Mystery manufacturing process - GIF

[KustomsbyKent]

While the exact material is unknown to me, the exact same equipment is used in processing rubber, and preparing it for molding. I'm assuming this is either latex or a raw rubber. The drums press and mix it into a smooth mixture. Then it would later be cut into sizable pieces for a molding process, as rubber needs to be cured at high temperatures to set it.
I have been in rubber processing/manufacturing plants in both the US and in China, so I've seen that first hand. In China, they were making parts for products we had designed. After the rubber is processed on those drums, then it is cut into strips, and then cut to fit the plate molds. Workers manually place the strips of raw rubber in the mold, then they are pressed and heated at the same time to cure the rubber, and then the worker removes the molded part and reloads it. Hot and repetitive work, but you can mold complicated parts with fairly simple tooling.