Electro‐rheological properties of anhydrous ER suspensions based on phosphoric ester cellulose particles

The electro‐rheological (ER) behaviour of suspensions in silicone oil of phosphoric ester cellulose particles (average particle size 17.77 µm) was investigated at room temperature with electric fields up to 2.5 kV mm⁻¹ with the aim of developing anhydrous ER suspensions applicable over a wide temperature range. Anhydrous ER suspensions dispersing cellulose particles which were treated by phosphoric ester reaction of 2 mol phosphoric acid and 4 mol urea were measured; not only were the electrical characteristics such as dielectric constant, current density and electrical conductivity studied but also the rheological properties on the electric fields and volume fraction of dispersing particles. Anhydrous ER suspensions dispersing phosphoric ester cellulose particles showed very low current density, conductivity and very high performance of ER effect (τ_A/ τ₀ ≈ 1030) on the 2.5 kV mm⁻¹ electric field, and the yield stress (τ_y) had a quadratic dependence on electric fields. © 2000 Society of Chemical Industry     

Scaling of Yield Stress of Polythiophene Suspensions under Electric Field

Summary: Electrorheological properties in steady shear of perchloric acid doped poly(3‐thiopheneacetic acid), PTAA, particles in silicone oil were investigated to determine the effects of field strength, particle concentration, doping degree (conductivity values), operating temperature and nonionic surfactant. The PTAA/silicone oil suspensions show the typical ER response of Bingham flow behavior upon the application of electric field. The yield stress increases with electric field strength, E, and particle volume fraction, ?, according to a scaling law of the form, τ_y ∝ E^α · ?^γ. The scaling exponent α approaches the value of 2, predicted by the polarization model, as the particle volume fraction decreases and when the doping level of the particles decreases. The scaling exponent γ tends to unity, as predicted by the polarization model, when the electric field strength is low. The yield stress under electric field initially increases with temperature up to 25 °C, and then levels off. At electric fields above of 1.5 kV/mm, the yield stress increases significantly by up to 50% on addition of small amounts of a nonionic surfactant.

Effect of switching the applied electric field on the viscosity of a 20 wt.‐% highly HClO₄ doped polythiophene suspensions during stress sweep test.     

Polythiophene/borax conducting composite II: Electrorheology and industrial applications

In this study, polythiophene (PT) and polythiophene/ borax conducting composite (PT/borax) were in‐situ synthesized using FeCl₃ as oxidizing agent containing 89.2% PT and 10.8% borax. The electrorheological (ER), creep‐recovery, and vibration damping characteristics of the PT/borax composite were investigated. A volume fraction series (φ = 5–25%) of the PT/borax/silicone oil dispersions were prepared and sedimentation stabilities were determined. An ER activity was observed from the samples, when subjected to external electric field strength thus, they were classified as smart materials. Some parameters affecting the ER properties of the dispersions such as volume fraction, shear rate, electric field strength, frequency and temperature were investigated. Creep tests were applied to the suspensions to investigate the viscoelastic behaviors and recoverable viscoelastic deformations observed. Finally, real time vibration damping experiment was carried out on a modified automobile shock absorber and a 68% vibration damping capacity determined for borax/SO suspension system under E = 0.3kV/mm condition. POLYM. COMPOS., 2011.© 2011 Society of Plastics Engineers     

Polyindene/organo‐montmorillonite conducting nanocomposites. II. electrorheological properties

In this study, polyindene (PIn) and three PIn/organo‐montmorillonite (O‐MMT) nanocomposites namely K1: [PIn(94.5%)/O‐MMT(5.5%)], K2: [PIn(92.8%)/O‐MMT(7.2%)], and K3: [PIn(87.9%)/O‐MMT(12.1%)] were used to investigate the electrorheological (ER), creep‐recovery, and vibration damping characteristics. A volume fraction series (φ = 5–25%) of suspensions were prepared from the samples in silicone oil (SO). First, zeta (ζ)‐potentials and antisedimentation stabilities; second, ER properties of these nanocomposite/SO suspension systems were determined under externally applied electric field strengths. Besides, the effects of dispersed phase volume fraction, shear rate, electric field strength, and temperature onto ER performance of these suspensions were investigated and non‐Newtonian rheological behaviors were observed. The vibration damping capabilities of the suspensions were investigated using various rheological parameters on the electrorheometer and on an automobile shock absorber and a 66% vibration damping capacity were determined under an applied electric field strength, which is an important property from industrial point of view. Furthermore, the materials were subjected to creep and creep‐recovery tests and reversible viscoelastic deformations were determined. From the experiments carried out, the nanocomposites were classified as smart materials. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of polycarbonate–poly(methyl methacrylate) graft copolymer as a modifier improving the surface hardness of polycarbonate

In this study, poly(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid) (PAMPS) was synthesized using potassium persulfate (K₂S₂O₈) as initiator. PAMPS (M _n = 36,000 g/mol) was partially converted to a lithium salt (PAMPS–Li), and particle size was determined to be 40 μm. Suspensions of PAMPS–Li at various concentrations were prepared in silicone oil, mineral oil, dioctylphthalate (DOP), and trioctyltrimellitate (TOTM) insulating oils. Colloidal stabilities of these suspensions were determined at 20 and 80°C. The PAMPS–Li suspensions were observed to provide an electrorheological (ER) response upon the application of an external dc electric field. ER properties of these suspensions were investigated at various shear rates (γ˙) and electric field strengths (E). Further, effects of polar promoters and high temperature on ER activity were determined, and excess shear stresses (Δτ) were calculated. A shear‐thinning non‐Newtonian viscoelastic behavior was observed for the PAMPS–Li suspensions. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1106–1112, 2002     

Investigation of electrorheological properties and creep behavior of poly(oxymethylene)/polythiophene composites

In this study, electrorheological (ER) properties of polythiophene (PT) and poly(oxymethylene)/polythiophene (POM/PT), conducting composites having different compositions were investigated. The particle sizes of the composites were measured by dynamic light scattering method. Conductivities and dielectric properties of these composites were determined. Suspensions of PT and POM/PT composites were prepared in silicone oil (SO) at several concentrations (c = 5–25%, m/m) and their sedimentation stabilities were determined. The flow times of these suspensions at various dc electric field strengths were measured. The effects of dispersed particle concentration, particle size, shear rate, electric field strength, frequency, and temperature onto ER activities of these suspensions were investigated. Further, creep tests were applied to the composite suspensions and reversible viscoelastic deformations observed. POLYM. COMPOS., 2009. © 2009 Society of Plastics Engineers     

Viscoelastic characterization of semiconducting dodecylbenzenesulfonic acid doped polyaniline electrorheological suspensions

Dodecylbenzenesulfonic acid (DBSA)‐doped polyaniline particles were synthesized via emulsion polymerization, and electrorheological (ER) fluids were prepared by dispersing the synthesized polyaniline particles in silicone oil. The viscoelastic properties of DBSA‐doped polyaniline/silicone oil ER systems were examined using a vertical oscillation rheometer (VOR), which is designed for the rheological measurement of ER fluids, with a high voltage generator. Viscoelastic data obtained from the VOR were compared with those obtained from a commercial Physica rotational rheometer. The data from VOR were quite reliable in a broad range of both strain and frequency. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 108–114, 2001     

Conductivity and polarization of carbonaceous nanotubes derived from polyaniline nanotubes and their electrorheology when dispersed in silicone oil

Nitrogen-enriched carbonaceous nanotubes (N-CTs) were prepared by the heat treatment of conducting polyaniline (PANI) nanotubes and then were used as new carbonaceous electrorheological (ER) fluids. Characterization showed that the nanotubular morphology of the original PANI was preserved after heat treatment, whereas the chemical structure and conductivity were changed significantly depending on the heat treatment temperatures. Under electric fields, the rheological properties of the N-CT suspensions prepared by the ultrasonic dispersion of the N-CTs in silicone oil were measured. This showed that the N-CT suspensions possessed versatile ER performance including high ER efficiency, good dispersion stability, and temperature stability. Especially, compared to the corresponding heat treated granular PANI suspensions, the N-CT suspensions showed better dispersion stability and higher ER effect. Furthermore, the ER effect of N-CT suspensions could be adjusted by varying heat treatment temperatures and the N-CTs obtained at around 600 °C exhibited the maximum ER effect. This could be explained by the polarization response, which originated from the regular change of conductivity of N-CTs as a function of heat treatment temperatures.     

Synthesis,characterization and electrorheological properties of poly(o‐toluidine)/Zn conducting composites

In this study, the synthesis, characterization, and electrorheological (ER) properties of poly(o‐toluidine)/Zn, (POT/Zn), composites were investigated. Syntheses of the composites were carried out by a chemical method using ammonium persulfate, (NH₄)₂S₂O₈, (APS), as a free radical initiator. The composites were characterized by Fourier transform infrared (FTIR) spectroscopy, electrical conductivity, magnetic susceptibility, particle size measurements, and scanning electron microscopy (SEM). A series of Zn‐containing composites were prepared (0.8–7.6% by mass), and their conductivities were measured to be within the range of 1.7 × 10^?3–5.0 × 10^?2 Scm^?1. Magnetic properties of POT/Zn composites were analyzed by Gouy scale measurements; it was found that their conducting mechanisms are bipolaron. A series of particle size (13, 17, 18, 26, 83 μm) were prepared by ground milling the crude POT/Zn composites. Colloidal suspensions of POT/Zn composites were prepared in silicone oil (SO), at a series of concentrations (10–30%, m/m), and sedimentation stabilities were measured at 25°C. ER measurements showed that the POT/Zn/SO suspension system was ER active. Thus, the effects of solid particle concentration, shear rate, electric field strength, addition of polar promoters, and temperature (25–125°C) onto ER activities of suspensions were investigated. The ER activity of suspensions was increased with increasing particle concentration and electric field strength and decreasing shear rate and showing a non‐Newtonian flow behavior. τ = 1.1 kPa shear stress was reached for POT/Zn (4.1 wt %, Zn) composite under E = 2.0 kV, c = 15 (%, m/m), , and T = 25°C conditions. It was found that the ER activity was slightly decreased with increasing temperature. Further, the addition of polar promoters had no promoting effect on the ER activity of the suspensions and POT/Zn/SO system was classified as dry ER materials. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1058–1065, 2007     

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.     

Poly(Li‐2‐hydroxyethyl methacrylate)‐co‐poly(4‐vinyl pyridine): Molar mass effects on strong electrorheological response

Electrorheological (ER) fluids display remarkable rheological behavior, being able to convert rapidly and repeatedly from a fluid to a solid‐like when an external electric field (E) is applied or removed. In this study, electrical and ER properties of poly(Li‐2‐hydroxyethyl methacrylate)‐co‐poly(4‐vinyl pyridine), poly(Li‐HEMA)‐co‐poly(4‐VP), copolymeric salts (ionomers) were investigated. For this purpose six ionomers were synthesized with different molar masses. They were then ground‐milled for a few hours to obtain micron size ionomers. The particle sizes of the ionomers were determined by dynamic light scattering. Suspensions of ionomers were prepared in silicone oil (SO), at a series of concentrations (c = 5–30%, m/m). The gravitational stability of suspensions against sedimentation was determined at constant temperature (T = 25°C). Flow times of the suspensions were measured under no electric field (E = 0 kV/mm), and under an external applied electric field (E ≠ 0 kV/mm) strengths and a strong ER activities were observed for all the poly(Li‐HEMA)‐co‐poly(4‐VP)/SO suspensions. Further, the effects of suspension concentration, mole ratios of poly(HEMA) and poly(4‐VP), and the overall molar mass of the copolymers, shear rate, electric field strength, frequency, promoter, and temperature onto ER activities of ionomer suspensions were investigated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1065–1074, 2006     

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     

Emulsion polymerized polyaniline synthesized with dodecylbenzene-sulfonic acid and its electrorheological characteristics: Temperature effect

Dodecylbenzene-sulfonic acid (DBSA)-doped polyaniline (PANI) was prepared by emulsion polymerization, where DBSA was used as both an emulsifier and a dopant. The chemical structure and morphology of the DBSA were examined via FT-IR and SEM, respectively. Electrorheological (ER) properties of DBSA-doped PANI particles dispersed in silicone oil were studied under different operating temperatures and an applied electric field. Shear stress data as a function of shear rate fitted quite well with the Cho-Choi-Jhon (CCJ) shear stress model. Both deduced static and dynamic yield stresses were found to be collapsed into a universal scaling function. Furthermore, the Cole-Cole plot and the dielectric spectra gave relaxation times of the ER systems for different operating temperatures of dielectric measurements, confirming the correlation of dielectric properties with ER performance.     

Electrorheological properties of poly(aniline-co-o-ethoxyaniline) suspensions

Suspensions of copolyaniline containing ethoxy group, namely poly(aniline-co-o-ethoxyaniline), in silicone oil have been investigated as one of many potential candidates for dry-base electrorheological (ER) fluid systems. The copolyanilines were synthesized by a chemical oxidation of aniline and o-ethoxyaniline with various molar ratios in an acidic media, and the characteristics of these polymers were examined by using several techniques. By using FT-IR, SEM, and a particle size analyzer, we studied chemical structure, particle size, and the particle size distribution of the copolymer, respectively. A Physica rheometer equipped with a high voltage generator was also adopted to measure the rheological properties of ER fluids using the copolyaniline. Controlled shear stress mode was used for the shear rate sweep measurement, and the copolyaniline synthesized in this study was found to give a typical ER behavior, that is, shear stresses increase with increasing electric fields and volume fractions.     

Fabrication of semiconducting graphene oxide/polyaniline composite particles and their electrorheological response under an applied electric field

Semiconducting graphene oxide/polyaniline (GO/PANI) composite particles for potential electrorheological (ER) fluid applications were synthesized by the in situ dispersion polymerization of aniline in the presence of GO particles, which were prepared using a modified Hummers method. The electroresponsive ER characteristics of the composite when dispersed in silicone oil exhibited a phase transition from a liquid-like to solid-like state under an applied electric field. The morphology and composition of the composite particles were characterized by scanning and transmission electron microscopy and Raman spectroscopy. Its fibrillation phenomenon was observed by optical microscopy during the application of an external electric field. The bulk rheological characteristics of both the flow curve and yield stress were examined using a rotational rheometer equipped with a high voltage generator. The GO/PANI composite showed typical ER behavior, which demonstrated its potential applications as an ER smart material.     

Investigation of electrorheological properties of kaolin suspensions under DC fields

In this study, the electrorheological (ER) behavior of suspensions prepared from d₅₀ = 7 μm kaolin particulate, dispersed in insulating silicone oil (SO) medium, was investigated. ER activity of all the suspensions was observed to increase with increasing electric field strength (E), concentration (c), and decreasing shear rate ( ). Shear stress ( ) of kaolin suspensions increased linearly with increasing concentrations of the particles and with the applied electric field strength. The viscosity (η) of all suspensions was decreased sharply with increasing shear rate and showing a typical shear thinning non‐Newtonian viscoelastic behavior. It was observed that kaolin/silicone oil system studied in the present work was sensitive to high temperature. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3798–3802, 2007     

Enhanced dielectric and electrorheological properties of needle‐like TiO2/polyrhodanine core/shell hybrid nanostructure

In this study, antisedimentation, dielectric, electrorheological (ER) and creep–recovery properties of needle‐like TiO₂/polyrhodanine (PRh) nanocomposite were investigated. Antisedimentation ratio of needle‐like TiO₂/PRh was determined to be 45% after 30 days in silicone oil (SO). Polarizability and relaxation time of needle‐like TiO₂/PRh/SO system were determined to be 0.18 and 2.9 × 10^?5 s, respectively by the dielectric spectroscopy which was further used to evaluate the ER performance of the dispersion, and the data obtained were in good agreement with the overall ER results. ER properties of needle‐like TiO₂/PRh/SO system were determined by taking the effects of shear rate, shear stress, electric field strength, and temperature into account using a torque electrorheometer. Non‐Newtonian shear thinning behaviors were observed for the samples. Vibration damping capabilities of the dispersions were investigated by measuring their elastic and viscous moduli as functions of frequency, time, and electric field strengths. Enhanced and reversible viscoelastic deformations were recorded for needle‐like TiO₂/SO system from creep–recovery tests with 88% recovery under E = 3.5 kV mm^?1 condition; thus, the system was classified as a smart one and suitable for potential vibration damping applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43240.     

Synthesis,electrorheology, and creep behaviors of in situ intercalated polyindole/organo‐montmorillonite conducting nanocomposite

In this study, first polyindole (PIN) was synthesized using FeCl₃ as an oxidizing agent. Then, an organo‐montmorillonite (O‐MMT) was prepared from virgin montmorillonite (MMT) by cetyltrimethylammonium bromide (CTAB) quaternary ammonium salt. Further, PIN/O‐MMT conducting nanocomposite was prepared with 18% O‐MMT content. The samples of PIN, MMT, O‐MMT, and PIN/O‐MMT nanocomposite were characterized by FTIR spectroscopy, thermogravimetric analysis (TGA), X‐ray diffraction (XRD), elemental analysis, conductivity, magnetic susceptibility, density, particle size measurements, and scanning electron microscopy (SEM) method. Characterization results showed a successfully prepared PIN/O‐MMT nanocomposite having both intercalated and exfoliated structures. A series of concentrations (5–25%, m/m) were prepared from those above‐mentioned materials in silicone oil (SO) and their sedimentation stabilities were determined. The suspensions were subjected to an external electric field strength and electrorheological (ER) activity was observed. The effects of dispersed particle concentration, shear rate, external electric field strength, frequency, and temperature onto ER activities of these suspensions were investigated. Creep tests were applied to all the four suspensions and recoverable viscoelastic deformations observed. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

Synthesis, electrorheology and creep behavior of polyindole/polyethylene composites

In this study, polyindole (PIN) and polyindole/polyethylene (PIN/PE) conducting composites, having various amounts of PIN, were synthesized by chemical polymerization using FeCl₃ as an oxidizing agent and taking the ratio of salt:monomer as 3:1. The samples of PIN and PIN/PE composites were characterized by FTIR, UV–vis, TGA, SEM, Gouy scale magnetic susceptibility, conductivity (1.2 × 10⁻³ S cm⁻¹ > σ > 1.96 × 10⁻⁶ S cm⁻¹, at T = 25 °C) and density measurements. FTIR analysis suggested a 2,3-propagation mechanism for PIN formation. The ground milled samples were subjected to particle size analysis by dynamic light scattering (DLS) and a micron-sized particle distribution was obtained. A series of volume fractions ( = 10–25%) were prepared from the materials in silicone oil (SO) and their sedimentation stabilities determined. The most stable composite [PIN(89%)/PE(11%)] against gravitational sedimentation was subjected to flow-rate measurements under externally applied electric field strength (E) and an electrorheological (ER) activity was observed; threshold energies (E_t) were calculated. The effects of volume fraction, shear rate, external E, frequency and temperature onto ER activities of the suspensions were investigated. Enhancement in the electric field viscosities and shear thinning viscoelastic behaviors were observed for all the samples studied. Recoverable viscoelastic deformations were determined from the creep tests under external E.     

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.