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Structure-property relationships in ...

Barry, Carol Forance.

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Structure-property relationships in electrorheological fluids.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Structure-property relationships in electrorheological fluids./
作者:	Barry, Carol Forance.
出版者:	Ann Arbor : ProQuest Dissertations & Theses, : 1996,
面頁冊數:	134 p.
附註:	Source: Dissertations Abstracts International, Volume: 58-02, Section: B.
Contained By:	Dissertations Abstracts International58-02B.
標題:	Polymers. -
電子資源:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=9625454
ISBN:	9798684697753

Structure-property relationships in electrorheological fluids.
Barry, Carol Forance.

Structure-property relationships in electrorheological fluids. - Ann Arbor : ProQuest Dissertations & Theses, 1996 - 134 p.

Source: Dissertations Abstracts International, Volume: 58-02, Section: B.

Thesis (D.Eng.)--University of Massachusetts Lowell, 1996.

Electrorheological (ER) behavior of three families of ER fluids were experimentally evaluated in forced dynamic shear. Each of these families were identified by differences in their dispersed phase with suspending fluid, either chlorinated paraffin or mineral oil, held constant. The three dispersed phases considered were biopolymers, ceramic powders, and arylamino phosphazenes. In each case, the structure of the dispersed phase was varied in a systematic fashion and the impact on ER performance experimentally quantified. The ceramic and phosphazene powders, and most of the biopolymers exhibited ER activity when tested as suspensions in chlorinated paraffin or mineral oil. However, the phosphazene powders had a third of the response of the other two systems. This was attributed to the poor mobility of the arylamino side chains in the viscous oils or their overabundance. The ER activity of the anhydrous ceramic powders consistently scaled with field strength. In contrast, the field sensitivity of the biopolymers varied with water content. The first order relationship was consistent with the expected value for an ER fluid developed from strongly interacting particles such as occurred between the oil and the ceramic particles while quadratic dependence was expected for lightly hydrated biopolymers. However, anhydrous or nearly anhydrous particles produced the more common parabolic response of complex viscosity to increasing field strength. Although some biopolymer systems retained this response, others exhibited a sigmoidal response when highly hydrated. While sigmoidal responses have been occasionally reported in the literature, this work suggested that all hydrated ER fluids eventually saturate, and that the sigmoidal response was apparently caused by saturation polarization of the fluids. The storage moduli, loss moduli and complex viscosities of all systems decreased with increasing strain amplitude. These systems produced power law dependencies of 0 to 2.0. Since the dependence generally increased with the strength of the ER fluid, the power law exponents increased with field strength and correlated well with the field strength dependencies of the polymers. This ER fluid response to strain amplitude was typical of concentration suspensions. As seen in previous research, the ER effect of the biopolymers was independent of particle size. A limited study with the ceramic powders showed that larger agglomerates produced somewhat reduced ER activity. This was attributed to the ceramics' high dielectric constants which create agglomerates that are difficult to fracture in normal measurement. Increased particulate loadings produced exponential increases in the ER response of all measured systems. While these effects in the ferroelectric ceramic powders usually correlated with previous observations, those in paraelectric barium titanate and the highly hydrated biopolymer systems were greater than or reversed previously observed trends. The electrorheological response of the biopolymers was highly dependent on molecular weight, and moisture content of the dispersed phase. Within analogous series of polymers, the ER effect decreased as a power law function of weight-average molecular weight. The difference between these series was due to the water uptake and charge of the polymers. Since the ionic contribution to the ER effect most likely overrode other contributions in relatively anhydrous anionic polysaccharides, ionic polymers were less sensitive to molecular weight. (Abstract shortened by UMI.).

ISBN: 9798684697753Subjects--Topical Terms:

535398
Polymers.
Subjects--Index Terms:

polysaccharides

Structure-property relationships in electrorheological fluids.
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520 $a Electrorheological (ER) behavior of three families of ER fluids were experimentally evaluated in forced dynamic shear. Each of these families were identified by differences in their dispersed phase with suspending fluid, either chlorinated paraffin or mineral oil, held constant. The three dispersed phases considered were biopolymers, ceramic powders, and arylamino phosphazenes. In each case, the structure of the dispersed phase was varied in a systematic fashion and the impact on ER performance experimentally quantified. The ceramic and phosphazene powders, and most of the biopolymers exhibited ER activity when tested as suspensions in chlorinated paraffin or mineral oil. However, the phosphazene powders had a third of the response of the other two systems. This was attributed to the poor mobility of the arylamino side chains in the viscous oils or their overabundance. The ER activity of the anhydrous ceramic powders consistently scaled with field strength. In contrast, the field sensitivity of the biopolymers varied with water content. The first order relationship was consistent with the expected value for an ER fluid developed from strongly interacting particles such as occurred between the oil and the ceramic particles while quadratic dependence was expected for lightly hydrated biopolymers. However, anhydrous or nearly anhydrous particles produced the more common parabolic response of complex viscosity to increasing field strength. Although some biopolymer systems retained this response, others exhibited a sigmoidal response when highly hydrated. While sigmoidal responses have been occasionally reported in the literature, this work suggested that all hydrated ER fluids eventually saturate, and that the sigmoidal response was apparently caused by saturation polarization of the fluids. The storage moduli, loss moduli and complex viscosities of all systems decreased with increasing strain amplitude. These systems produced power law dependencies of 0 to 2.0. Since the dependence generally increased with the strength of the ER fluid, the power law exponents increased with field strength and correlated well with the field strength dependencies of the polymers. This ER fluid response to strain amplitude was typical of concentration suspensions. As seen in previous research, the ER effect of the biopolymers was independent of particle size. A limited study with the ceramic powders showed that larger agglomerates produced somewhat reduced ER activity. This was attributed to the ceramics' high dielectric constants which create agglomerates that are difficult to fracture in normal measurement. Increased particulate loadings produced exponential increases in the ER response of all measured systems. While these effects in the ferroelectric ceramic powders usually correlated with previous observations, those in paraelectric barium titanate and the highly hydrated biopolymer systems were greater than or reversed previously observed trends. The electrorheological response of the biopolymers was highly dependent on molecular weight, and moisture content of the dispersed phase. Within analogous series of polymers, the ER effect decreased as a power law function of weight-average molecular weight. The difference between these series was due to the water uptake and charge of the polymers. Since the ionic contribution to the ER effect most likely overrode other contributions in relatively anhydrous anionic polysaccharides, ionic polymers were less sensitive to molecular weight. (Abstract shortened by UMI.).
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