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Katja A. Fröhlich, Eleni Mitrentsis, Frank Clemens, Botho Hoffmann, Véronique Michaud, Thomas Graule
Assessment of the Dispersion Quality of refractive index-matched nanodispersions

Appl. Rheol. 26:6 (2016) 65050 (10 pages)

Dispersion quality has a large influence on the resulting properties of filled polymers, hybrids and nanocomposites in general. Reducing the van der Waals forces and therefore, matching the refractive index between the filler and the matrix should improve dispersion in hybrid materials. However, in this case the usual light-based techniques cannot be used to assess dispersion quality. In this work, dispersions containing silica nanoparticles and a solvent mixture of 1-butanol and benzyl alcohol were analysed by rheological methods. The refractive index of the solvent was changed by varying the mixing ratio, and thus the effect of index difference on the filler-matrix interaction was investigated. In agreement with theory, a stronger gel network was observed when the refractive index of filler and solvent were matched. If the difference in refractive index of the two materials became too large, particles and solvent interaction was reduced, and agglomerates were formed. This resulted in a weaker gel network.

Cite this publication as follows:
Frohlich KA, Mitrentsis E, Clemens F, Hoffmann B, Michaud V, Graule T: Assessment of the Dispersion Quality of refractive index-matched nanodispersions, Appl. Rheol. 26 (2016) 65050.

Vaidas Klimkevicius, Ricardas Makuska, Thomas Graule
Rheology of titania based ceramic nanodispersions stabilized by cationic comb copolymers

Appl. Rheol. 26:1 (2016) 15199 (9 pages)

Rheological studies of the ceramic based concentrated titania nanoparticle dispersions showed a clear correlation between molecular structure of the cationic polymers used as dispersants and the viscosity of the slurries. Dynamic viscosity of the electrostatically stabilized alkaline (pH 10.0) dispersions of the bare titania nanopowders with a solid loading of 15 - 25 wt.% was rather high (about 1 Pa.s) and the dispersions exhibited shear-thinning flow behavior. For electrostatic and steric stabilization of the concentrated ceramic nanodispersions of titania in alkaline conditions, the dispersions were treated with cationic comb copolymers differing in charge density and the length of PEO side chains. The dispersions treated by the cationic comb copolymers acted as the Newtonian fluids at low and medium shear rates (< 200 s-1) and showed shear-thickening flow behavior at higher shear rates. Dynamic viscosity of the dispersions with a solid loading of 15 - 25 wt.% treated by the cationic comb copolymers was very low (2 to 30 mPa.s). 1

Cite this publication as follows:
Klimkevicius V, Makuska R, Graule T: Rheology of titania based ceramic nanodispersions stabilized by cationic comb copolymers, Appl. Rheol. 26 (2016) 15199.


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