The terpolymerization of epichlorohydrin

ethylene oxide and propylene oxide was studied by using i-Bu3Al-H2O-Zn(acac)2 system as catalysts. The vulcanizates of the terpolymers have good properties in which low-temperature resistance is comparable to

while its oil resistance is superior to 18-nitrile

and its ozone resistance is much better than nitrile rubbers.