(411d) Controlling the Processing Behavior of Silica Agglomerates Using a Thermo-Responsive Binder

Dispersion of particle clusters is a very important step in industrial processing and is encountered in a wide range of industries. Dispersion occurs when the hydrodynamic forces that tend to pull particles apart overcome the cohesive forces that hold the cluster together. Binders are commonly used within particle clusters to alter cohesive forces.

The purpose of our work is to explore the feasibility of using a new class of binders based on chemical systems that respond to external stimuli. We hypothesize that changes in the cohesion of a particle cluster can be triggered by changing the processing variable to which the binder is responsive. In particular, we explore this assumption using agglomerates of silica powder bound with Poly(N-Isopropyl Acrylamide), PNIPAM, a thermo-responsive polymer. Changes in temperature are expected to lead to physical changes in the conformation of the PNIPAM chains thereby altering the cohesion of the agglomerate and the kinetics of its dispersion.

Experiments were conducted in a rotating cone-and-plate device. Silica agglomerates, suspended in a processing fluid, were subjected to a constant shear stress. The agglomerate size was monitored to evaluate dispersion. Tests were performed at room temperature and at 45°C using different shear stresses. Results show different dispersion levels for untreated and PNIPAM-modified silica agglomerates.