Polymers comprising units derived from ethylene, said polymer having: a) a Melt Index of from 0.05 to 20 g/10 min. as determined by ASTM-1238 Condition E; b) at least 10 per 1000 C-atoms of short chain branches, containing five carbon atoms or less, as determined by C13 NMR, and less than 3.5 mol %, of units derived from a copolymerizable ethylenically unsaturated ester; c) a density of from 0.90 to 0.94 g/cm.sup.3, preferably 0.91 to 0.935 g/cm.sup.3, especially 0.92 to 0.93 g/cm.sup.3 as determined by ASTM D1505; and d) a relaxation time as described herein of at least 10 s. Such polymers can be obtained by free radical polymerization using a chain transfer agent that incorporates into the polymer chain such as an alpha-olefin, preferably propylene, as a chain transfer agent, preferably in a tubular reactor under circumstances to favor LCB formation in a down stream part of the tubular reactor.