Robuta

https://www.arkema.com/global/en/products/product-finder/product/thiochemicals/heavy_mercaptans/nom/
Mercaptans (alone or blended) are commonly used as additives in the manufacturing process of several thermoplastics, elastomers or acrylic polymers.
chain transfermercaptansagentsnomarkema
https://www.astm.org/membership-participation/technical-committees/workitems/workitem-wk97923
ASTM International - Standards Worldwide
test methodrevisionstandardmercaptans