Freezing as a storage process for aqueous polymer solutions

There is often a need to perform rheological tests on dilute polymeric liquids at a time long after their initial preparation, for example if a more sensitive or novel method of measuring a material property (such as uniaxial/biaxial extensional viscosity or second normal-stress differences) becomes available. An inexpensive method of storing such fluids which prevents any form of deterioration (e.g. bacteriological) would therefore be of great value. This study explores the potential of freezing as that storage process by investigating whether the freeze-thaw process itself leads to rheological changes. The rheological properties of three polymeric liquids: 0.25% xanthan gum, 0.125% polyacrylamide and a 0.1%/0.1% carboxymethylcellulose/xanthan gum blend commonly used in non-Newtonian fluid flow studies were determined in both shear and oscillation before and after a freeze-thaw process. Within the uncertainty of the rheometer used, the rheological properties of the polymers studied were found to be unaffected by the freeze-thaw process leading to the conclusion that this storage method is indeed a practical possibility.