Hydroxyl-Ended Silicone Oil: D4 Opened with Potash, Then Water (Ceyzeriat 1964)

A trace of hot potash opens the ring of D4 and strings it into a long, thick chain. Water added a little at a time then cuts the chains back and leaves hydroxyl groups on their ends, which is what later lets the oil cure into rubber. This is Louis Ceyzeriat's oil A, the base of every sealant in his patent: 21,000 centistokes, 0.15 % hydroxyl. Source: L. Ceyzeriat (Rhône-Poulenc), US 3,133,891 (1964), column 4. His neutraliser was the precipitated silica Hi-Sil X303; we use our precipitated silica in its place. The potash mix and the equipment are ours. Picture drawn by Youblob.