Title
Comparison of elasticity contributions during the flow of a cellulose derivative solution
Authors
MARIA BERCEA and PATRICK NAVARD

Received Dedicated to the 50^{th anniversary of Cellulose Chemistry and Technology}
Published Volume 50 Issue 5-6 May-June
Keywords rheology, elasticity, entropy, liquid crystal, blend, hydroxypropylcellulose

Abstract
Three contributions to elasticity (chain entropic contribution, orientational distortion of the director of a nematic phase, interfacial tension) in viscoelastic fluids are compared experimentally using hydroxypropylcellulose (HPC) solutions in water. Elasticity is assessed by measuring the elastic recovery after a simple shear. The entropic contribution to elasticity is measured after shearing an isotropic concentrated solution. The contribution of orientational distortions of the director of a nematic phase to elasticity is measured on HPC-water solutions with HPC concentrations above the isotropic-nematic (or twisted nematic) concentration. Finally, an incompatible blend of HPC-water and polydimethylsiloxane is used to measure the elastic contribution due to an increase of interfacial area. Results show that by far, the elastic recovery of the distortion of a nematic director is much higher than the contribution of the entropic elasticity.