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Lu Zhang - One of the best experts on this subject based on the ideXlab platform.
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effect of branched chain and polyoxyethylene group on surface dilational rheology of cationic surfactants
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2019Co-Authors: Zenglin Wang, Lei Zhang, Qingtao Gong, Tao Wang, Zhicheng Xu, Lu ZhangAbstract:Abstract The measurements of dynamic surface tensions and surface dilational rheological properties were carried out for four cationic surfactants aqueous solutions, hexadecanol glycidyl ether ammonium chloride (C16PC), guerbet alcohol hexadecyl glycidyl ether ammonium chloride (C16GPC), hexadecanol polyoxyethylene(3) glycidyl ether ammonium chloride(C16(EO)3PC) and guerbet alcohol hexadecyl polyoxyethylene(3) glycidyl ether ammonium chloride (C16G(EO)3PC), using the oscillating bubble method. The influences of surface ageing time, surface pressure, dilational frequency and Bulk Concentration on surface rheological properties have been expounded. It is found that diffusion-exchange process plays the crucial role for C16PC film at all experimental Concentrations. On the other hand, the relaxation process in-surface dominates the properties of film at low and high Bulk Concentration for branched cationic surfactants and C16(EO)3PC respectively. The branched hydrophobic chain will enhanced the molecular interactions at the surface and improve the value of modulus maximum. The introducing of EO group will produce new relaxation process, such as the variation of orientation of EO group at the surface, which enhances the contributions of viscous nature of film. Moreover, the coexistence of branched chain and EO group will produce oriented variations of film structure and result in the maximum modulus at dynamic curve.
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wettability of a polymethylmethacrylate surface in the presence of benzyl substituted alkyl betaines
Journal of Molecular Liquids, 2019Co-Authors: Qun Zhang, Lei Zhang, Lu Zhang, Zhaohui Zhou, Xinyu Zhou, Lu HanAbstract:Abstract The adsorption and wettability of benzyl substituted alkyl carboxylbetaine (BCB) and alkyl sulfobetaine (BSB) at polymethylmethacrylate (PMMA) surfaces have been studied by contact angle measurements and the adsorption parameters such as adhesional tension, adsorption amount, work of adhesion and PMMA-liquid interfacial tension (γSL) have been calculated. The results show that the values of contact angle of betaines keep constant before CMC, which can be explained well by the compensation effect of the decrease of surface tension and increase of γSL with an increase of Bulk Concentration. However, only the contact angle of BCB solution begins to decline when the Concentration is far higher than CMC, indicating the re-adsorption. Both the hydrophilic head and benzyl of BCB molecules interact with PMMA surface, which decreases adsorption amount but improves ability of hydrophobic modification for PMMA. On the other hand, the benzyl may trend to stretch towards aqueous for BSB, instead of interacting with PMMA, because of the steric effect of larger hydrophilic head of BSB. The unique arrangement of BSB molecules at PMMA surface makes it difficult to re-adsorb onto monolayer at higher Bulk Concentration.
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dynamic interfacial tensions of alkyl alcohol polyoxypropylene oxyehtylene ether sulfonate solutions
Journal of Petroleum Science and Engineering, 2016Co-Authors: Long Guo, Lei Zhang, Yan Liu, Qingtao Gong, Lu ZhangAbstract:Abstract The dynamic interfacial tensions (IFTs) of a series of branched alkyl ether sulfonates with different number of ethylene oxide (EO) groups and propylene oxide (PO) groups, C 8 PO 3 EO 3 S, C 8 PO 3 EO 6 S, C 8 PO 6 EO 3 S and C 8 PO 6 EO 6 S, against n-alkane have been investigated by spinning drop interfacial tensiometer. The influences of surfactant Concentration and salinity on IFT were expounded. The effect of alkyl chain carbon number (ACN) of the oil phase on the IFT has also been investigated. The experimental results show that the dynamic IFTs of C 8 PO 3 EO 6 S and C 8 PO 6 EO 3 S decrease and then reach a plateau with time, shown as an L-shaped; on the other hand, the dynamic IFTs go through minima and show V-shaped for C 8 PO 3 EO 3 S and C 8 PO 6 EO 6 S solutions at high Bulk Concentration. Moreover, V-shaped curve also appears at low Bulk Concentration for C 8 PO 3 EO 3 S and C 8 PO 6 EO 6 S with addition of NaCl. An increase in the length of alky chain of the oil molecules will enhance V-shaped phenomenon as well. This research suggests that the ratio of PO groups to EO groups is a key factor for controlling interfacial properties. Under optimal conditions, the transient and equilibrium ultralow IFTs can be obtained by C 8 PO 6 EO 6 S and C 8 PO 6 EO 3 S solutions respectively. Previous studies have shown that the interfacial Concentration of surfactant monomers and the cross-sectional area of surfactant molecule at the interface are the two most important factors in dominating ultralow IFT. A mechanism base on the variation of cross-sectional area of surfactant molecule due to the PO groups looping away from the aqueous phase into the oil phase has been provided for understanding the ultralow IFT property for anionic–nonionic surfactants.
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effect of gum arabic on the surface tension and surface dilational rheology of trisiloxane surfactant
Food Hydrocolloids, 2013Co-Authors: Chong Cao, Lu Zhang, Xiaoxi ZhangAbstract:Abstract The surface tension and surface dilational properties of trisiloxane surfactant silwet408, gum arabic, and their mixed solutions are reported. The dilational rheological properties are measured by means of oscillating drop method. The influences of dilational frequency, Bulk Concentration and aging time on dilational rheology properties have been investigated. The adsorption films of silwet408 behave elastic in nature at low Bulk Concentration. With increasing Concentration, the dilational modulus becomes more frequency dependent and reaches a maximum value. The addition of 1 wt% gum arabic has no remarkable influence on the silwet408 films since the adsorption ability of silwet408 is much better than that of gum arabic. However, the maximum of dilational modulus and dilational elasticity are shifted toward a higher Concentration, which has been correlated with the decreased molecular exchange in the presence of 1 wt% gum arabic.
Misni Misran - One of the best experts on this subject based on the ideXlab platform.
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rheology properties of glucopyranoside stabilized oil water emulsions effect of alkyl chain length and Bulk Concentration of the surfactant
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004Co-Authors: Boris B Niraula, Tan Cok King, Tham Kok Chun, Misni MisranAbstract:Abstract Effect of the alkyl chain length and Concentration of the surfactant on Rheology properties of O/W emulsions stabilized with homologues series of glucopyranoside was studied. The Rheology properties in turn are being used to describe emulsion structure, emulsifying effect and emulsion stability. The emulsifying property was also explored through interfacial tension measurement. The homologues series of glucopyranoside possess identical polar head group structure, whereas the alkyl chain length varied from C7 to C10. The O/W emulsions were prepared by mixing 0.8 volume fractions of oil phase into a much smaller volume fraction of water phase; in this case 0.2 volume fractions of aqueous surfactant solution. Given energy input during emulsification and Bulk surfactant Concentration kept constant, the given oil to water mixing ratio would give high internal phase ratio concentrated O/W emulsions with dispersed phase volume fraction of ≈0.8, whereas the average size of the droplets was varied with the variation of both the alkyl length and the surfactant Concentration. The average droplet size decreased with increasing both the length of the alkyl tail and the Bulk Concentration of the surfactant, so did interfacial free energy and cmc. As expected the Rheology properties of these emulsion samples depended strongly on average droplet size of the dispersed phase. The steady shear Rheology properties, such as shear viscosity, degree of shear thinning and σy enhanced with the decrease in average droplet size. This implies that not only the size of the emulsion droplets decreased with increasing both the length of the alkyl tail and Bulk Concentration of the surfactant, but also the emulsion and its storage stability were improved and enhanced with the increase in these two factors. Likewise, in the oscillatory shear mode the degree of viscoelasticity also depended on average droplet size. The fact that the G ′ ≫ G ″ , it is evident that the elastic property is dominant in these emulsions over viscous property. As expected the degree of elasticity enhanced with decreasing average droplet size of the dispersed phase. The G ′ ( ω ) ≫ G ″ ( ω ) at all measured ω, but the G′(ω2) function was found to be linear whereas the G″(ω) functions was independent, indicating that the oscillatory shear property of these emulsions can not be adequately described by Maxwell type viscoelastic model. Also, the fact that, δ of these emulsions was much smaller than 45° at all measured oscillatory ω, it is evident that elastic property of these emulsions dominated their viscous property. δ of these emulsions decreased strongly with decreasing droplet size, further implying that the degree of elasticity of these emulsions enhanced and improved with decreasing average droplets size.
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evaluation of rheology property of dodecyl maltoside sucrose dodecanoate brij 35p and sds stabilized o w emulsion effect of head group structure on rheology property and emulsion stability
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004Co-Authors: Boris B Niraula, Tan Cok King, Misni MisranAbstract:Emulsifying property of four emulsifiers is being explored and compared using tensiometry and Rheology. These emulsifiers possess same number of carbon in their alkyl tail (C12 in this case), but differ in their head group structure. The head group structure of these emulsifiers are maltose, sucrose, ethylene oxide and sulphate; providing a homologue series whose head group polarity and therewith HLB values differ significantly from each other. While aqueous emulsifier solutions of varying Concentration were used as water phase, paraffin oil was used as oil phase. The oil to water mixing ratio used was 8:2. This naturally gave rise to high internal phase concentrated oil-in-water (O/W) emulsions with dispersed phase volume fractions of ≈0.8, in which the dispersed droplets are organized to give a densely packed polyhedron configuration as described by Princen. Such concentrated emulsions would exhibit interesting Rheology properties including shear-thinning behavior and viscoelastic effects. Given all other factors such as procession conditions (energy input through shearing and shearing time), volume fraction of the dispersed phase and viscosity of the continuous phase kept constant, the given mixing ratio would yield oil-in-water emulsions whose droplet size distribution and polydispersity index depended strongly on HLB value of the emulsifier used for their emulsification. The Rheology properties of such emulsions strongly depended on the average size distribution of the dispersed droplets that could be varied both with the Bulk Concentration and HLB value of the emulsifier. The interfacial and surface properties of these surfactants suggest that the droplet size distribution of the dispersed phase is strongly related to the HLB value and Bulk Concentration of the emulsifier used. Hence, it is evident that the Rheology properties of such emulsions vary strongly both with the HLB value and Bulk Concentration of the emulsifier. That is why the Rheology properties can be employed to describe both the emulsifying effect of the emulsifier and the storage stability of the resulting emulsion. As expected, the emulsifying effect of the emulsifier, the structure of the resulting emulsions and their storage stability depended strongly on HLB value of the emulsifier. As identified by yield stress, shear viscosity and storage modulus, both the degree of emulsification and storage stability enhanced with decreasing droplet size of the dispersed phase, and decreased with decreasing HLB value of the emulsifier used. Both the emulsifying effect and emulsion stability further were enhanced with increasing emulsifier Concentration.
Reghan J. Hill - One of the best experts on this subject based on the ideXlab platform.
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Transport in polymer-gel composites: response to a Bulk Concentration gradient.
The Journal of Chemical Physics, 2006Co-Authors: Reghan J. HillAbstract:This paper examines the response of electrolyte-saturated polymer gels, embedded with charged spherical inclusions, to a weak gradient of electrolyte Concentration. An electrokinetic model was presented in an earlier publication, and the response of homogeneous composites to a weak electric field was calculated. In this work, the influence of the inclusions on Bulk ion fluxes and the strength of an electric field (or membrane diffusion potential) induced by the Bulk electrolyte Concentration gradient are computed. Effective ion diffusion coefficients are significantly altered by the inclusions, so—depending on the inclusion surface charge or ζ potential—asymmetric electrolytes can behave as symmetrical electrolytes and vice versa. The theory also quantifies the strength of flow driven by Concentration-gradient-induced perturbations to the equilibrium diffuse double layers. Similarly to diffusiophoresis, the flow may be either up or down the applied Concentration gradient.
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transport in polymer gel composites response to a Bulk Concentration gradient
arXiv: Soft Condensed Matter, 2005Co-Authors: Reghan J. HillAbstract:This paper examines the response of electrolyte-saturated polymer gels, embedded with charged spherical inclusions, to a weak gradient of electrolyte Concentration. These composites present a model system to study microscale electrokinetic transport processes, and a rigorous theoretical prediction of the Bulk properties will benefit novel diagnostic applications. An electrokinetic model was presented in an earlier publication, and the response of homogeneous composites to a weak electric field was calculated. In this work, the influence of the inclusions on Bulk ion fluxes and the strength of an electric field (or membrane diffusion potential) induced by the Bulk electrolyte Concentration gradient are computed. Effective ion diffusion coefficients are significantly altered by the inclusions, so--depending on the inclusion surface charge or $\zeta$-potential--asymmetric electrolytes can behave as symmetrical electrolytes, and vice versa. The theory also quantifies the strength of flow driven by Concentration-gradient-induced perturbations to the equilibrium diffuse double layers. Similarly to diffusiophoresis, the flow may be either up or down the applied Concentration gradient.
Boris B Niraula - One of the best experts on this subject based on the ideXlab platform.
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rheology properties of glucopyranoside stabilized oil water emulsions effect of alkyl chain length and Bulk Concentration of the surfactant
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004Co-Authors: Boris B Niraula, Tan Cok King, Tham Kok Chun, Misni MisranAbstract:Abstract Effect of the alkyl chain length and Concentration of the surfactant on Rheology properties of O/W emulsions stabilized with homologues series of glucopyranoside was studied. The Rheology properties in turn are being used to describe emulsion structure, emulsifying effect and emulsion stability. The emulsifying property was also explored through interfacial tension measurement. The homologues series of glucopyranoside possess identical polar head group structure, whereas the alkyl chain length varied from C7 to C10. The O/W emulsions were prepared by mixing 0.8 volume fractions of oil phase into a much smaller volume fraction of water phase; in this case 0.2 volume fractions of aqueous surfactant solution. Given energy input during emulsification and Bulk surfactant Concentration kept constant, the given oil to water mixing ratio would give high internal phase ratio concentrated O/W emulsions with dispersed phase volume fraction of ≈0.8, whereas the average size of the droplets was varied with the variation of both the alkyl length and the surfactant Concentration. The average droplet size decreased with increasing both the length of the alkyl tail and the Bulk Concentration of the surfactant, so did interfacial free energy and cmc. As expected the Rheology properties of these emulsion samples depended strongly on average droplet size of the dispersed phase. The steady shear Rheology properties, such as shear viscosity, degree of shear thinning and σy enhanced with the decrease in average droplet size. This implies that not only the size of the emulsion droplets decreased with increasing both the length of the alkyl tail and Bulk Concentration of the surfactant, but also the emulsion and its storage stability were improved and enhanced with the increase in these two factors. Likewise, in the oscillatory shear mode the degree of viscoelasticity also depended on average droplet size. The fact that the G ′ ≫ G ″ , it is evident that the elastic property is dominant in these emulsions over viscous property. As expected the degree of elasticity enhanced with decreasing average droplet size of the dispersed phase. The G ′ ( ω ) ≫ G ″ ( ω ) at all measured ω, but the G′(ω2) function was found to be linear whereas the G″(ω) functions was independent, indicating that the oscillatory shear property of these emulsions can not be adequately described by Maxwell type viscoelastic model. Also, the fact that, δ of these emulsions was much smaller than 45° at all measured oscillatory ω, it is evident that elastic property of these emulsions dominated their viscous property. δ of these emulsions decreased strongly with decreasing droplet size, further implying that the degree of elasticity of these emulsions enhanced and improved with decreasing average droplets size.
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evaluation of rheology property of dodecyl maltoside sucrose dodecanoate brij 35p and sds stabilized o w emulsion effect of head group structure on rheology property and emulsion stability
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2004Co-Authors: Boris B Niraula, Tan Cok King, Misni MisranAbstract:Emulsifying property of four emulsifiers is being explored and compared using tensiometry and Rheology. These emulsifiers possess same number of carbon in their alkyl tail (C12 in this case), but differ in their head group structure. The head group structure of these emulsifiers are maltose, sucrose, ethylene oxide and sulphate; providing a homologue series whose head group polarity and therewith HLB values differ significantly from each other. While aqueous emulsifier solutions of varying Concentration were used as water phase, paraffin oil was used as oil phase. The oil to water mixing ratio used was 8:2. This naturally gave rise to high internal phase concentrated oil-in-water (O/W) emulsions with dispersed phase volume fractions of ≈0.8, in which the dispersed droplets are organized to give a densely packed polyhedron configuration as described by Princen. Such concentrated emulsions would exhibit interesting Rheology properties including shear-thinning behavior and viscoelastic effects. Given all other factors such as procession conditions (energy input through shearing and shearing time), volume fraction of the dispersed phase and viscosity of the continuous phase kept constant, the given mixing ratio would yield oil-in-water emulsions whose droplet size distribution and polydispersity index depended strongly on HLB value of the emulsifier used for their emulsification. The Rheology properties of such emulsions strongly depended on the average size distribution of the dispersed droplets that could be varied both with the Bulk Concentration and HLB value of the emulsifier. The interfacial and surface properties of these surfactants suggest that the droplet size distribution of the dispersed phase is strongly related to the HLB value and Bulk Concentration of the emulsifier used. Hence, it is evident that the Rheology properties of such emulsions vary strongly both with the HLB value and Bulk Concentration of the emulsifier. That is why the Rheology properties can be employed to describe both the emulsifying effect of the emulsifier and the storage stability of the resulting emulsion. As expected, the emulsifying effect of the emulsifier, the structure of the resulting emulsions and their storage stability depended strongly on HLB value of the emulsifier. As identified by yield stress, shear viscosity and storage modulus, both the degree of emulsification and storage stability enhanced with decreasing droplet size of the dispersed phase, and decreased with decreasing HLB value of the emulsifier used. Both the emulsifying effect and emulsion stability further were enhanced with increasing emulsifier Concentration.
Xiaoxi Zhang - One of the best experts on this subject based on the ideXlab platform.
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effect of gum arabic on the surface tension and surface dilational rheology of trisiloxane surfactant
Food Hydrocolloids, 2013Co-Authors: Chong Cao, Lu Zhang, Xiaoxi ZhangAbstract:Abstract The surface tension and surface dilational properties of trisiloxane surfactant silwet408, gum arabic, and their mixed solutions are reported. The dilational rheological properties are measured by means of oscillating drop method. The influences of dilational frequency, Bulk Concentration and aging time on dilational rheology properties have been investigated. The adsorption films of silwet408 behave elastic in nature at low Bulk Concentration. With increasing Concentration, the dilational modulus becomes more frequency dependent and reaches a maximum value. The addition of 1 wt% gum arabic has no remarkable influence on the silwet408 films since the adsorption ability of silwet408 is much better than that of gum arabic. However, the maximum of dilational modulus and dilational elasticity are shifted toward a higher Concentration, which has been correlated with the decreased molecular exchange in the presence of 1 wt% gum arabic.
