IOTA corporation ltd
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In the preparation of water-in-oil (W/O) emulsions, formulators often face a tricky problem: when the water phase proportion is low and a large amount of polyols such as glycerol and propylene glycol are added, salts like sodium chloride and magnesium sulfate that were originally easily soluble become difficult to dissolve, seriously affecting production efficiency and product stability. Recently, industry experts have uncovered this mystery from the molecular mechanism level and proposed targeted solutions, providing important references for formulation optimization in the cosmetics and related industries.
From a microscopic perspective, water molecules dissociate salt lattices through ion-dipole interactions and high dielectric shielding effects to achieve salt dissolution. The addition of polyols hinders this process in three ways: first, it sharply increases the viscosity of the water phase through strong hydrogen bonding, reducing ion diffusion rate and forming a saturated concentrated liquid layer on the crystal surface; second, it competes for water molecules to form a hydration network, reducing the number of effective water molecules available for dissolution; third, its dielectric constant is much lower than that of water, weakening the ability to reduce ion attraction. Data shows that at 25℃, the dielectric constant of glycerol is 42.5 and that of propylene glycol is only 32, far lower than 80 of water.
In response to this physicochemical limitation, experts have put forward practical optimization schemes: first, adjust the feeding sequence to completely dissolve the salt in pure water before adding polyols; second, raise the water phase temperature to 60-70℃ to offset the diffusion resistance caused by high viscosity; at the same time, use high-shear stirring during the water phase preparation stage to break the high-concentration diffusion layer on the crystal surface. In addition, different salts have different solubilities—monovalent salts such as sodium chloride are usually more soluble than divalent salts such as magnesium sulfate, which can be reasonably selected in formulation design.
This research result not only solves the long-standing technical puzzle in the industry but also helps enterprises improve production efficiency and ensure product quality through clear process adjustment suggestions, providing theoretical support and practical guidance for cosmetic formulation innovation.
