As with epichlorohydrin, propylene oxide can be homoploymerized (PO) in a ring opening reaction using Zn (alkyl)2/water, or Al(alkyl)3/water catalysts (3.560-3.562). It can also be coploymerized with allylglycidil ether to give the coploymer GPO,whic is the more important product of this class (3.563). Since GPO has double bonds, it can be crosslinked with sulphur and accelerators. GPO has the following