The continuous production of ultra-high-molecular-weight polyethylene (UHMWPE) filaments was studied by the direct roll forming of nascent reactor powders followed by subsequent multistage orientation drawing below their melting points. The UHMWPE reactor powders used in this study were prepared by the polymerization of ethylene in the presence of soluble magnesium complexes, and they exhibited high yield even at low reaction temperatures. The unique, microporous powder morphology contributed to the successful compaction of the UHMWPE powders into coherent tapes below their melting temperatures. The small-angle X-ray scattering study of the compacted tapes revealed that folded-chain crystals with a relatively long-range order were formed during the compaction and were transformed into extended-chain crystals as the draw ratio increased. Our results also reveal that the drawability and tensile and thermal properties of the filaments depended sensitively on both the polymerization and solid-state processing conditions. The fiber drawn to a total draw ratio of 90 in the study had a tensile strength of 2.5 GPa and a tensile modulus of 130 GPa. Finally, the solid-state drawn UHMWPE filaments were treated with O-2 plasma, and the enhancement of the interfacial shear strength by the surface treatment is presented. (c) 2005 Wiley Periodicals, Inc.