ABSTRACT
I. INTRODUCTION The shear flow of polymer solutions. both dilute and concentrated. and employing either water or an organic liquid as the solvent. is encountered in a wide variety of technologically important situations. Common examples include the addition of 2-3% of a polymer such as polymethyl methacrylate to a mineral oil in order to formulate multigrade motor oils: the polymer serves to reduce the dependence of oil viscosity on temperature and also to lower the pour point. More concentrated solutions. containing up to 30% or 40% polymer. are used to manufacture textile fibers by the process of (wet or dry) solution spinning. This is because, though polymers such as cellulose acetate cannot be melted. they can be dissolved in a solvent such as acetic acid or acetone. ln the petroleum industry. aqueous solutions of xanthan gum polysaccharides and partially hydrolyzed polyacrylamides in a concentration range of a few hundreds of ppm are utilized for enhanced oil recovery by water flooding: the thickening effect of the added polymer reduces the mobility difference between the injected water and the oil in place, thereby improving both areal and vertical sweep efficiencies. The thickening effect of polymers is also put to good use in the food industry. where xanthan gum is a common additive in salad dressings and other products. Paints and coatings are other applications of polymer solutions. Note that high-molecular-weight polymers can be fairly shear sensitive. and chain scission takes place quite easily. It is for this reason that. to achieve a desired enhancement in viscosity. one often adds a large amount of low-molecular-weight polymer instead of a small amount
of high-molecular-weight polymer to a solvent if large deformation rates are likely to be encountered.
