الكبريت غير القابل للذوبان IS-7020: لماذا يحدث التفتح

Blooming — a whitish powder appearing on the surface of uncured rubber — is one of the most reported complaints from buyers, and in steel-belted compounds the cause is frequently sulphur migration.

Why insoluble sulphur exists

Ordinary (soluble) sulphur is crystalline S8, which is partly soluble in rubber. At the high loadings needed for steel cord adhesion, that dissolved sulphur migrates to the surface and crystallises: the compound loses tack and buildability. Insoluble sulphur is polymeric sulphur that does not dissolve in rubber, so it stays where it was mixed.

What IS-7020 means

"IS" denotes insoluble sulphur and the number indicates the insoluble content as a percentage. Grades are also rated for thermal stability — the temperature at which the polymeric form converts back to soluble S8.

The handling rules that matter

• •Keep storage below roughly 40 °C. Above that, conversion to soluble sulphur accelerates and the product loses its purpose.
• •Keep mixing temperature below about 110 °C and add the sulphur late in the cycle.
• •Avoid contact with certain amines and accelerators in masterbatch storage, which promote conversion.
• •Use stock within the supplier's stated shelf life, typically six to twelve months from production.

If bloom appears, check storage temperature history and mix dump temperature before changing the formulation. ## Need the documents or today's price? Send us the grade, quantity and destination port — we return a quotation with COA and MSDS attached. Email manager@fipolymer.com or use the inquiry form on this site.