ABSTRACT:The electrorheological (ER) behavior of suspensions in silicone oil of phosphate cellulose particles (average particle size: 17.77 Jlm) was investigated at room temperature with electric fields up to 2.5kVmm-1 . For development of anhydrous ER suspensions for use at wide temperature range, it was sought the effect of the phosphate-ester reaction of celluloses on ER activity. Current density and conductivity of anhydrous ER suspensions of phosphate cellulose particles could be controlled by varying phosphoric acid concentration in phosphate-ester reactions of cellulose. When cellulose particles were treated by the phosphoric acid between 2.5 M and 3.0 M, ER suspensions containing phosphate cellulose particle electrorheological effect (r:Air: 0 ) was greatest.KEY WORDS Anhydrous Electrorheological Suspension I Phosphate-Ester Reaction of Cellulose I Electrorheological Effect ( r: Alr: 0 ) I Dielectric Constant I Current Density I Electrical Conductivity IThe influence of electric fields on the deformation and flow properties of materials has been of interest for many years. Recently, there has been renewed interest in a particular branch of these electric field effects: the electrorheological effect (ER effect). The ER effect is sometimes called the Winslow effect, after Willis Winslow who described it first. 1 Winslow found that strong electric field application to nonaqueous silica suspensions activated with a small amount of water caused rapid solidification of the originally fluid material.Rheological parameters which describe ER transition are dynamic yield stress and steady shear viscosity. Till quite recently, electrorheological fluids have been modeled as Bingham plastics. 2 -4 This means that flow is observed only after exceeding a minimum yield stress. The equation for a Bingham body is r=ry+1/pi·yWhere ry is dynamic yield stress, 1/pi plastic viscosity, and y shear rate. Application of an electric field to ER fluid, dynamic yield stress increases dramatically while plastic viscosity remains essentially unchanged. Useful characteristics of ER suspensions which show Bingham plastics are dynamic yield stress dependent upon intensity of an electric field, whose variation range is large, step less and reversible, and response time is very fast (approximately 1 ms). 5 Generally, ER suspensions which show electrorheological effect may be divided as wet-based and dry-based ER suspensions. In wet-based ER suspensions, water is a required dopant to activate the suspension. The role of water in the ER effect has remained unidentified as well as the difficulty in practical device design. One primary disadvantage of wet-based ER suspensions is the limited temperature range of usage. Presumably, viscous and conductive heating of the fluid causes the eventual loss of water result in loss of ER activity on the electric fields. 6 The presence of water leads to dielectric breakdown, corrosion and high power consumption for ER systems with substantial quantity of water. 7 Recently, aluminosilicate 8 and poly(ace...

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The electrorheological (ER) behavior of suspensions in silicone oil of phosphoric ester cellulose powder (average particle size: 17.77 µm was investigated at elevated temperatures up to 100°C. For development of anhydrous ER suspensions for use at wide temperature range, the effect of temperature on ER activity has studied. Anhydrous ER suspensions were mixed with the phosphoric ester cellulose particles made from the phosphoric ester reactions of cellulose. Durjng increasjng temperature, not only analysis of electrical properties, such as dielectric constant, current density and electrical conductivity but also rheological properties of ER suspensions were studied. Current density, conductivity and electrorheological effect (rA/7: 0) of phosphoric ester cellulose ER suspensions showed law dependence on temperature. Shear stress was closely related to the square of dielectric constant mismatch parameter (/3 2) under constant shear rate and electric field.

ABSTRACT:The electrorheological (ER) behavior of activated ER suspensions in silicone oil of phosphoric ester cellulose powder (average particle size : 17.77 µm) was investigated at room temperature with electric fields up to 2.5 kV mm −1 . For increasing ER effect of ER suspensions, activating effect of dispersed particles, phosphoric ester cellulose, on ER activity was studied. Anhydrous ER suspensions based on phosphoric ester cellulose particles made from cellulose treated in chemical solution of 2 M phosphoric acid and 4 M urea, heated at 150• C and crushed were measured.After activating the dispersed particles in anhydrous ER suspensions at 120• C, analysis of the dispersed phosphoric ester cellulose particles was made. ER properties of ER suspensions such as dielectric constant, current density, electrical conductivity, and rheological properties were studied. Activating of dispersed particles had large influence on ER activities of anhydrous ER suspensions based on phosphoric ester cellulose. With activation time, particle size, and number of dispersed particles per unit volume, electrical properties, dynamic yield stress on electric field, initial apparent viscosity (η 0 ), and ER effect (τ A /τ 0 ) of phosphoric ester cellulose ER suspensions increased at 120• C.