Solid‐state compaction and drawing of nascent reactor powders of ultra‐high‐molecular‐weight polyethylene

Abstract

ABSTRACT:The continuous production of ultra-highmolecular-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 solidstate 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.

A study of oriented conductive composites with segregated network structure obtained via solid‐state processing of UHMWPE reactor powder and carbon nanofillers

“…The seeming discrepancy was attributed to the fact that the composites described in Refs. , and were prepared via hot pressing at temperature above the polymer melting point, thus allowing partial penetration of the conductive filler inside the polymer particles.…”

Локализация Моноклинной Фазы В Насцентных Частицах Сверхвысокомолекулярного Полиэтилена

“…В последнее время активно разрабатывается сухой (безрастворный) способ получения высокопрочных высокомодульных нитей непосредственно из реакторного порошка (РП) сверхвысокомолекулярного полиэтилена (СВМПЭ), альтернативный дорогому и экологически небезопасному методу гель-технологии. Несмотря на то что в этой области достигнуты значительные успехи [1][2][3][4][5][6][7][8][9] и даже налажено коммерческое производство пленок Endumax (фирма Teijin-Aramid), прочностные характеристики производимого безрастворным методом материала все же остаются ниже (2.5 GPa), чем прочности коммерческих волокон СВМПЭ Dyneema (DSM, The Netherlands) и Spectra (Honeywell, USA), получаемые методом гель-технологии (3.7−4.7 GPa). Для получения высокопрочных пленочных нитей СВМПЭ сухим методом из реакторного порошка СВМПЭ сначала изготавливают монолитную заготовку, которую затем подверга-ют многоступенчатой ориентационной вытяжке при повышенной температуре.…”

A Novel Ziegler–Natta-Type Catalytic System—TiCl4/2,2′-Dimethoxy-1,1′-Binaphthalene/Et3Al2Cl3/Bu2Mg for Production of Ultrahigh Molecular Weight Polyethylene Nascent Reactor Powders, Suitable for Solvent-Free Processing

“…In the first approximation, systems based on TiCl 4 complexes with simple cyclic ethers, for example, TiCl 4 (THF) 2 and TiCl 3 (THF) 3 , can be classified as post-metallocene catalysts. These complexes, in the presence of organomagnesium and organoaluminum compounds, are moderately active in the polymerization of ethylene, and lead to the formation of UHMWPE powders which can be processed by the solid-phase method [17,18,19]. However, the organic ligands in these complexes can occupy any of the six sites in the octahedron and, thereby, produce a certain set of active sites upon activation.…”