⁠Metallic Soaps

1. Calcium Stearate

Chemical Formula: Ca(C₁₇H₃₅COO)₂

Appearance: White, fine powder

Solubility: Insoluble in water; slightly soluble in hot oils

Functions:

• Acts as an external lubricant in PVC processing
• Serves as a co-stabilizer with other heat stabilizers
• Water-repellent agent in construction materials (e.g., cement, concrete)

Applications:

• Rigid PVC pipes and profiles
• Pharmaceutical tablets (anti-adherent)
• Powder coatings and masterbatches
• Food packaging (FDA-approved grade available)

Advantages:

• Non-toxic
• Good thermal stability
• Low cost

2. Zinc Stearate

Chemical Formula: Zn(C₁₇H₃₅COO)₂

Appearance: Fine, white hydrophobic powder

Solubility: Insoluble in water; dispersible in oils

Functions:

• High-performance mold release agent
• Used as a co-stabilizer with calcium stearate in Ca/Zn systems
• Enhances gloss and surface finish in plastics

Applications:

• Injection molded PVC and polyolefins
• Rubber compounds and EVA
• Masterbatches and one-pack stabilizers
• Paints, varnishes, cosmetics

Advantages:

• Non-toxic
• Effective at low dosages
• Anti-tack and anti-caking agent in powders

3. Magnesium Stearate

Chemical Formula: Mg(C₁₇H₃₅COO)₂

Appearance: Very fine, white powder

Solubility: Insoluble in water

Functions:

• Lubricant and flow agent in tablet and capsule manufacturing
• Acts as anti-adherent to prevent sticking
• Occasionally used as internal lubricant in plastics

Applications:

• Pharmaceutical excipients (widely used)
• Food supplements (nutraceuticals)
• Thermoplastics (limited use)

Advantages:

• FDA/USP compliant
• Inert and safe for human consumption

4. Aluminum Stearate

Chemical Formula: Al(C₁₇H₃₅COO)₃

Appearance: White, waxy powder

Solubility: Insoluble in water; soluble in hot oils and organic solvents

Functions:

• Gelling and thickening agent
• Provides water repellency
• Improves pigment dispersion in paints and inks

Applications:

• Paints and coatings
• Lubricating greases
• Polyolefin masterbatches
• Cosmetic formulations (e.g., creams)

Advantages:

• Excellent thickening properties
• Stable in a wide pH range

5. Barium Stearate

Chemical Formula: Ba(C₁₇H₃₅COO)₂

Appearance: White powder

Solubility: Insoluble in water

Functions:

• Acts as a heat stabilizer in PVC (often with cadmium or zinc stearate)
• Used as a processing aid in plastics

Applications:

• Flexible and rigid PVC (historical use)
• Wire & cable insulation
• Plasticized film production

Limitations:

• Low toxicity compared to lead, but declining use due to regulatory pressures