The crystallization of compounding ingredients that are usually present on the surface of stock, cured or uncured, are always accompanied by the migration of the substance from the bulk to the surface, this phenomenon is known as Blooming. Any ingredient which is soluble in rubber can undergo blooming. These additives are soluble in rubber at high temperature but when cools down it decreases the solubility which leads to the migration to the surface. Blooming results in reducing the thickness of the stock, which is not ideal in the manufacturing of the tires and belts.
How To Prevent Blooming In Rubber?
Sulphur blooming is one of the major issues tackled by the rubber industry using the insoluble sulphur. To complete the process while avoiding sulphur blooming, the insoluble sulphur is mixed in the compound and the processing temperature is kept below the transition point of sulphur.
That’s why insoluble sulphur is one of the most important components in the rubber industry.
Apart from sulphur, accelerators are the another reason that can cause blooming in rubber. EPDM and butyl rubber blooming vulcanizates are highly prone to accelerators that can bloom very quickly. To avoid the blooming of such accelerators, it is advised to use accelerators with higher solubility, or use a few different types of accelerators instead of just using a single accelerator with high concentration.