Small strain deformation measurements of konjac glucomannan solutions and the influence of borate cross-linking
Centre for Water Soluble Polymers, Glyndwr University, Plas Coch, Mold Road, Wrexham LL11 2AW, UK. Electronic address: .Carbohydrate polymers 06/2013; 95(1):272-81. DOI: 10.1016/j.carbpol.2013.02.024
The dynamic rheology of aqueous solutions of konjac glucomannan has been evaluated over a range of concentrations up to 2.35%, and the effect of borate cross-linking of such solutions evaluated in the range 0.02-40mM borate. In preliminary work, conventional parallel plate geometries were employed and in situ cross-linking was investigated. For borate cross-linked samples a superior method, however, was found to be measurement of pre-formed cores of cross-linked polymer into which a four-bladed vane geometry was introduced. In order to compare with other associating polymer systems, rheological data were analysed by defining plateau moduli, corresponding relaxation times and zero shear viscosities and the scaling behaviour of these parameters with polymer and cross-linker concentrations was established. Maxwell fits and time-concentration superposition procedures were investigated. The rheological properties of the cross-linked polymer were shown to be the result of both increased network connectivity and retarded network dynamics.
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ABSTRACT: In this paper, an approach to improve several konjac flour (KF) qualities by dimethyl sulfoxide (DMSO) addition using various concentrations at different temperature levels was proposed. Also, various properties of native and refined KF, including transparency, chemical composition and rheological properties have been investigated. The results showed that the KF refined by 75% DMSO achieved 27.7% improvement in transparency, 99.7% removal of starch, 99.4% removal of soluble sugar, and 98.2% removal of protein as well as more satisfactory viscosity stability. In addition, the morphology structure of refined KF showed a significant difference compared with the native one as observed using the SEM, which is promising for further industrial application. Furthermore, the rheological properties of both native and refined konjac sols were studied and the results showed that DMSO refinement is an effective and alternative approach to improve the qualities of KF in many aspects.
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ABSTRACT: Membrane technology has been investigated experimentally for enhanced oil recovery (EOR) in fractured rocks in this paper. Two membrane-forming material fluids, copper sulfate solution and potassium hexacyanoferrate solution, are sequentially injected into a fractured rock which was pre-saturated with mineral oil and irreducible water using a high solute fluid, to form a semi-permeable membrane over the surface of fractured rock. Then a low solute concentration fluid is injected into the rock to establish a chemical potential gradient across the membrane. As a result, water can enter the matrix across the membrane to increase the pore pressure and to displace additional oil from the matrix. Factors which influence osmotic pressure have been examined for their effect on oil recovery. It was found that the rate of oil recovery increases with increasing concentrations of membrane-forming materials, increasing temperature, and increasing solute concentration ratio between matrix water and injection solution, as well as decreasing permeability of the matrix rocks. Such correlation is attributed to the spontaneously occurrence of osmosis, leading to water entering the matrix and oil being displaced. The results are indicating that the membrane technology may be an effective EOR method for a fractured carbonate reservoir.
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