reagglomerointi

Reagglomerointi, or re-agglomeration, is the process by which dispersed particles in a suspension or powder re-cluster into larger aggregates after an initial dispersion or deagglomeration. It undermines dispersion quality by increasing effective particle size, which can raise viscosity, reduce stability, and alter flow or settling behavior. Reagglomeration can occur during handling, storage, drying, milling, or mixing when stabilizing interactions are overcome by attractive forces between particles.

The phenomenon arises from several mechanisms. Interparticle attractions such as van der Waals forces or electrostatic attraction can pull particles back together. Moisture or solvent remnants can create capillary bridges that bind particles, especially during drying or in humid environments. Surface interactions, differences in particle chemistry, or magnetic or cohesive forces can also promote re-clustering. The balance between stabilizing forces (electrostatic repulsion, steric hindrance, or surface modification) and attractive forces governs whether reagglomeration occurs.

Reagglomeration is a concern in many industries, including mineral processing, cement and ceramic production, pigment and coating formulations, catalyst supports, and pharmaceutical suspensions. It can lead to reduced surface area, altered rheology, poor packing, and degraded product performance, such as lower gloss in coatings or reduced dispersion stability in suspensions.

To prevent or control reagglomeration, formulations may employ dispersants or deflocculants to enhance repulsive interactions, surface-modifying coatings to provide steric stabilization, or adjustments in humidity and temperature to minimize capillary forces. Process strategies include optimized milling and mixing sequences, appropriate drying conditions, controlled solids loading, and keeping systems under agitation or using design features that minimize particle contact during storage. Measurements such as zeta potential, particle size distribution, and microscopy help assess dispersion stability and the extent of reagglomeration.