Zinc stearate

Zinc stearate (CAS 557-05-1), also known as zinc distearate and approved as E366, is a metal soap produced from stearic acid and zinc.

Where is Zinc stearate used?

• Rubber and plastics: prevents adhesion to molds and processing equipment
• Extrusion and calendering: improves compound flow
• PVC: heat stabilizer and internal lubricant reducing degradation at high temperature
• Cosmetics and personal care: binder and slip agent in pressed powders, foundations and talc-based formulations
• Construction and paper: hydrophobic surface treatment and anti-blocking agent
• Coatings, board production and concrete release compounds: applied as release and anti-blocking aids
• It functions primarily as a release agent, lubricant and stabilizer in manufacturing processes.
• Used as a polishing agent in textile products to increase surface hydrophobicity.
• Used as a catalyst in chemical syntheses.
• Used as a matting additive in lacquers.

Good to know: Food-additive grade is available under the E366 designation, often meeting FCC or USP quality standards; Ph. Eur., BP or EP requirements may apply. Not to be confused with other metal soaps.

Formulation notes

• Has one of the lowest melting points (120 °C) compared to other metal soaps, allowing it to be distributed homogeneously during thermal incorporation.
• When mixed with strong mineral acids, it decomposes into stearic acid and corresponding zinc sulfates.

Typical specification

• Free fatty acid content of maximum 1.5%.
• Typically contains between 13.5% and 15% zinc oxide.
• Available in various product forms, including powders and low-dust forms, each in animal and vegetable variants.
• Fine particle structure with a maximum residue of 0.10% on a 200 mesh sieve.
• Sieve analysis residue on a 200 mesh sieve is maximum 0.10% according to ASTM D-1514.

Regulatory status

• Not classified as hazardous under CLP.

Storage, packaging and handling

• Should be stored away from open flames and sources of ignition.
• Prevent dust deposition when handling.

Frequently asked questions about Zinc stearate

What product forms are available for different polymer applications?

Low-dust spray granulate and flake forms are used for polyethylene and rubber, while a low-dust pastille form is used for polyethylene and polystyrene.

What is the difference between technical and laboratory grades?

Technical and laboratory grades are available, with the latter intended for laboratory use.

Technical content is compiled and updated by the SoleChem product team from public technical sources; the certificate of analysis (COA) governs product-specific specifications.