Zinc stearate

Zinc stearate
IUPAC name zinc octadecanoate
Other names zinc distearate
Identifiers
CAS number	557-05-1 Y
PubChem	11178
ChemSpider	10705 Y
UNII	H92E6QA4FV Y
Jmol-3D images	{{#if:[Zn+2].[O-]C(=O)CCCCCCCCCCCCCCCCC.[O-]C(=O)CCCCCCCCCCCCCCCCC|Image 1
SMILES [Zn+2].[O-]C(=O)CCCCCCCCCCCCCCCCC.[O-]C(=O)CCCCCCCCCCCCCCCCC
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 Y Key: XOOUIPVCVHRTMJ-UHFFFAOYSA-L Y 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
Properties
Molecular formula	C36H70O4Zn
Molar mass	632.35 g mol−1
Appearance	soft, white powder
Density	1.095 g/cm³, solid
Melting point	120–130 °C
Boiling point	decomposes
Solubility in water	insoluble
Solubility in benzene	slightly soluble
Hazards
EU classification	not listed
NFPA 704	2 1 0
Flash point	277 °C; 531 °F; 550 K
Autoignition temperature	420 °C; 788 °F; 693 K
Y (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
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.^[1]

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.^[1] In cosmetics, zinc stearate is a lubricant and thickening to improve texture.^[2]

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.^[1]

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