STRUCTURE RHEOLOGY OF POLYETHYLENE OXIDE SOLUTION

Intrinsic viscosities, condition for the transition from particle to network solution (critical molecular weight), viscoelastic properties, and drag reduction have been studied for polyethylene oxide in water which is widely used in industrial applications. The polyethylene oxide (PEO) samples had two different structures, the first one was linear and covers a wide range of molecular weight of (1-8000) kg/mol and the other one was branched and had molecular weights of 0.55 and 40 kg/mol.Intrinsic viscosities and Huggins constants have been determined for all types at 25ºC using a capillary viscometer. It was found that the values of Mark-Houwink parameters (K and a) increase with increasing the molecular weight for both types linear and branched  PEO. Measurements of critical molecular weight and viscoelastic properties have been carried out for the linear PEO samples in water at 25ºC using a rotational rheometer for different concentration. It was found that the critical molecular weight decreases with increasing the concentration and for the viscoelastic properties the obtained relaxation times explain the different efficiency in drag reduction for high and low molecular weight polyethylene oxide samples: only high molecular weights samples > 1000 kg/mol exhibit relaxation times high enough to be effective for vortices inhibition. Measurements of drag reduction have been carried out for the high molecular weights by using a special self-developed set-up with dimensions to obtain turbulent flow. It was found that the amount of PEO required to reduce the friction factor during the flow decreases with increasing molecular weight.