Shandong Huashang Chemical Co., Ltd. is a high-tech enterprise specializing in the research and development, manufacturing, and sales of fine chemicals. Headquartered in Jinan, Shandong, China, we are committed to delivering high-quality products to our global partners. Currently, over 90% of our products are exported to developed markets, including North America, Europe, Japan, South Korea, and the Middle East.
Product Description
Insoluble sulfur, also known as polymeric sulfur or μ-sulfur (CAS: 9035-99-8), is an inorganic polymeric allotrope of elemental sulfur with the linear formula (S)?. It appears as a yellow, non-dusting powder at room temperature, odorless or with a faint oily odor derived from trace impurities. The compound is insoluble in carbon disulfide, water, and most organic solvents (such as ethanol, ether, and chloroform), which distinguishes it from ordinary soluble sulfur. It is produced by the thermal polymerization of common sulfur, with a molecular weight of approximately 30,000, exhibiting typical viscoelastic properties of polymers. As a high-polymeric sulfur, it depolymerizes into soluble sulfur at standard vulcanization temperatures (120–150 °C), enabling effective cross-linking in rubber compounds and making it an indispensable additive in the rubber industry.
Uses
Rubber Vulcanizing Agent: Its primary application is in the rubber industry, especially for radial tires (all-steel and semi-steel), tire carcass compounds, cushion compounds, and white sidewall rubbers. It effectively prevents blooming (sulfur migration to the rubber surface), enhances steel-rubber adhesion, and improves the heat resistance, wear resistance, and fatigue resistance of tires, thereby extending the service life of rubber products.
Industrial Rubber Products: Widely used in the production of hoses, conveyor belts, cables, rubber rollers, oil seals, and rubber shoes. It ensures uniform sulfur distribution in the rubber matrix, maintains consistent vulcanization quality, and improves the overall mechanical properties of rubber products, such as tensile strength and elongation at break.
Light-Colored Rubber Goods: Due to its non-discoloring and non-staining properties, it is ideal for light-colored and transparent rubber products. Unlike ordinary soluble sulfur, it does not cause discoloration of rubber surfaces, making it suitable for products that require high appearance quality, such as white rubber accessories and decorative rubber parts.
Specialty Rubber Compounds: Employed in sulfur-rich rubber compounds where the sulfur loading exceeds the solubility limit of ordinary sulfur. It can be mixed with soluble sulfur to adjust the vulcanization rate and cross-linking density, meeting the special performance requirements of high-sulfur rubber products.
Molecular Formula & Structure
- Molecular Formula: (S)? (n ≈ 1000, the degree of polymerization varies with production process)
- Molecular Weight: ~30,000 g/mol (varies with the degree of polymerization)
- IUPAC Name: Polymeric sulfur
- Synonyms: μ-Sulfur; Elastic sulfur; Insoluble polymeric sulfur; MFCD00134045; BRN 8008572; PubChem Substance ID: 24868462; EC Number: 215-671-0
- EC Number: 215-671-0
- CAS Number: 9035-99-8
- SMILES Code: S(S)S (n polymeric chain)
- Chemical Structure: It has a high-polymeric chain structure composed of sulfur atoms, forming a linear polymer with a helical conformation. The polymer is metastable at room temperature and gradually converts to soluble rhombic sulfur over time (50% conversion in weeks), and this conversion is accelerated at higher temperatures (minutes at 80 °C). In industrial production, stabilizers (such as mineral oil, antioxidants) are usually added to slow down the depolymerization process and extend its storage life.
Physical & Chemical Properties
- Appearance: Yellow, free-flowing, non-dusting powder; the particle size varies according to the product grade, usually 10–150 μm.
- Melting Point: 112.8–120 °C (depolymerizes during melting); Boiling Point: 444.6 °C (decomposes); Flash Point: 207 °C (closed cup); it is a combustible solid, and burning produces sulfur dioxide (SO?) gas with a pungent odor.
- Density: ~2.07 g/cm3 (25 °C); Bulk Density: 0.8–1.2 g/cm3; Solubility: Insoluble in water, carbon disulfide, ethanol, ether, and chloroform; sparingly soluble in benzene and toluene.
- Stability: Metastable at room temperature; depolymerizes to soluble sulfur at vulcanization temperatures (120–150 °C); sensitive to high temperature and moisture. It is stable under cool, dry, and sealed conditions; moisture and high temperature will accelerate its depolymerization.
- Toxicity: Non-toxic; low acute oral toxicity (LD?? > 5000 mg/kg in rats); high concentrations of dust may cause mild eye and respiratory irritation, but no long-term toxic effects. It is non-toxic to aquatic organisms but may cause slight environmental impact if discharged in large quantities.
Synthesis & Storage
- Synthesis: The main production method is thermal polymerization of ordinary sulfur. Common sulfur is heated to 200–250 °C for polymerization reaction, and then rapidly quenched in water or organic solvents to fix the polymeric structure. The product is then stabilized with oil (19–21% oil content for standard grades such as HD OT20/HS OT20) and additives (antioxidants, anti-caking agents) to prevent depolymerization and improve fluidity. Finally, it is crushed and sieved to obtain products of different particle sizes.
- Storage: Store in a cool, dry, well-ventilated warehouse, with a recommended temperature ≤25 °C. It should be packed in sealed, moisture-proof containers (such as polyethylene plastic bags or paper-plastic composite bags) with a net weight of 25 kg per bag. Avoid direct sunlight, high temperature, and moisture; keep away from oxidizing agents, strong acids, and open flames. Store separately from food and beverages. Shelf life: 6–12 months when unopened and stored properly; use promptly after opening to prevent depolymerization and caking.
- Safety: Wear nitrile gloves, safety goggles, and a dust mask during handling to avoid inhalation of dust and eye contact. Operate in a well-ventilated area to prevent dust accumulation and dust cloud formation (which may cause combustion hazards). In case of skin contact, rinse the affected area with plenty of water; in case of eye contact, rinse cautiously with water for several minutes. In case of fire, use dry sand, carbon dioxide fire extinguishers to put out the fire, and avoid using water to prevent splashing of burning sulfur.
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