Rheological properties of hydroxypropylmethyl cellulose/sodium dodecylsulfate mixtures

Abstract

The rheological properties of mixtures of hydroxypropylmethyl cellulose (HPMC), a nonionic associative cellulose ether, and sodium dodecylsulfate (SDS), an anionic surfactant, were investigated by viscosity measurements performed at different shear rates (0.1-6000 s-1). HPMC/SDS mixtures containing different concentrations of SDS (cSDS, 0.00-3.50 mass %) and HPMC concentrations, which corresponded to the overlap parameter c/c * of 3, 6 and 12, were prepared. All HPMC/SDS mixtures were found to be shear-thinning when examined in the low-end to mid-range of the applied shear rates. The degree of shear-thinning, n, and the viscosity of the mixtures were influenced by composition of the HPMC/SDS mixtures and HPMC-SDS complex formation. The changes in n ranged from values typical for highly shear-thinning to almost perfectly Newtonian liquids, and were more pronounced as c/c* was increased from 3 to 6 and 12. A change in the flow profile and a buildup of the first normal stress difference (N1) was observed in HPMC/SDS mixtures with c/c* = 6 and 12 and c SDS 0.55-1.00 and 0.55-2.50 mass %, respectively, when a critical shear rate, γcrit, was exceeded, suggesting that a shear-induced structure formation in the mixtures occurred. © 2014 SCS. All rights reserved.