Impact-resistant graft copolymers prepared by grafting a styrene, acryl or mixture of styrene-type and acryl polymers or copolymers onto a multiply unsaturated polymer based on ethylene, as a terpolymer of ethylene, propylene and other multiply unsaturated monomers (EPDM-rubbers) in the presence of a radicalforming peroxydi-carbonate initiator is disclosed. Graft copolymers so produced are impact-resistant, resist aging and are useful in forming tubes, films and bottles.