Insoluble sulfur (Su) is a non-toxic, flammable yellow powder, named for its insolubility in carbon disulfide. It is produced by the thermal polymerization of ordinary sulfur. Its molecular chain contains over 108 sulfur atoms, exhibiting the viscoelasticity and molecular weight distribution of polymers; therefore, it is also called elastic sulfur or polymeric sulfur, belonging to the category of inorganic polymeric chemical raw materials.
High Temperature Resistance: Insoluble sulfur maintains good stability at temperatures above 200°C, with a decomposition temperature typically above 230°C, approximately 50% higher than that of ordinary sulfur.
Aging Resistance: In oxygen aging tests in air at 150°C, insoluble sulfur exhibits superior aging resistance compared to ordinary sulfur. Especially after 500 hours of aging, hardness increases by approximately 10%, tensile strength decreases by approximately 5%, and elongation decreases by approximately 8%.
Controllability of Vulcanization Reaction: The relatively slow crosslinking rate of insoluble sulfur makes the vulcanization reaction more controllable, making it suitable for complex rubber formulations requiring long-term vulcanization.
Improved Mechanical Properties: By increasing the crosslinking density, insoluble sulfur significantly improves the mechanical properties of rubber, such as the tensile strength and tear strength of tire rubber.
Chemical Resistance: Insoluble sulfur significantly improves the acid, alkali, and oil resistance of rubber, making it suitable for chemical sealing, oilfield operations, and high-temperature corrosive environments.
