Sodium Antimonate as Fiber Flame Retardants

Application of sodium antimonate as a substitute for antimony trioxide in fiber flame retardants: technical principles and advantages and disadvantages analysis

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Introduction

As global requirements for the environmental friendliness and safety of flame-retardant materials increase, the fiber and textile industry urgently needs to explore alternatives to traditional flame retardants. Antimony trioxide (Sb₂O₃), as the core synergist of halogen flame retardant systems, has long dominated the market. Still, its potential toxicity, processing dust hazards, and environmental disputes have prompted the industry to seek better solutions. With China's export controls on antimony compounds, antimony trioxide is in short supply in the international market, and sodium antimonate (NaSbO₃) has attracted attention due to its unique chemical properties and replacement functions. The technical team of UrbanMines Tech. Ltd., combined with the actual use experience and replacement cases of sodium antimonate, compiled this article from a technical perspective, discussed with knowledgeable people in the industry the feasibility of sodium antimonate replacing Sb₂O₃, and analyzed its principles advantages, and disadvantages.

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I. Comparison of flame retardant mechanisms: synergistic effect of sodium antimonate and antimony trioxide

1. Flame retardant mechanism of traditional Sb2O2

Sb2O2 must work synergistically with halogen flame retardants (such as bromine compounds). During the combustion process, the two react to form volatile antimony halides (SbX2), which inhibit combustion through the following pathways:

Gas phase flame retardant: SbX₃ captures free radicals (·H, ·OH) and interrupts the chain reaction;

Condensed phase flame retardant: promotes the formation of carbon layer to isolate oxygen and heat.

2. Flame retardant properties of sodium antimonate

The chemical structure of sodium antimonate (Na⁺ and SbO₃⁻) gives it a dual function:

High temperature stability: decomposes to generate Sb₂O₃ and Na₂O at 300–500°C, and the released Sb₂O₃ continues to cooperate with halogens for flame retardancy;

Alkaline regulation effect: Na₂O can neutralize the acidic gases (such as HCl) produced by combustion and reduce the corrosiveness of smoke.

Key technical points: Sodium antimony releases active antimony species by decomposition, achieving a flame retardant effect equivalent to Sb2O₃ while reducing the risk of dust exposure during processing.

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II. Analysis of the advantages of sodium antimonate substitution

1. Improved environment and safety

Low dust hazard: Sodium antimonate is in granular or microspherical structure, and it is not easy to produce inhalable dust during processing;

Less toxicity controversy: Compared with Sb2O2 (listed as a substance of potential concern by EU REACH), sodium antimonate has less eco-toxicity data and is not yet strictly regulated.

2. Processing performance optimization

Enhanced dispersibility: Sodium ions increase polarity, making it easier to disperse evenly in the polymer matrix;

Thermal stability matching: The decomposition temperature matches the processing temperature (200–300°C) of common fibers (such as polyester and nylon) to avoid premature failure.

3. Multifunctional synergy

Smoke suppression function: Na₂O neutralizes acidic gases and reduces smoke toxicity (LOI value can be increased by 2–3%);

Anti-dripping: When compounded with inorganic fillers (such as nano clay), the carbon layer structure becomes denser.

III. Potential Challenges in the Application of Sodium Antimonate

1. Balance between cost and usage

High raw material cost: The synthesis process of sodium antimonate is complicated and the price is about 1.2–1.5 times that of Sb₂O₃;

Low effective antimony content: Under the same flame retardant level, the amount of addition needs to be increased by 20-30% (because the sodium element dilutes the antimony concentration). However, UrbanMines Tech. Ltd., with its unique R&D advantages, can optimize the production cost of sodium antimonate to be lower than antimony trioxide and quickly occupy a considerable part of the global market share in half a year.

2. Technical compatibility issues

pH sensitivity: Alkaline Na₂O may affect the melt stability of some resins (such as PET);

Hue control: Sodium residue at high temperatures may cause slight yellowing of the fiber, requiring the addition of colorants.

3. Long-term reliability needs to be verified

Difference in weather resistance: Sodium ion migration in hot and humid environments may affect flame retardancy durability;

Recycling challenges: The chemical recycling process for sodium-containing flame-retardant fibers needs to be redesigned.

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IV. Application scenario recommendations

Sodium antimonate is more suitable for the following fields:

1. High value-added textiles: such as fire-fighting uniforms and aviation interiors, which have strict requirements on smoke suppression and low toxicity;

2. Water-based coating system: taking advantage of its dispersibility to replace Sb₂O₃ suspension;

3. Composite flame retardant formula: compounded with phosphorus-nitrogen flame retardants to reduce halogen dependence.

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V. Future Research Directions

1. Nano-modification: Improve flame retardant efficiency by controlling particle size (<100 nm);

2. Bio-based carrier composite: combined with cellulose or chitosan to develop green flame-retardant fibers;

3. Life Cycle Assessment (LCA): Quantify the environmental benefits of the entire industry chain.

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Conclusion

As a potential substitute for antimony trioxide, sodium antimonate shows unique value in terms of environmental friendliness and functional integration, but its cost and technical adaptability still need to be improved. With stricter regulations and process optimization, sodium antimonate is expected to become an important option for the next generation of fiber flame retardants, driving the industry to evolve towards high efficiency and low toxicity.

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Keywords: sodium antimonate, antimony trioxide, flame retardant, fiber treatment, smoke suppression performance