Zinc borate, CAS number 1332-07-6, molecular formula 2ZnO.3B2O3.3.5H2O, is characterized by small particle size, uniform distribution, insolubility in water, low specific gravity, and good shell-forming properties. It exhibits good flame-retardant effects in coatings, paints, resins, rubber, plastics, cables, and synthetic fibers, and can partially replace antimony trioxide (Sb2O3). It also provides bactericidal and insect-repellent effects.

I. Basic Information

English Name: Zinc borate; ZB

CAS NO: 1332-07-6

Molecular Formula: 2ZnO.3B2O3.3.5H2O

Molecular Weight: 125.2261

ECN NO: 215-566-6

Specific Gravity: 2.36

Refractive Index: 1.580-1.599

Appearance: White powder

II. Mechanism of Flame Retardant and Antibacterial Action

1. At temperatures above 300℃, zinc borate dehydrates, absorbing a large amount of heat from the surrounding material, lowering the temperature of the material environment, and also foaming, diluting combustible gases.

2. ZB has a certain char-forming effect, forming an inorganic expansion coating layer on the material surface, isolating combustible gas exchange and preventing heat transfer.

3. It inhibits and interrupts the continuous reaction of combustible free radicals.

4. At high temperatures, zinc borate decomposes to generate B₂O₃ (and ZnX₂ and ZnOX if the material contains chlorine or bromine, where X is Cl or Br), forming a coating layer on the polymer surface. This coating layer inhibits the generation of flammable gases and prevents oxidation and thermal decomposition. Furthermore, in halogen-containing materials, BX₃ is produced during combustion. BX₃ reacts with water in the gas phase to generate HX, producing halogen free radicals in the flame. These free radicals can inhibit the chain reaction of hydroxyl free radicals, thus providing flame retardancy.

5. Zinc borate (ZB) is toxic to cells and acts as an enzyme inhibitor. By inhibiting enzyme activity in the cell, it suppresses fungal growth and has a wide range of effects on organisms that damage wood fibers, such as white-rot and brown-rot fungi, as well as termites and other insects that damage wood-based panels.

III. Product Specifications

Content ≥99%

Whiteness ≥95%

Moisture % ≤0.5%

Particle Size (D50): 3-5μm

Zinc Oxide: 36.5-39.5%

Borne Oxide: 46.0-49.0%

Loss on Ignition: 13.0-15.5%

Residue on 325 Mesh Sieve ≤ 0.5%

Heavy Metal Pb≤15ppm

Specific Gravity: 2.67g/cm³

Melting Point: 980℃

Refractive Index: 1.58

IV. Product Features

1. Good dispersibility and thermal stability; insoluble in water; can partially replace antimony trioxide (Sb₂O₃).

2. Can be compounded with various other halogenated or halogen-free flame retardants for synergistic flame retardancy.

3. Zinc borate has excellent resistance to precipitation; odorless, non-toxic, and non-corrosive.

4. It possesses halogen-free flame retardant, synergistic flame retardant, smoke suppression, and smoke elimination effects.

5. It is resistant to high temperatures and suitable for high-temperature processing.

6. It has good flame retardant effect on polymer charring.

V. Applications

1. EVA mixed with ZB and Al(OH)3 or MgCO₃ for flame retardancy can be used as a halogen-free cable sheathing layer, producing cables with very low optical signal transmission loss. Mixtures with Al(OH)3 can also be used to retard acrylic emulsions, ethylene acrylate copolymers, and EPDM rubber; the flame-retardant materials are also used for wire and cable sheathing.

2. Zinc borate flame retardants are also effective; in rigid PVC, they can achieve good flame retardant properties when used alone. In various polymers such as flexible PVC, PP, and rubber, it is mainly used as a synergist in combination with inorganic flame retardants such as antimony trioxide, aluminum hydroxide, and magnesium hydroxide, or organic flame retardants such as bromine-based flame retardants. It has excellent smoke suppression and charring promotion effects, and plays a role in adjusting the flame retardant, physical, and electrical properties of the product. Main applications include wires and cables, engineering plastics, bakelite, conveyor belts, rubber tires, and artificial leather. The commonly used addition amount is 1-10%.

3. In the chemical, steel, and coal industries, it is mainly used to manufacture various flame-retardant tapes (pipes) and flame-retardant cables. It can replace antimony trioxide, has good flame retardancy for halogenated polymers, can completely replace antimony trioxide in unsaturated polyesters, and can partially replace antimony trioxide in flexible PVC resin. It is suitable for high-temperature processing. It also has a good synergistic effect when used in combination with halogenated flame retardants. It is suitable for flame retardant applications in unsaturated polyesters, PVC, epoxy resins, polyolefins, polycarbonates, polyurethanes, ABS resins, and other plastics. It is also suitable as a flame retardant additive for fiber fabrics and wood coatings. Furthermore, zinc borate is an effective flame retardant; in systems such as unsaturated polyester, rigid PVC, epoxy compounds, and polyphenylene ether, zinc borate alone can achieve a flame retardant effect. In other systems, such as flexible PVC products, the flame retardant effect of zinc borate is poor; to obtain better results, it is used in combination with antimony trioxide.

4. It can be used as a corrosion inhibitor in coatings. ZB can be used as a rust inhibitor in coatings using organic or water-based solvents. 2ZnO.3B2O3.3.5H2O offers better cost-effectiveness than adding chromium, lead, or barium pigments. In coating formulations, ZB provides better performance by weight substitution for zinc chromate. When used in combination with zinc phosphate, barium metaphosphate, and other corrosion inhibitors, it has a good synergistic effect. The water of crystallization in zinc borate only begins to decompose and release at 300 ℃, so it can be used in some high-temperature baking systems. The general addition ratio is 0.03-0.3 g/ml.

5. It has good antibacterial effects on wood and plastic materials. Zinc borate (ZB) can be used as an antibacterial agent to protect wood or wood-plastic composites from decay. It is added to the raw materials during the mixing stage and can be evenly distributed throughout the wood-plastic system. It can inhibit the growth of decay fungi, such as white rot fungi and *Cladosporium glomeratum, and also prevent insect infestation. The resistance of wood-plastic products to fungi depends on the type of wood, the type of resin, other additives used, and the processing method. The applicable proportion of zinc borate should not exceed 8%. When the content exceeds 1.5%, the amount of binder needs to be appropriately increased to increase strength.

6. It can be used in agricultural fertilizers, micronutrient fertilizers, hydroponics nutrient solution additives, ceramic glazes, and also in medicine as a bactericide, mildew inhibitor, preservative, and rust-preventing pigment. It is also used in far-infrared absorption and insect and fungal treatment of wood.

VI. Storage Conditions

Store in a cool, dry, and well-ventilated warehouse. Shelf life is 12 months.

VII. Packaging Specifications

25KG packaging bags, 500KG packaging bags, 1000KG packaging bags, etc.

Zinc borate partially replaces antimony trioxide (Sb₂O₃), significantly improving flame retardant effects and reducing smoke production. Adding ZB to bromine-antimony flame retardants or masterbatches can also reduce the amount of halogenated flame retardants used. It exhibits good flame retardant effects on materials such as PP, PE, PVC, PA, PS, EP, PBT, PET, natural rubber, neoprene rubber, and nitrile rubber. It also has rust-preventing, bactericidal, mildew-preventing, and corrosion-preventing properties.