Deformability of molten ultra-high molecular weight polyethylene (UHMWPE) was studied in the plane-strain compression at the temperature from a range of 145-165 degrees C. Two grades of UHMWPE were testeda commercial one synthesized in a slurry process with conventional Ziegler-Natta catalyst and the material polymerized in solution at low temperature using a homogeneous metallocene catalyst. These grades differ markedly in the initial concentration of chain entanglements in nascent powders. Specimens used for compression were produced either by compression molding or compaction of the nascent powders (sintering) at the temperature up to 130 degrees C in order to obtain a set of samples with a range of chain entanglement concentration. Plane-strain compression tests demonstrated a rubber-like behavior and a good deformability of molten samples in the temperature range of 145-155 degrees C. The ultimate true strain up to e = 3 was observed in samples prepared by compression molding, while for sintered samples of metallocene polymer it exceeded e = 4.3 (deformation ratio, ? > 74). At higher temperature of 165 degrees C deformation became unstable. A strong correlation between topological structure of the melt and its deformation behavior was found: highly disentangled samples (from nascent powder of metallocene polymer) tend to deform to much higher strain than samples of lightly reduced concentration of chain entanglements (from nascent powder of commercial Z-N polymer) or samples with entanglement density close to an equilibrium (prepared by compression molding), which demonstrated the lowest ultimate strain. The obtained results point out a new route of melt-processing of UHMWPE nascent powders for fabrication of ultra-strength fibers, alternative to the gel-spinning technology. (C) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012