The invention provides a copolymer of ethylene and at least 5 mol % of comonomer units derived from an alkyl acrylate or alkyl methacrylate, wherein the copolymer has a melt index of from 1 to 10,000 g/10 min, and a maximum peak melting temperature of at least 100.degree. C. The alkyl group of the alkyl acrylate or alkyl methacrylate can be a linear or branched C.sub.1 to C.sub.12 group, particularly n-butyl. The copolymer shows increased heat resistance as characterized by a temperature required to melt 50% of the copolymer of at least 80.degree. C., a temperature required to melt 80% of the copolymer of at least 100.degree. C., a temperature required to melt 100% of the copolymer of at least 110.degree. C. The invention further provides a process for copolymerizing ethylene and an alkyl acrylate or alkyl methacrylate comonomer.