Commonly used vulcanizing agents for rubber: classification of sulfur
(1) Powdered sulfur
Sulfur powder can be obtained after the massive sulfur is crushed and deacidified. The fineness of powder sulfur used in the rubber industry is below 200 mesh, and in special cases, it is also useful about 600 mesh.

(2) sedimentation of sulfur
The sulfur and calcium hydroxide are heated together to generate calcium polysulfide compounds, and then dilute sulfuric acid is added to make the sulfur settle out. The average particle size of this sulfur is 1 to 5 microns, so it has excellent dispersibility in rubber and is used in the manufacture of advanced rubber products.

(3) Colloidal sulfur (high dispersibility sulfur)
In the presence of a dispersant, the powdered sulfur or precipitated sulfur is ground in a ball mill or a colloid mill to make a viscous substance, which is then dried and pulverized to make colloidal sulfur with a particle size of 1 to 3 microns. This sulfur is suitable for the production of latex products.

(4)Surface treated sulfur
A layer of oil or polyisobutylene is coated on the surface of the sulfur particles to prevent the sulfur particles from being surrounded by other compounding agents, which is conducive to dispersion. Using 2.5% oil and sulfur to make paste, the dispersion effect is also very good.

(5) Insoluble sulfur
Crystalline sulfur is heated to a molten state of 200-250°C, and then rapidly cooled at a low temperature of 20°C to obtain a transparent elastomer. This is the chain "polymer" sulfur represented by S8n.