocyanatye) in xylene manifested enhanced ER activity.     

Electrical energy density and dielectric properties of poly(vinylidene fluoride-chlorotrifluoroethylene)/BaSrTiO3 nanocomposites

A series of poly(vinylidene fluoride-chlorotrifluoroethylene) (P(VDF-CTFE))/barium strontium titanate (BST) nanocomposites were fabricated by solution casting method. The addition of BST nanoparticles could enhance both the dielectric constant and the displacement of the resultant composite significantly. The surface activation of BST nonaparticles with KH550 was confirmed as an effective way to improve the breakdown strength of the composite. The high electric displacement (D > 15 μC/cm²), breakdown field (>200 MV/m) and low dielectric loss in P(VDF-CTFE)/BST nanocomposites suggest that the high electrical energy density may be desirable. That indicates the potential application of this class of copolymer/ceramics nanocomposites for high energy storage components.     

Synthesis,characterization, and partial hydrolysis of polyisoprene‐co‐poly(tert‐butyl methacrylate) and electrorheological properties of its suspensions

The synthesis, characterization, partial hydrolysis, and salt formation of polyisoprene‐co‐poly(tert‐butyl methacrylate) and the electrorheological properties of its suspensions were investigated. The copolymer was characterized by gel permeation chromatography, viscosity measurements, ¹H‐NMR, Fourier transform infrared spectroscopy, particle size measurements, and elemental analysis. The poly(tert‐butyl methacrylate) units of the copolymer were partially hydrolyzed by p‐toluene sulfonic acid monohydrate and then converted into a lithium salt. The conductivity of this copolymeric salt was measured to be 1.4 × 10^?9 S cm^?1. Suspensions of the copolymeric salt were prepared in four insulating oils (silicone oil, mineral oil, trioctyl trimellitate, and dioctyl phatalate) in a series of concentrations (5–33%, m/m). The gravitational stabilities of these suspensions were determined at 20 and 80°C. The flow times of the suspensions were measured under no electric field (electric field strength = 0) and under an applied electric field (electric field strength ≠ 0), and the electrorheological activity was observed. Furthermore, the effects of the solid particle concentration, the shear rate, the electric field strength, a high temperature, and the addition of promoters on the electrorheological activities of the suspensions were investigated, and the excess shear stresses were determined. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1822–1833, 2004     

Electrorheological properties of chitin suspensions

Electrorheological suspensions are suspensins of solid particles whose rheological behavior can be strongly modified by the application of an electric field, In this article, the electrorheological properties of suspensions containing chitin particles (and its derivative— carboxylmethyl chitosan particles) in silicone oil are reported for a range of suspension weight concentrations, applied field strengths, shear rates, etc. In these suspensions, glycerin was used as an activator. The adsorbed amount of glycerin, one of the electrorheological parameters, was also studied experimentally. The ER effect of the chitin suspension reaches the maximum at about 11% of weight concentration. The dependence of the experimentally determined dynamic yield stress on particle concentration and field strength is found to be similar to that reported for other systems. The dynamic yield stress is found to increase with the particle concentration and the applied electric field strength. © 1996 John Wiley & Sons, Inc.     

Electrorheological fluids based on nano-fibrous polyaniline

Using a modified oxidative polymerization, the nano-fibrous polyaniline with 200 nm diameter and several micrometer lengths was synthesized on a large scale and then was applied as a new electrorheological (ER) fluid. Compared to conventional granular polyaniline ER fluid, the nano-fibrous polyaniline ER fluid exhibited distinctly improved suspended stability. Under electric fields, the nano-fibrous PANI ER fluid also exhibited larger ER effect. Its shear stresses are about 1.2-1.5 times as high as those of the granular PANI ER fluid. At the same time, the shear stress of nano-fibrous PANI ER fluid could maintain a stable level and even an increase for the wide shear rate regions from 0.1 s⁻¹ to 1000 s⁻¹ under various electric fields. In addition, the dynamic experiment showed that the shear modulus of nano-fibrous polyaniline ER fluid under electric field was higher than that of the granular polyaniline fluid, which also confirmed the larger ER effect.     

Preparation of polyaniline coated poly(methyl methacrylate) microsphere by graft polymerization and its electrorheology

Monodisperse acrylic microspheres (diameter 9.2 μm) (An-PGMA) with aniline moieties on the surface were initially prepared by a seeded emulsion method, and then composite particles (PA-PGMA) possessing polyaniline (PANI) shell were prepared via an in situ polymerization of aniline using An-PGMA particles as a core material inducing grafting polymerization of aniline. The PANI layer was found to be formed on the An-PGMA surface from the microscopic image, ¹³C FT-NMR and TGA of the PA-PGMA particles. Suspension of the PA-PGMA particle dispersed in silicone oil showed typical electrorheological (ER) characteristics under external electric fields.     

Rheology and properties of melt-processed poly(ether ether ketone)/multi-wall carbon nanotube composites

Poly(ether ether ketone) (PEEK)/multi-wall carbon nanotube (MWNT) composites containing up to 17 wt% filler were prepared using a twin screw extruder. Transmission electron microscopy (TEM) images reveal that the MWNTs were homogeneously dispersed in the PEEK matrix. Linear viscoelastic measurements show that both complex viscosity and moduli increase with increasing MWNT concentration. The storage modulus, G^′ exhibits a dramatic seven order increase in magnitude around 1 wt%, leading to a solid-like low-frequency behaviour at higher loadings; the effect can be attributed to network formation at a rheological percolation threshold. Rheotens measurements show that the melt strength also increases significantly on addition of nanotubes, however, the drawability decreases. An analytical Wagner model was used to calculate the apparent elongational viscosity over a wide range of elongational rates, and to reveal significant increases on addition of MWNTs, with a similar threshold behaviour. The electrical response is also dominated by percolation effects, increasing by nearly 10 orders of magnitude from 10⁻¹¹ to 10⁻¹ S/cm, on the addition of only 2 wt% MWNTs. In contrast, the thermal conductivity and tensile elastic modulus of the composites increased linearly with nanotube content, rising by 130% and 50%, at 17 wt% MWNTs, respectively.     

A novel electric elastomer based on starch/transformer oil drop/silicone rubber hybrid

The electrorheological fluid composed of starch particles and silicone oil/transformer oil was dispersed into 107 silicone rubber, and then two types of electric elastomers were prepared in the absence and presence of a curing electric field, respectively. The storage modules were measured using dynamic mechanical analysis with the round disk compression clamp. The results indicate that the storage modulus sensitivity of electric elastomers composed of pure transformer oil is the highest, that of electric elastomers composed of pure silicone oil takes second place, and that of electric elastomers composed of mixture oil is the smallest. For the given starch concentration, the storage modulus sensitivity attains a maximum value of 3.88 when the mass ratio between the transformer oil and 107 silicone rubber is 1. For the given mass ratio of 1, the effects of starch concentration and the presence or absence of the curing electric field on the storage modulus of electric elastomers were studied. When the starch concentration is 5 wt %, the storage modulus of the elastomer without the electric field (denoted as A‐elastomer) is 20.1 kPa, whereas that of the elastomer with the electric field (denoted as B‐elastomer) is 101.8 kPa. The storage modulus sensitivity attains a maximum value of 4.07. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Thermal stability of gelatin gels: Effect of preparation conditions on the activation energy barrier to melting

10, 20, and 40 wt.% aqueous gelatin gels were prepared under isothermal (annealing at 15, 20, and 25 °C for 15 to 120 min) and nonisothermal (cooling at 1 °C min⁻¹) conditions. Isoconversional kinetic analysis of DSC data on gel melting (gel-sol transition) of all types of gels revealed significant variations in the activation energy throughout the process. Activation energy barrier to melting of isothermally prepared gels was in the range 160-190 kJ mol⁻¹ and found to increase with increasing the annealing temperature that was the major effect discovered. Activation energy barrier to melting of nonisothermally prepared gels was determined to be around 120-140 kJ mol⁻¹ and increase with increasing the concentration. Local reversibility of the gel melting was demonstrated by using temperature modulated DSC.     

Optical responses, permeability and diol-specific reactivity of thin polyacrylamide gels containing immobilized phenylboronic acid

Thin semitransparent gels were prepared by radical copolymerization of N-acryloyl-m-aminophenylboronic acid (NAAPBA) and acrylamide (AAm) taken in molar ratios from 8:92 to 16:84, respectively, in water. The gels were characterized by the content of immobilized NAAPBA and monomer conversion. Scanning electron microscopy revealed the micrometer size pores in the dried gels. The wet gels displayed a linear optical response to sugars with sensitivity decreasing in the series: d-fructose, d-galactose, d-glucose, d-mannose, N-acetyl-d-glucosamine in the sugar concentration range from 1 to 40-60 mM at pH 7.3. Cross-linking of the gels with N,N-methylene-bis-acrylamide decreased the strength of optical response. Specific binding capacity of a diol-containing dye Alizarin Red S in the gels at pH 7.0 coincided with the content of immobilized NAAPBA indicating the 1:1 stoichiometry of the reaction and, therefore, good accessibility of the boronic acid ligands for water-soluble diols. Permeability of the gels was studied with a non-interacting dye Ethyl Orange exhibiting the pore diffusion coefficient of 1.4 × 10⁻⁷ cm²/s. The rate of optical response of the gels to glucose was found to be determined by diffusion of sugar into the relatively thick gels (l = 0.35-1 mm) with effective diffusion coefficients of 2 × 10⁻⁷ cm²/s. In the thinner gels (l = 0.1 mm) the input of other kinetic processes, such as affinity binding or structural rearrangements of the gel, was noticeable.     

Swelling behavior of amphiphilic gels based on hydrophobically modified dimethylaminoethyl methacrylate

The amphiphilic gels based on hydrophobically modified dimethylaminoethyl methacrylate with different 1-bromoalkanes (1-C_nH_2n+1Br, n = 2, 4, 6, 8, 12) were synthesized by radiation-induced polymerization and crosslinking. The length of alkyl side chains had significant influence on the swelling behavior of the resulting gels. The swelling degree of the gels decreased with the increase of side chain length, and the gel hardly swelled when n = 12. The effect of temperature and ionic strength on the swelling behavior of the resulting gels revealed that (1) the gels with longer side chains (n ≥ 8) had upper critical solution temperature, while other gels were not thermo-sensitive. (2) Antipolyelectrolyte effect was observed when immersing the gels (n ≥ 8) in NaCl solutions in certain concentration range. The dramatic difference in swelling behavior was attributed to the different gel structures. The gels with short side chains (n ≤ 6) had cellular structure of normal polyelectrolyte gels. The gels (n ≥ 8) had an aggregation gel structure caused by the hydrophobic interaction among alkyl groups and the formation of ion-cluster between tetra-alkyl ammonium cation and Br⁻, which had been analyzed with the aid of SEM, Br⁻-selective electrode and fluorescence molecular probe.     

Novel hydrazone based polymers as hole transporting materials

The novel family of hole transporting polymers containing hydrazone moieties is reported. The polymers were prepared in polyaddition reaction of hydrazone-containing diepoxydes with 4,4′-thiobisbenzenethiol in the presence of catalyst triethylamine (TEA). Obtained polymers were found to constitute novel polymeric hole transporting materials (TM) characterized by differential scanning calorimetry and time of flight method. The highest hole drift mobility in the newly synthesized polymers exceed 10⁻⁴ cm² V⁻¹ s⁻¹ at an electric field of 10⁶ V cm⁻¹ was observed in the TM with triphenylamine moieties.     

Preparation and characterization of thermally stable epoxy-titanate coatings

Epoxy-polyamide coatings are used to protect metallic substrates in corrosive atmosphere. Thermal stability of the coating can be improved by the addition of inorganic cross-linking agent. Epoxy resin is incorporated with small percentage of silicone resin and cured with two types of hardeners such as polyamide and butyl titanate. The physical properties, heat resistance properties and electrochemical impedance behaviour of these coatings on steel in 0.5 M NaCl solution have been studied. The result implies that the heat resistant character of the titanate-cured coating is increased from 260 to 370 °C. The impedance study has shown that the coating resistance exerted by both the systems is in the range of 10⁵ Ω cm² after 6 days of immersion in 0.5 M NaCl. FTIR and Raman spectroscopy analysis confirm the presence of titanate linkage in the cured polymer coating. Thermal stability data indicate that the epoxy silicone resin cured with titanate hardener possesses higher thermal stability than that cured by polyamide hardener.     

Network structures and dynamics of dry and swollen poly(acrylate)s. Characterization of high- and low-frequency motions as revealed by suppressed or recovered intensities (SRI) analysis of C NMR

We recorded temperature-dependent high-resolution ¹³C NMR spectra of dry and swollen poly(acrylate)s [poly(2-methoxyethyl acrylate) (PMEA), poly(2-hydroxyethyl methacrylate) (PHEMA), and poly(tetrahydrofurfuryl acrylate) (PTHFA)] by dipolar decoupled-magic angle spinning (DD-MAS) and cross-polarization-magic angle spinning (CP-MAS) methods, to gain insight into their network structures and dynamics. Suppressed or recovered intensities (SRI) analysis of ¹³C CP-MAS and DD-MAS NMR was successfully utilized, to reveal portions of dry and swollen polymers which undergo fast and slow motions with fluctuation frequencies in the order of 10⁸ Hz and 10⁴-10⁵ Hz, respectively. Fast isotropic motions with frequency higher than 10⁸ Hz at ambient temperature were located to the portions in which ¹³C CP-MAS NMR signals of swollen PMEA were selectively suppressed. In contrast, low-frequency motion was identified to the portions in which ¹³C DD-MAS (and CP-MAS) signals are most suppressed at the characteristic suppression temperature(s) T_s. Network of PMEA gels (containing 7 wt% of water) turns out to be formed by partial association of backbones only, as manifested from their T_s gradient at lowered temperature, whereas networks of PHEMA (containing 40 wt% of water) and PTHFA (9 wt% of water) gels are tightly formed through mutual inter-chain associations of both backbones and side-chains, as viewed from the raised T_s values for both near at ambient temperature. It is also interesting to note that flexibility of gel network (PMEA > PTHFA > PHEMA) characterized by the suppression temperature T_s (PMEA < PTHFA < PHEMA) is well related with a characteristic parameter for biocompatibility such as the production of TAT (thrombin-antithrombin III complex) as a marker of activation of the coagulation system.     

Enhanced heavy oil recovery through interfacial instability: A study of chemical flooding for Brintnell heavy oil

This study is aimed at developing an alkaline/surfactant-enhanced oil recovery process for heavy oil reservoirs with oil viscosities ranging from 1000 to 10,000 mPa s, through the mechanism of interfacial instability. Instead of the oil viscosity being reduced, as in thermal and solvent/gas injection processes, oil is dispersed into and transported through the water phase to production wells.Extensive emulsification tests and oil/water interfacial tension measurements were conducted to screen alkali and surfactant for the oil and the brine samples collected from Brintnell reservoir. The heavy oil/water interfacial tension could be reduced to about 7 × 10⁻² dyn/cm with the addition of a mixture of Na₂CO₃ and NaOH in the formation brine without evident dynamic effect. The oil/water interfacial tension could be further reduced to 1 × 10⁻² dyn/cm when a very low surfactant concentration (0.005-0.03 wt%) was applied to the above alkaline solution. Emulsification tests showed that in situ self-dispersion of the heavy oil into the water phase occurred when a carefully designed chemical solution was applied.A series of 21 flood tests were conducted in sandpacks to evaluate the chemical formulas obtained from screening tests for the oil. Tertiary oil recoveries of about 22-23% IOIP (32-35% ROIP) were obtained for the tests using 0.6 wt% alkaline (weight ratio of Na₂CO₃ to NaOH = 2:1) and 0.045 wt% surfactant solution in the formation brine. The sandpack flood results obtained in this project showed that a synergistic enhancement among the chemicals did occur in the tertiary recovery process through the interfacial instability mechanism.     

Mechanical behavior of starch/silicone oil/silicone rubber hybrid electric elastomer

Two types of electric elastomers were prepared by dispersing a uniform mixture of starch particles and silicone oil into 107 silicone rubber in the absence and presence of a curing electric field, respectively. The elastic modules were tested with dynamic mechanical analysis with the round disk compression clamp. The results indicate that the storage modulus sensitivity attains a maximum value of 0.55 at a mass ratio of 1 between silicone oil and 107 silicone rubber with the given starch concentration. When the mass ratio is 1 and the starch concentration is 10 wt%, the storage modulus of the A-elastomer without the electric field is 37.1 kPa, while that of the B-elastomer with the electric field is 127.9 kPa. The storage modulus sensitivity attains a maximum value of 2.44.     

Mechanical and electrical properties of hydrous electrorheological elastomers based on gelatin/glycerin/water hybrid

Aimed at improving the stability of geometrical shape, mechanical performance, and particles dispersion of electrorheological (ER) hydrous elastomers, a new gelatin water‐based elastic gels containing starch particles were prepared under an applied dc electric field, and their ER effects were described with the compression modulus and the electric resistivity. The result demonstrates that the mechanical and electrical properties of the ER elastomers are dominated by an externally applied electric field as well as the weight fraction of particles. On comparing with the same chemical composition, elastomers cured without a field and with barium titanate/gelatin water‐based elastomer, some conclusions are suggested: the object elastomer has stronger responses to a field than the same chemical composition elastomer, especially with higher weight fractions of particles. The object elastomer has steady geometrical shape and mechanical performance because of the addition of glycerin into the matrix, and has a better dispersion of particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 104: 1738–1743, 2007     

Use of vegetable oil in supported liquid membrane for the transport of Rhodamine B

The transport of Rhodamine B (RB) from aqueous feed solution containing sodium hydroxide through a flat supported liquid membrane (SLM) sheet containing vegetable oil as a carrier to an aqueous strip phase was investigated. The transport rate of Rhodamine B was found to increase with sodium hydroxide concentration in the feed phase. The influence of pH on the feed (source) phase, the effects of sulphuric acid concentration in the strip (receiving) phase, stirring speed, initial dye (RB) concentration and temperature were studied. Transport kinetics and stability of the membrane were also studied. Polytetrafluoroethylene (PTFE) with 1.0 µm pore size used as the membrane was found to be more permeable than that with 0.5 µm pore size. The feed solution at pH 11 ± 0.1 has the highest permeability. The initial feed solution concentration of 1.06 × 10^− 4 mol/L was completely extracted and stripped into 0.3 mol/L sulphuric acid solution in 5 h. Raising of pH in the feed solution from 7 to 13 ± 0.1 leads to an increase in dye permeation from 9.81 × 10^− 5 to 6.18 × 10^− 4 cm/s. It was observed that dye flux across the membrane tends to increase with stirring speed.     

Mechanical properties and microstructure of HDPE/AL(OH)3/silicone oil composite

The effect of surface modification on the mechanical properties and microstructure of the composites of high‐density polyethylene (HDPE), silicone oil, and aluminum hydroxide [Al(OH)₃] was investigated. The dispersion of silicone oil in the HDPE composites was studied by scanning electric microscope (SEM) and differential scanning calorimetry (DSC). In the HDPE/Al(OH)₃/silicone oil composites, two types of dispersion structure of silicone oil were observed resulting from different surface modifications. In the composites surface modified with titanate NDZ‐130, calcium stearate, or oleic acid, silicone oil encapsulates around Al(OH)₃ particles, and both the notched impact strength and the elongation at break are very high. However, in the composites surface modified with silane KH‐550 or silane‐g‐HDPE, silicone oil and Al(OH)₃ particles separately disperse in HDPE, and both the notched impact strength and the elongation at break are very low. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 1896–1903, 2002     

Electrical conductivity of graphite/polystyrene composites made from potassium intercalated graphite

Composites between graphite and polystyrene have been synthesized starting from potassium intercalated graphite and styrene vapor. This in situ polymerization process can be used to make electrically conductive composites containing well-dispersed thin graphite sheets. The conductivities of the composites increase as the number of ordered carbon layers increases. With only 10% graphite in a polystyrene matrix, an electrical conductivity up to 1.3 × 10⁻¹ S/cm can be obtained. The key is synthesizing a material with at least four ordered graphite layers (a stage IV complex) separated by polystyrene. This composite shows an improvement in conductivity over a control composite made by radical polymerization of styrene containing the same amount of dispersed graphite which had a conductivity of 5.0 × 10⁻³ S/cm. Characterization of the complexes by powder X-ray diffraction, scanning electron microscopy and electrical conductivity is presented.