Dispersancy

Dispersancy is the property of a material to disperse as discrete particles within a liquid medium and to remain dispersed rather than aggregating or settling. In colloid and materials science, dispersancy is closely related to dispersion stability, a critical factor in the performance of paints, inks, coatings, ceramics, pharmaceuticals, and mineral slurries. A system with high dispersancy forms a uniform suspension that resists sedimentation and phase separation over time; low dispersancy leads to sedimentation, flocculation, or haze.

Several factors influence dispersancy. Particle size and shape affect how readily particles can separate and spread. Surface characteristics, including charge and the presence of adsorbed molecules, determine interparticle repulsion or attraction. The medium’s properties—polarity, pH, ionic strength, and temperature—alter electrostatic and solvation interactions. Steric stabilization from polymeric or surfactant layers can provide barriers to close approach, enhancing dispersancy.

Measurement and assessment of dispersancy commonly involve particle-size analysis, zeta potential to gauge surface charge, sedimentation or centrifugation tests, rheological measurements, and turbidity or microscopic observation. Together, these methods indicate how well a system resists aggregation and maintains a stable dispersion.

Practically, dispersancy is improved by adding dispersants or surface-modifying agents that adsorb onto particle surfaces, promoting electrostatic or steric stabilization. In industrial contexts, higher dispersancy in paints and inks yields better color strength and flow, while in lubricants, ceramics, and cementitious systems, it supports uniform particle distribution, lower viscosity, and reduced tendency toward sludge or settling.