Fibroin is the silk protein (produced by the silkworm, Bombyx mori) and together with sericin makes up silk. Fibroin is transformed into silk fibres by the industrial spinning process.

What it is used for and where
Cosmetics  
Bulking agent. It regulates the water content, dilutes other solids, can increase the volume of a product for better flow, acts as a buffer against organic acids, helps to keep the pH of the mixture within a certain level.
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CAS: 9007-76-5