Drag Reducing Properties of Polyphosphates

Abstract

It is well known that small amounts of certain polymers of high molecular weight can substantially reduce the frictional losses in liquids during turbulent flow1,2. In capillaries3 the reduction can reach 50% or more at concentrations well below 100 parts per million by weight (p.p.m.w.). This effect has been observed with a wide range of organic materials, both of natural and synthetic origins. Although there is no completely satisfactory explanation for this phenomenon, there are a number of characteristics which most good drag reducing agents seem to have in common—for example, the presence of pronounced viscoelasticity even at very low concentrations, a few hundredths of a per cent4. As a result the presence of viscoelasticity may indicate potential drag reducing ability. In this connection a series of solutions was recently tested in our laboratory and it was observed that a dilute solution of potassium polyphosphate was highly viscoelastic. The solution exhibited a large recoil on cessation of stirring even at very low stirring rates. Furthermore, the shear viscosity showed a strong reversible dependence on shear rate. Consequently, it was decided to test for drag reducing ability.