In the field of cosmetic R&D, Zeta potential, as a key parameter characterizing colloid stability, is rarely directly used in daily formulation operations, but plays an irreplaceable role in solving product stability problems. From the uniform dispersion of sunscreen lotions to the viscosity control of personal care products, this physical parameter runs through the core link of cosmetic formulation design. Zeta potential refers to the potential difference between the ion layer adsorbed on the surface of colloidal particles and the dispersion medium, and its value directly determines the particle aggregation behavior. Taking physical sunscreens such as nano-titanium dioxide and zinc oxide as examples, such nano-particles are prone to aggregation due to their high specific surface area and surface free energy. When the absolute value of Zeta potential is higher than 30mV, the strong electrostatic repulsion between particles can effectively offset the van der Waals attraction, ensuring the uniform dispersion of sunscreen ingredients and extending the product's sun protection effect; if the absolute value is lower than 20mV, problems such as stratification and caking are likely to occur, seriously affecting the user experience.
    In personal care products, Zeta potential is the core code for viscosity control. Micelles formed by anionic surfactants generate Zeta potential through the electric double layer structure. When the absolute value is high, the micelles are dispersed independently, and the system viscosity is low; after adding electrolytes such as sodium chloride, the absolute value of the micelle Zeta potential decreases, the electrostatic repulsion weakens, and the micelles aggregate to form a network structure, which can significantly increase the product consistency. It is worth noting that although electrolytes in water-in-oil products will reduce the Zeta potential, the stability can be compensated by mechanisms such as lowering the freezing point of the aqueous phase and strengthening the interface film.
    Zeta potential is affected by multiple factors such as pH value, particle characteristics, and electrolyte concentration. The pH value changes the charging property of the particle surface groups, and there is an isoelectric point where the potential is zero; the higher the electrolyte concentration and the higher the valence of the counterion, the more obvious the decrease in the absolute value of the potential; ionic surfactants directly change the particle charge, while non-ionic surfactants indirectly affect the electric double layer structure through the adsorption layer. At present, the laser electrophoresis method has become the mainstream measurement method due to its accuracy and convenience, while the streaming potential method and ultrasonic electrophoresis method are suitable for special systems.
    As a key parameter for predicting the shelf life of cosmetics, the in-depth research on Zeta potential provides a scientific basis for formulation innovation, helping the industry create more stable and efficient beauty products.

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