Polyhydroxystearic Acid (PHS)

Polyhydroxystearic Acid (PHS) – Polymeric Emulsifier and Structuring Agent for Cosmetics and Technical Applications

Chemical Structure and Synthesis
Polyhydroxystearic acid is a polymer composed of hydroxystearic acid units, typically obtained by the polycondensation of 12-hydroxystearic acid (derived from castor oil or hydrogenation of ricinoleic acid). The synthesis can be represented as:
n HO–C₁₇H₃₅COOH → Polyhydroxystearic Acid + (n−1) H₂O
By controlling reaction conditions (catalyst, temperature, stoichiometry), the degree of polymerization and thus the molecular weight and physicochemical properties of the product can be tailored to meet specific formulation requirements.

Physicochemical Properties

• Emulsifying activity: Multiple hydroxyl groups along the polymer chain enable active interaction with both aqueous and oil phases, promoting emulsion stabilization and reducing interfacial tension.

• Structuring ability: Enhances the texture and consistency of final products, contributing to the formation of homogeneous, stable systems.

• Dispersing properties: Effectively disperses pigments and particles in color cosmetics, foundations, and sunscreens, improving color intensity and uniformity.

• Skin feel: Imparts a soft, velvety feel and reduces the greasiness of oil-based products.

• Thermal stability: The polymeric structure maintains properties across a range of temperatures.

• Good oil compatibility: Soluble in oils and lipophilic systems, making it suitable for anhydrous and emulsion formulations.

• Plant-derived and biodegradable: Derived from renewable castor oil sources, environmentally friendly.

Applications

• Cosmetics and personal care: Used as an emulsifier, dispersant, and stabilizer in sunscreens, lotions, creams, foundations, and color cosmetics. Improves spreadability, reduces greasiness, and imparts a soft, velvety feel.

• Lubricants and greases: Acts as a structuring and thickening agent, improving consistency and stability of lubricating compositions.

• Industrial and technical formulations: Employed as a dispersant and emulsion stabilizer in various polymer systems and specialty chemical products.

Key Benefits

• Effective emulsification and stabilization of oil-water systems.

• Excellent pigment and particle dispersion – enhances color intensity and uniformity.

• Improves texture and imparts a pleasant, non-greasy skin feel.

• Thermal and oxidative stability – reliable over a wide temperature range.

• Plant-derived and biodegradable – environmentally friendly.

• Compatible with a wide range of cosmetic and industrial ingredients.

• Acts as a thickener, structurant, and stabilizer in complex formulations.

Recommended Use
Typical usage levels range from 1–5% of the formulation, depending on the desired emulsion stability, viscosity, and dispersing effect. For optimal performance, dissolve in the oil phase at elevated temperatures (60–80°C) before emulsification. Can be combined with co-emulsifiers and thickeners for tailored rheology.

Safety and Handling

• Generally recognized as safe for use in cosmetics and personal care at recommended concentrations.

• Low irritation potential; well-tolerated by skin.

• Avoid contact with strong oxidizers and acids.

• Store in a cool, dry place, away from direct sunlight.

• Use appropriate personal protective equipment (gloves, safety goggles) when handling.

Quality Assurance
Each batch is tested for acid value, hydroxyl value, and emulsification performance to ensure consistent quality.