Temperature dependent rheology of surfactant-hydroxypropyl cellulose solutions. Page: 14
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viscosity increase can be attributed to the uncoiling of the polyelectrolyte, and the
resultant increased interaction between the polyelectrolyte molecules. The viscosity
decrease with increasing shear rate has been attributed to the reduction in the amount of
"three dimensional network structure" in the polyelectrolyte system.21
It has been a belief that surfactant adsorption can occur below the critical micelle
concentration, CMC, and is a cooperative process. This means that surfactant molecules
self-assemble on the polymer chain to form aggregates, which are smaller in size than
bulk micelles. As the aggregates accumulate on the polymer chain, the cloud point and
rheological properties begin to change. As more surfactant is added to the polymer
system, a point is reached where bulk micelles form.21
As the number of aggregates on the polymer chain increases, the polymer chains
may stretch out in response to the inter-aggregate electrostatic repulsion. The increases in
the adsorbed surfactant aggregates causes the effective volume occupied by the HPC
molecules in the solution to increase. The relative viscosity and relative shear parameter
results indicate that the bulk micelles break up the "three-dimensional polymer structure".
At high concentrations the relative shear parameters in the HTAB and HTAC systems are
less than that in the aqueous 1wt.% HPC solution.
HPMC Polymer Solutions
The interaction between hydroxypropylmethyl cellulose, HPMC, and SDS has
22 ji s D o c nrto
also been studied.22 Reduced specific viscosity was measured against SDS concentration
at specific HPMC concentrations. The HPMC concentrations were set at 0.05, 0.1, 0.2,
and 0.3% HPMC. For all four HPMC concentrations three distinct regions appeared in
the viscosity vs. SDS concentration curves. In region I, low SDS concentration (0 - 414
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Snively, C. Todd. Temperature dependent rheology of surfactant-hydroxypropyl cellulose solutions., thesis, December 2002; Denton, Texas. (https://digital.library.unt.edu/ark:/67531/metadc3312/m1/18/: accessed April 25, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; .