What is the difference between absolute and apparent viscosity?ĭynamic (absolute) viscosity: Dynamic viscosity is also known as absolute viscosity and most often relates to non-Newtonian fluids. will be shown to be a unique function of molecular weight (for a given polymer-solvent pair) and measurements of can be used to measure molecular weight. Specific viscosity expresses the incremental viscosity due to the presence of the polymer in the solution. It can be calculated by dividing shear stress by shear rate. In Newtonian fluids, this value doesn’t change, but with non-Newtonian fluids, apparent viscosity is directly affected by the shear rate. How do you calculate apparent viscosity?Īpparent (shear) viscosity: Apparent, or shear, viscosity refers to the relationship between viscosity and shear rate. structure builds up, again when the shear rate is eliminated or reduced. The reversibility of the process results that the viscosity recovers, i.e. Thixotropy is a reversible, isothermal, time-dependent decrease in the apparent viscosity when a material is subjected to increased shear rate (Mewis, 1979). Why should apparent viscosity decrease in thixotropy? Apparent (shear) viscosity: Apparent, or shear, viscosity refers to the relationship between viscosity and shear rate. It can be defined as the ratio of dynamic viscosity to density. What is the difference between apparent viscosity and viscosity? Intrinsic viscosity is determined by measuring the relative viscosity at several different concentrations and then extrapolating the specific viscosity to zero concentration. The intrinsic viscosity number is defined as the limiting value of the specific viscosity/concentration ratio at zero concentration. How is intrinsic viscosity related to relative viscosity? The formula for Relative Viscosity is: ηr = η / ηs. The relative viscosity if the ration of the viscosity of a solution (η) to the viscosity of the solvent (ηs) in that solution. For a Newtonian fluid, the apparent viscosity is constant, and equal to the Newtonian viscosity of the fluid, but for non-Newtonian fluids, the apparent viscosity depends on the shear rate. 7 How does the relative viscosity of a solution change?Īpparent viscosity (sometimes denoted η) is the shear stress applied to a fluid divided by the shear rate ( ).6 Is the apparent viscosity of a fluid constant?.5 What is the relationship between dynamic and kinematic viscosity?.4 How do you calculate apparent viscosity?.3 Why should apparent viscosity decrease in thixotropy?.

Apparent viscosity formula