Thiourea Dioxide (TDO / FAS)

Backed by over 40 years of manufacturing experience dating back to 1983, Yantai Dasteck Chemicals produces thiourea dioxide with a stable, fully controlled process. Every batch is released only after safety and performance testing, and is fully traceable. The product outperforms conventional reducing agents in both performance and storage safety.

Basic Information

Technical Index

Why Thiourea Dioxide Instead of Sodium Hydrosulfite

Thiourea dioxide is odorless and chemically stable at ambient conditions. It dissolves 26.7 g/L in water at 20°C (saturated solution pH 5.0) and stays stable in aqueous solution at 20–30°C; under thermal and alkaline conditions it gradually releases its reducing power as sulfinic acid.

Core Application Fields

• Textile printing & dyeing — vat dyeing, sulfur dyeing, wool & silk bleaching, reduction cleaning of disperse-dyed polyester, color stripping and vat cleaning. Delivers uniform whiteness without damaging fiber, and improves wash fastness of finished fabrics.
• Paper & pulp — reductive bleaching of mechanical pulp and deinking of waste paper (OCC / DIP). Removes chromophores while preserving pulp viscosity, raising brightness and tensile strength with mild fiber damage.
• Synthetic fiber manufacturing — stabilizer and reducing auxiliary to prevent fiber yellowing and optimize polymerization of polyester, polyamide and other synthetics.
• Kaolin processing — reductive bleaching of kaolin clay to remove iron impurities for high-whiteness coating, ceramic and filler grades.

Packing

• 25 kg / 80 kg net in kraft paper bags or plastic woven bags
• 50 kg fiber drum
• 500 kg jumbo bag

Storage and Handling

Store in a cool (below 30°C), dry and ventilated place. Avoid damp, direct sunlight and rain. Keep away from heat, sparks, flames, alkalis and oxidizing agents.

Frequently Asked Questions

• Is thiourea dioxide the same as thiourea? No — they are two different chemicals. Thiourea dioxide (CAS 1758-73-2) is a reducing agent; thiourea (CAS 62-56-6) is an intermediate for pharmaceuticals, rubber and mining. We manufacture both: see Thiourea.
• Is thiourea dioxide the same as FAS? Yes. FAS (Formamidine Sulfinic Acid) is the name commonly used in the pulp and paper industry for the same compound, CAS 1758-73-2.
• How does it compare with sodium hydrosulfite? Higher reduction potential (about -1230 mV vs -1080 mV), odorless, stable at room temperature, and typically dosed at 1/3 to 1/5 of the hydrosulfite amount for the same effect.