Polyhydroxystearic Acid (PHS) CAS 27924-99-8

Polyhydroxystearic Acid – Polymeric Emulsifier and Dispersant for Cosmetics and Sunscreens

Chemical Structure and Synthesis
Polyhydroxystearic acid is a polymer composed of repeating hydroxystearic acid units, typically obtained by the polycondensation of 12‑hydroxystearic acid (derived from castor oil). The general structure can be represented as:
[–OC(O)–C₁₇H₃₅–CHOH–]ₙ
By controlling reaction conditions (catalyst, temperature, stoichiometry), the degree of polymerization and thus the molecular weight and physicochemical properties can be tailored to meet specific formulation requirements.

Physicochemical Properties

• Emulsifying and dispersing activity: Effectively stabilizes oil‑in‑water (O/W) and water‑in‑oil (W/O) emulsions, reduces interfacial tension, and improves emulsion stability over time.

• Excellent pigment dispersion: Enhances dispersion of pigments and UV filters in color cosmetics, sunscreens, and foundations, improving color intensity and uniformity.

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

• 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.

• Thermal stability: Maintains properties across a range of temperatures.

Applications

• Sunscreens: Used as a dispersant for inorganic UV filters (zinc oxide, titanium dioxide) and as an emulsion stabilizer.

• Color cosmetics: Foundations, lipsticks, eyeliners, and mascaras – improves pigment dispersion, provides uniform color, and enhances wear.

• Skin care: Creams, lotions, and serums – stabilizes emulsions, improves spreadability, and reduces greasiness.

• Other: Can be used as a co‑emulsifier and stabilizer in various cosmetic and pharmaceutical formulations.

Key Benefits

• Effective emulsification and stabilization of oil‑water systems.

• Excellent pigment and UV filter 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 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.