Zinc stearate

Zinc stearate

Names
IUPAC name zinc octadecanoate
Other names zinc distearate
Identifiers
CAS Number	557-05-1
3D model (Jmol)	Interactive image
ChemSpider	10705
ECHA InfoCard	100.008.321
PubChem	11178
UNII	H92E6QA4FV
InChI InChI=1S/2C18H36O2.Zn/c2*1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20;/h2*2-17H2,1H3,(H,19,20);/q;;+2/p-2 Key: XOOUIPVCVHRTMJ-UHFFFAOYSA-L InChI=1/2C18H36O2.Zn/c2*1-2-3-4-5-6-7-8-9-10-11-12-13-14-15-16-17-18(19)20;/h2*2-17H2,1H3,(H,19,20);/q;;+2/p-2 Key: XOOUIPVCVHRTMJ-NUQVWONBAX
SMILES [Zn+2].[O-]C(=O)CCCCCCCCCCCCCCCCC.[O-]C(=O)CCCCCCCCCCCCCCCCC
Properties
Chemical formula	C36H70O4Zn
Molar mass	632.33 g·mol^−1
Appearance	soft, white powder
Odor	slight, characteristic[1]
Density	1.095 g/cm^3, solid
Melting point	120 to 130 °C (248 to 266 °F; 393 to 403 K)
Boiling point	decomposes
Solubility in water	insoluble
Solubility in alcohol	insoluble
Solubility in ether	insoluble
Solubility in benzene	slightly soluble
Hazards
EU classification (DSD)	not listed
NFPA 704	2 1 0
Flash point	277 °C (531 °F; 550 K)
Autoignition temperature	420 °C (788 °F; 693 K)
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 15 mg/m^3 (total) TWA 5 mg/m^3 (resp)[1]
REL (Recommended)	TWA 10 mg/m^3 (total) TWA 5 mg/m^3 (resp)[1]
IDLH (Immediate danger)	N.D.[1]
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Zinc stearate is a "zinc soap" that is widely used industrially. In this context, soap is used in its formal sense, a metal "salt" of a fatty acid. It is a white solid that repels water. It is insoluble in polar solvents such as alcohol and ether but soluble in aromatic hydrocarbons (e.g., benzene) and chlorinated hydrocarbons when heated. It is the most powerful mold release agent among all metal soaps. It contains no electrolyte and has a hydrophobic effect. Its main application areas are the plastics and rubber industry, where it is used as a releasing agent and lubricant which can be easily incorporated.^[2]

Zinc carboxylates, e.g. basic zinc acetate, adopt complex formulas, and are not simply dicarboxylates of zinc. Instead the formula for most zinc carboxylates is Zn₄O(O₂CR)₆, consisting of a Zn₄O⁶⁺ core with carboxylate ligands spanning the edges.

Applications

It is widely used as a release agent for the production of many kinds of objects rubber, polyurethane, polyester processing system, powder metallurgy. These applications exploit its "non-stick" properties.^[2] In cosmetics, zinc stearate is a lubricant and thickening to improve texture.^[3]

It is an "activator" for rubber vulcanization by sulfur and accelerators. As discovered in the early days of vulcanization, zinc has a beneficial effect on the reaction of the sulfur with the polyolefin. The stearate is a form of zinc that is highly soluble in the nonpolar medium of the polyolefins.

Being lipophilic, it functions as a phase transfer catalyst for the saponification of fats.^[2]

Niche uses

It is a component of some paints, imparting gloss. As a chief ingredient in "fanning powder", it is used by magicians performing card manipulation to decrease the friction between the cards.

References

1. "NIOSH Pocket Guide to Chemical Hazards #0676". National Institute for Occupational Safety and Health (NIOSH).
2. David J. Anneken, Sabine Both, Ralf Christoph, Georg Fieg, Udo Steinberner, Alfred Westfechtel "Fatty Acids" in Ullmann's Encyclopedia of Industrial Chemistry 2006, Wiley-VCH, Weinheim. doi:10.1002/14356007.a10_245.pub2
3. http://cosmeticsinfo.org/ingredient/zinc-stearate