Insoluble sulfur, also known as amorphous sulfur, is a homopolymer of sulfur and an efficient rubber vulcanizing agent. CAS 7704-34-9 and 9035-99-8 represent two distinct chemical substances, and their relationship lies primarily in the fact that they are different forms or products of sulfur, each exhibiting unique physical and chemical properties as well as distinct areas of application.
Insoluble sulfur, a non-toxic, flammable yellow powder named for its insolubility in carbon disulfide, is a specialized product offered by sulphur powder suppliers. Before the vulcanization process, this material remains insoluble within rubber compounds but dissolves effectively during vulcanization to fulfill its critical vulcanizing function. Manufactured through the thermal polymerization of ordinary sulfur, insoluble sulfur boasts a molecular weight of approximately 30,000. Its unique viscoelasticity and molecular weight distribution, characteristic of high polymers, have earned it the alternate names of elastic sulfur and polymeric sulfur, positioning it as a vital inorganic polymer chemical raw material.
Insoluble sulfur is primarily used as an advanced accelerator and vulcanizing agent in the rubber industry, extensively applied in the production of tires and other rubber composite products, such as carcass compound, cushion gum, white sidewall compound, retreading tires, rubber hoses, adhesive tapes, and rubber compounds bonded with reinforcing materials. It is also used in rubber compounds for cables, rubber rollers, oil seals, rubber shoes, and light-colored rubber products that require a large amount of sulfur.
Thanks to its ability to strengthen the adhesion between radial plies, steel cords, and rubber, insoluble sulfur effectively prevents blooming, enhances the heat resistance and wear resistance of tires, and reduces the risk of premature vulcanization. It is suitable for critical rubber products like steel cord tires, with usage amounts equal to those of ordinary sulfur.
Radial tires vulcanized with insoluble sulfur exhibit excellent wear resistance, long service life, and energy efficiency. As a filler in high-pressure lubricants and cutting oils, it improves the load-bearing capacity and film strength of oils. It is also applied in oil tank coatings resistant to oil, chemical corrosion sealants, resin and cement modification, and nitrile rubber modification. Besides being indispensable in radial tires, insoluble sulfur is also used in high-quality products made from natural and synthetic rubbers. Furthermore, it finds applications in dyes, textiles, pesticide production, and the treatment of heavy metal wastewater.