Between 60 and 70% of all propylene oxide is converted to polyether polyols by the alkoxylation process. These polyols are building blocks in the production of polyurethane plastics. About 20% of propylene oxide is hydrolyzed into propylene glycol, via a process that is accelerated by acid or base catalysis. Other major products are polypropylene glycol, propylene glycol ethers, and propylene carbonate.