Surfactant and salinity influences on associative thickener aqueous solution rheology

The rheological behavior of a series of associative polymers are studied in aqueous solutions containing sodium dodecyl sulfate (SDS) and an octylphenol adduct containing an average of 10 oxyethylene units (C8H17C6H4O(EO)(10)H). Three associative polymer families are examined: Hydrophobically-modified, alkali-swellable emulsion (HASE); hydrophobically-modified hydroxyethyl cellulose (HMHEC); and hydrophobically-modified, ethoxylated urethanes (HEUR). At a critical concentration, the: addition of SDS to HASE or HMHEC solutions increases their viscosities; however, the addition of the nonionic surfactant, C8H17C6H4O(EO)(10)H, has only a minimal influence in enhancing solution viscosities. In the presence of these two surfactants, a series of HEUR thickeners, synthesized by a step-growth (S-G) process, exhibited a significant deviation from HMHEC and HASE solutions. As the effective terminal hydrophobe size of the S-G HEURs is increased, the viscosities of the nonionic surfactant solutions become more viscous than the anionic solutions.:These transitions are accompanied by other rheological behaviors associated with increasing elastic character. Differences in rheological behavior observed in SDS solutions with increasing sodium chloride concentrations also are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.