Chemistry:Zinc borate
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
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Zinc borate refers to a family of inorganic compounds consisting of borate of zinc. They are white solids with the formulas:
- ZnO · B
2O
3 · 1.12H2O - ZnO · B
2O
3 · ~ 2H
2O - ZnO · 5B
2O
3 · 4.5H2O - 2ZnO · 3B
2O
3 · 3H2O - 2ZnO · 3B
2O
3 · 7H2O - 3ZnO · 5B
2O
3 · 14H2O - 4ZnO · B
2O
3 · H2O - 6ZnO · 5B
2O
3 · 3H2O
They are coordination polymers consisting of zinc(II) centers bonded to cyclic boron oxide rings.[1]
Variants
Several variants of zinc borate exist, differing by the zinc/boron ratio and the water content:[2]
- Zinc borate Firebrake ZB (2ZnO · 3B
2O
3 · 3.5H2O), CAS number 138265-88-0 - Zinc borate Firebrake 500 (2ZnO
3 · 3B
2O
3), CAS number 12767-90-7 - Zinc borate Firebrake 415 (4ZnO · B
2O
3 · H2O), CAS number 149749-62-2 - ZB-467 (4ZnO · 6B
2O
3 · 7H2O), CAS number 1332-07-6 - ZB-223 (2ZnO · 2B
2O
3 · 3H2O), CAS number 1332-07-6
The hydrated variants lose water between 290–415 °C (554–779 °F).
Uses
Zinc borate is primarily used as a flame retardant in plastics and cellulose fibers, paper, rubbers and textiles. It is also used in paints, adhesives, and pigments. As a flame retardant, it can replace antimony(III) oxide as a synergist in both halogen-based and halogen-free systems.[3] It is an anti-dripping and char-promoting agent, and suppresses the afterglow. In electrical insulator plastics it suppresses arcing and tracking.
In halogen-containing systems, zinc borate is used together with antimony trioxide and alumina trihydrate. It catalyzes formation of char and creates a protective layer of glass. Zinc catalyzes the release of halogens by forming zinc halides and zinc oxyhalides.
In halogen-free system, zinc borate can be used together with alumina trihydrate, magnesium hydroxide, red phosphorus, or ammonium polyphosphate. During burning the plastics, a porous borate ceramics is formed that protects the underlying layers. In presence of silica, borosilicate glass can be formed at plastic burning temperatures.[4]
Zinc borate is used in polyvinyl chloride, polyolefins, polyamides, epoxy resins, polyesters, thermoplastic elastomers, rubbers, etc. It is also used in some intumescent systems.[5]
Zinc borate has synergistic effect with zinc phosphate or barium borate as a corrosion inhibitor pigment.
Zinc borate acts as a broad-spectrum fungicide in plastics and wood products.[6]
Zinc borate can be used as a flux in some ceramics. In electrical insulators it improves the ceramics properties.
References
- ↑ 1.0 1.1 Schubert, David M.; Alam, Fazlul; Visi, Mandana Z.; Knobler, Carolyn B. (2003). "Structural Characterization and Chemistry of the Industrially Important Zinc Borate, Zn[B3O4(OH)3]". Chemistry of Materials 15 (4): 866–871. doi:10.1021/cm020791z.
- ↑ "Flame Retardants Fact Sheet, Zinc borate". Cefic. January 2006. http://www.cefic-efra.com/Objects/2/Files/ZincBorateFactsheet.pdf.
- ↑ "Zinc Borate (Boric Acid, Zinc Salt)". Chemical Land21. http://chemicalland21.com/industrialchem/inorganic/ZINC%20BORATE.htm.
- ↑ "Firebrake zinc borates for plastics". Luzenac Group. http://www.luzenac.com/plastics_zinc_borate.htm.
- ↑ Bellingham, F. (25 November 1992). "Zinc borate in intumescent paints". European Polymers Paint Colour Journal. http://www.accessmylibrary.com/article-1G1-13603942/zinc-borate-intumescent-paints.html. Retrieved 6 February 2010.
- ↑ "zinc borate (Firebreak ZB) EPA Pesticide Fact Sheet 10/91". Pesticide Management Education Program. 1 October 1991. https://pmep.cce.cornell.edu/profiles/fung-nemat/tcmtb-ziram/zinc-borate/fung-prof-zinc-borate.html.
External links
- Zinc borate in the Pesticide Properties DataBase (PPDB)
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