Three steps to a perfect dispersion

摘要

When is particle not a particle? When it's an aggregate or an agglomerate. Zinc oxide in a typical sunscreen product exists not as individual crystals-the primary particles-but particle aggregates: groups of two or more primary particles that have bonded irreversibly together during the manufacturing process. Primary particles never make up more than a tiny fraction of the zinc oxide present, whereas aggregates predominate in a well-prepared dispersion.