Graft copolymers are prepared by exposing a mixture of a poly (alkyl acrylate), in which the alkyl portion contains no more than eighteen carbon atoms, and a monomer to high energy irradiation, the monomer being selected from alkyl acrylates and methacrylates in which the alkyl portion may be acyclic or cyclic and contains no more than eighteen carbon atoms, acrylonitrile, acrylic acid, styrene, ring-substituted styrenes containing no more than a total of twenty carbon atoms, hydroxy-substituted alkyl vinyl ethers in which the alkyl portion may be acyclic or cyclic and contains from two to eighteen carbon atoms and in which there are one or two hydroxy groups on the alkyl portion but never more than one hydroxy group on any one carbon atom and no hydroxy group is closer than two carbon atoms to the ether oxygen, alkanamidoalkyl vinyl ethers in which the non-vinyl portion contains from three to twenty-three carbon atoms, vinyl alkyl sulphides in which the alkyl portion contains no more than eighteen carbon atoms, hydroxy-substituted alkyl vinyl sulphides in which the alkyl portion contains from two to eighteen carbon atoms and in which there are one to two hydroxy groups on the alkyl portion but never more than one hydroxy group on any one carbon atom and no hydroxy group is closer than two carbon atoms to the sulphur atom, dialkylaminoalkyl vinyl sulphides in which the dialkyl portion attached to the amino nitrogen considered individually may contain up to eight carbon atoms and considered collectively may form a fiveto six-membered heterocyclic amino group with the amino nitrogen atom and in which the amino nitrogen atom is always tertiary and is connected to the sulphur atom by means of an alkylene group of two to eighteen carbon atoms, N-vinyl lactams and alkyl-substituted N-vinyl lactams containing from six to twenty carbon atoms, alkyl vinyl sulphones in which the alkyl portion contains no more than eighteen carbon atoms, N-vinylalkyleneureas containing from five to twelve carbon atoms, and N-vinyl-N1-aminoalkylalkylene ureas containing from seven to twenty carbon atoms. Reference has been directed by the Comptroller to Specification 820,120.ALSO:Graft copolymers are prepared by exposing a mixture of a poly(alkylacrylate), in which the alkyl portion contains no more than 18 carbon atoms, and a monomer to high energy radiation (see Group IV(a)). They may be used as additives to wax-containing lubricating oils, fuel oils and diesel fuel. The monomer is chosen from certain alkyl or cycloalkyl acrylates or methacrylates, acrylonitrile, acrylic acid, styrene, ring-substituted styrenes, hydroxy-substituted alkyl or cycloalkylvinyl ethers, alkanamidoalkyl vinyl ethers, vinyl alkyl sulphides, hydroxy-substituted alkyl vinyl sulphides, dialkylaminoalkyl vinyl sulphides, alkyl vinylsulphides wherein the alkyl group carries a heterocyclic nitrogen-containing substituent, N-vinyl lactams, alkyl-substituted N-vinyl lactams, alkyl vinyl sulphone, N-vinyl-alkylene ureas and N-vinyl-N1-amino-alkyl-alkylene ureas. Reference has been directed by the Comptroller to Specification 820,120.