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 octylphen ol adduct containing an average of 10 oxyethylene units (C8H17C6H4O(EO)(10) H). Three associative polymer families are examined: Hydrophobically-modifi ed, alkali-swellable emulsion (HASE); hydrophobically-modified hydroxyethyl cellulose (HMHEC); and hydrophobically-modified, ethoxylated urethanes (HE UR). At a critical concentration, the: addition of SDS to HASE or HMHEC sol utions increases their viscosities; however, the addition of the nonionic s urfactant, C8H17C6H4O(EO)(10)H, has only a minimal influence in enhancing s olution viscosities. In the presence of these two surfactants, a series of HEUR thickeners, synthesized by a step-growth (S-G) process, exhibited a si gnificant deviation from HMHEC and HASE solutions. As the effective termina l hydrophobe size of the S-G HEURs is increased, the viscosities of the non ionic 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 obs erved in SDS solutions with increasing sodium chloride concentrations also are discussed. (C) 1999 Elsevier Science B.V. All rights reserved.