PREPARATION AND VISCOSITY BEHAVIOR OF HYDROPHOBICALLY-MODIFIED POLY(VINYL ALCOHOL) (PVA)

In this study, a novel series of water-soluble hydrophobically modifie d poly(vinyl alcohol) (PVA) is prepared by chemical modification of PV A, with the objective of investigating the polymer's theological behav ior for enhanced oil recovery applications. The solution viscosity of the polymer obtained is studied with respect to the polymer concentrat ion, temperature, salinity, polymer modification, aging, shear rate, a nd polymer molecular weight. The solution viscosity of the PVA is grea tly enhanced by the modification. The modified PVA exhibits a relative ly high salt tolerance, typical of nonionic polymers, in the range of 0-7.0 wt % NaCl concentrations, and the viscosity of the polymer solut ion is relatively invariant with NaCl above 3.0 wt % NaCl concentratio n. Below 3 wt %, the viscosity shows a maximum then a minimum, an unus ual behavior. Generally, the polymer exhibits an almost constant visco sity at high shear rates and a typical shear thinning behavior at low shear rates. In addition, increasing polymer concentration and molecul ar weight leads to an increase in the polymer solution viscosity. More over, the polymer exhibits smaller solution viscosity at a high temper ature, and a slight decrease in viscosity is also exhibited by the mod ified polymer with aging. Comparison of the viscosities of 18 polymer modifications indicates that the larger the numbers of hydrophobic gro ups (side chains) in the polymer structure, the smaller the viscosity. Moreover, the longer the hydrophobic groups (side chains) in the poly mer structure, the greater the viscosity, if their number is small. (C ) 1995 John Wiley & Sons, Inc.