Stearamidopropyl Dimethylamine

Stearamidopropyl Dimethylamine – Cationic Surfactant and Emulsifier for Hair and Skin Care

Chemical Structure and Synthesis
Stearamidopropyl dimethylamine is a tertiary amine surfactant synthesized by the amidation of stearic acid (C18 saturated fatty acid) with 3-aminopropyldimethylamine. Its molecular structure can be represented as:
CH₃(CH₂)₁₆CO–NH–(CH₂)₃–N(CH₃)₂

The synthesis involves the reaction:
Stearic Acid + 3-Aminopropyldimethylamine → Stearamidopropyl Dimethylamine + H₂O
The long saturated C18 chain provides strong lipophilic character, while the tertiary amine group offers hydrophilicity and cationic activity upon protonation.

Physicochemical Properties

• High lipophilicity – excellent compatibility with oils and waxes.

• Conditioning effect – imparts softness, improves wet and dry combability, and reduces static charge on hair.

• Emulsifying activity – stabilizes oil-in-water (O/W) and water-in-oil (W/O) emulsions.

• Antistatic properties – reduces flyaway and frizz.

• pH-responsive – can be protonated to form a cationic salt, enhancing water dispersibility and substantivity to hair and skin.

• Mild and skin-friendly – low irritation potential.

Applications

• Hair care: Conditioners, shampoos, leave-in treatments, hair masks – improves softness, shine, and manageability.

• Skin care: Creams, lotions, moisturizers – provides emollient and smoothing effects.

• Cleansing products: Body washes, facial cleansers – enhances foam texture and skin feel.

• Emulsions: Stabilizes O/W and W/O systems, improving product consistency and stability.

• Other: Used in fabric softeners and industrial formulations.

Key Benefits

• Provides superior conditioning and antistatic properties.

• Enhances softness and manageability of hair.

• Stabilizes emulsions and improves product texture.

• Compatible with cationic, non-ionic, and amphoteric surfactants.

• Mild and low irritation – suitable for sensitive skin.

• Plant-derived stearic acid base – renewable and biodegradable.

• Acts as a co-emulsifier and thickener in complex formulations.

Recommended Use
Typical usage levels range from 0.5–3% in rinse-off products and 1–5% in leave-on formulations, depending on the desired conditioning effect and emulsion stability. For optimal performance, incorporate into the oil phase with mild heating (60–70°C). Can be neutralized with acids (e.g., citric acid, lactic acid) to form cationic salts, enhancing water dispersibility and conditioning efficacy.

Safety and Handling

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

• Low irritation potential; well-tolerated by skin and eyes.

• 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 amine value, purity, and conditioning performance to ensure consistent quality.