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Colloidal Processing of Silicon Nitride with Poly(acrylic acid): II, Rheological Properties
Author(s) -
Hackley Vincent A.
Publication year - 1998
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1998.tb02638.x
Subject(s) - polyelectrolyte , dispersant , materials science , polymer , chemical engineering , rheology , colloid , acrylic acid , shear thinning , polymer chemistry , flocculation , particle (ecology) , aqueous solution , silicon nitride , composite material , chemistry , organic chemistry , monomer , physics , oceanography , geology , optics , engineering , dispersion (optics) , layer (electronics)
Poly(acrylic acid) (PAA) was the focus of an investigation in the role and behavior of polyelectrolyte dispersants in aqueous‐based colloidal processing of silicon nitride. The steady‐shear flow properties of dense suspensions were examined as a function of pH, particle volume fraction, chain length, and polymer concentration. Suspensions exhibited shear‐thinning behavior, which was analyzed using the constitutive Bingham equation for plastic flow. The data showed that polyelectrolyte charge and configuration were important in the observed flow behavior. In acidic media, PAA behaved similar to a neutral polymer in a poor solvent, whereas, in alkaline media, PAA behaved similar to a rigid asymmetric particle. Although electrostatic forces dominated flow properties in alkaline media, where PAA was predominantly in the free‐polymer form, at lower pH values, PAA interactions with the particle surface resulted in a complex array of suspension effects, including polymer bridging, electrosteric stabilization, and flocculation.