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Hydrophobically modified urethane-ethoxylate (HEUR) associative thickeners. 1. Rheology of aqueous solutions and interactions with surfactants
YKI – Ytkemiska institutet.
1994 (English)In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, ISSN 0927-7757, E-ISSN 1873-4359, Vol. 82, 263-277 p.Article in journal (Refereed)
Abstract [en]

The rheological properties of aqueous solutions of hydrophobically modified ethylene oxide urethane block copolymers, or HEUR thickeners, of different chemical compositions have been studied. A steep increase in viscosity with increasing thickener concentration is obtained at a concentration that increases with decreasing polymer molecular weight as predicted by a simple network model. However, this model does not predict the efficiency of the thickener, that is greatly effected by the hydrophobicity of the terminal hydrocarbon chains, and decreases in the order octadecyl > pentadecyl > 9-heptadecenyl. The more hydrophobic the end groups, the stronger are the crosslink points in the network, and as a consequence the more elastic is the solution. In HEUR solutions adjusted to the low shear viscosity 10 Pa s, 6-12 % of the thickener molecules are elastically effective in the network and the upper limit of the aggregation number is 40-60. The addition of surfactant increases the viscosity of the HEUR solutions, until, for most systems, a maximum is reached after which the viscosity decreases. The magnitude of the variation in viscosity is dependent on the chemical structures of both the polymer and the surfactant. The observed differences can be explained qualitatively by stoichiometric considerations of the mixed aggregates that are assumed to be formed between the hydrophobic chains of the polymer and the surfactant. Additional informa-tion relating to the HEUR-surfactant interaction was obtained from surface tension measurements. A nonionic surfactant is bound by a noncooperative process only to the hydrophobic aggregates of the HEUR. Sodium dodecyl sulphate is bound both to the hydrophobic domains and to the ethylene oxide blocks of the HEUR polymers.

Place, publisher, year, edition, pages
1994. Vol. 82, 263-277 p.
Keyword [en]
Associative thickener, network, rheology, surface tension, surfactant
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:ri:diva-26469OAI: oai:DiVA.org:ri-26469DiVA: diva2:1053471
Note
A846Available from: 2016-12-08 Created: 2016-12-08Bibliographically approved

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