Flow properties of aqueous solution of methylcellulose

Abstract

AbstractFlow properties of aqueous solution of methylcellulose, especially nonlinear viscoelasticity, were investigated. The peculiar flow properties of the aqueous solution of methylcellulose were compared with the existing theories of non‐Newtonian viscosity of concentrated polymer solutions and the experimental results obtained for the aqueous solution of sodium alginate which behaves as polyelectrolyte in solution. The characteristic time for the formation of entanglement couplings between molecular chains was mainly examined. To investigate the elastic behavior under steady‐shear flow, normal stress difference was measured with a coaxial cylinder apparatus, and extinction angles were determined with a flow birefringence apparatus. The values of normal stress difference obtained by the mechanical and the optical methods coincided with each other. For the aqueous solution of methylcellulose as reported for solutions of nonpolar polymers, the relation between normal stress difference and shear stress was represented by a single curve irrespective of temperature and concentration. Non‐Hooken behavior was observed for the relation between recoverable shear and shear stress and attributed to the strong intermolecular interactions and the stretching‐out effect of structural networks.