Shear thickening implies that the viscosity of a fluid increases with increasing rates of shear. In the past work reported, all shear thickening phenomena were observed in concentrated solid/liquid colloidal suspensio...Shear thickening implies that the viscosity of a fluid increases with increasing rates of shear. In the past work reported, all shear thickening phenomena were observed in concentrated solid/liquid colloidal suspension. In this paper, the shear thickening was observed in colloidal dispersion gel, with very lower volume fraction, of partially hydrolyzed polyacrylamide(PHPA)/aluminum citrate. Colloidal dispersion gels are made of low concentrations of polymer and crosslinker. Polymer mass fractions normally range from 0.01% to 0.12%. In this concentration regime, there is not enough polymer to form a continuous network, so a conventional bulk type gel cannot form. Instead of a solution of separate gel bundles forms, and it is a mixture of predominantly intramolecular and minimal intermolecular crosslinks. In the work reported here, the colloidal dispersion gels are made of PHPA of 0 03%, KCl of 0.5%, thiourea of 0.1% and Al 3+ with a mass fractions range of 0—0 003%, the Al 3+ ∶PHPA mass ratio changes from 0 to 0.1. The critical shear rates(CSR) for the onset of shear thickening are about 200 s -1 for all CDG systems studied, i.e ., the Al 3+ ∶PHPA mass ratio don’t affect the CSR. In the lower shear regime than CSR shear thinning was observed and in the higher shear regime than CSR the shear thickening was observed. The shear thickening may be explained with cluster formation mechanism.展开更多
In this paper the crosslinking reaction between partially hydrolyzed Polyacrylamide (HPAM) with ultrahigh molecular weight and chromium (Ⅲ) was investigated by atomic absorption method. The results showed that when t...In this paper the crosslinking reaction between partially hydrolyzed Polyacrylamide (HPAM) with ultrahigh molecular weight and chromium (Ⅲ) was investigated by atomic absorption method. The results showed that when the concentration of HPAM was fixed , the crosslinking density decreased with the increase of n (COO -)/ n . When the amount of Cr(Ⅲ) was fixed, the crosslinking density increased with the increase of n (COO -)/ n . When the initial pH value of HPAM/Cr(Ⅲ) system was between 4 and 8, the crosslinking density increased with the increase of pH value. The crosslinking density also increased with the increase of temperature and the increase of salinity.展开更多
文摘Shear thickening implies that the viscosity of a fluid increases with increasing rates of shear. In the past work reported, all shear thickening phenomena were observed in concentrated solid/liquid colloidal suspension. In this paper, the shear thickening was observed in colloidal dispersion gel, with very lower volume fraction, of partially hydrolyzed polyacrylamide(PHPA)/aluminum citrate. Colloidal dispersion gels are made of low concentrations of polymer and crosslinker. Polymer mass fractions normally range from 0.01% to 0.12%. In this concentration regime, there is not enough polymer to form a continuous network, so a conventional bulk type gel cannot form. Instead of a solution of separate gel bundles forms, and it is a mixture of predominantly intramolecular and minimal intermolecular crosslinks. In the work reported here, the colloidal dispersion gels are made of PHPA of 0 03%, KCl of 0.5%, thiourea of 0.1% and Al 3+ with a mass fractions range of 0—0 003%, the Al 3+ ∶PHPA mass ratio changes from 0 to 0.1. The critical shear rates(CSR) for the onset of shear thickening are about 200 s -1 for all CDG systems studied, i.e ., the Al 3+ ∶PHPA mass ratio don’t affect the CSR. In the lower shear regime than CSR shear thinning was observed and in the higher shear regime than CSR the shear thickening was observed. The shear thickening may be explained with cluster formation mechanism.
文摘In this paper the crosslinking reaction between partially hydrolyzed Polyacrylamide (HPAM) with ultrahigh molecular weight and chromium (Ⅲ) was investigated by atomic absorption method. The results showed that when the concentration of HPAM was fixed , the crosslinking density decreased with the increase of n (COO -)/ n . When the amount of Cr(Ⅲ) was fixed, the crosslinking density increased with the increase of n (COO -)/ n . When the initial pH value of HPAM/Cr(Ⅲ) system was between 4 and 8, the crosslinking density increased with the increase of pH value. The crosslinking density also increased with the increase of temperature and the increase of salinity.
