Melt drawing of ultra-high molecular weight polyethylene: Comparison of Ziegler- and metallocene-catalyzed reactor powders

Phase Development Mechanism during Drawing from Highly Entangled Polyethylene Melts

“…[4][5][6] Disentangling the initially entangled chains is a key for enabling such high performance. Recently, a less-entangled state of PE chains has been achieved by controlling the synthesis conditions, [11] but it can also be achieved by processing alone, even from conventional entangled melts, as suggested in this study.…”

“…The samples can then be successfully melt-drawn up to a maximum draw ratio of 45-50 at the optimum temperature of 150 8C. [4][5][6] It is also suggested the strain-induced crystallization with disentanglement occurs during the draw from the melt. [4] However, the phase development mechanism assumed above can not be experimentally confirmed because both crystalline reflection and amorphous scattering are too weak to detect using a conventional X-ray source, especially at the initial stage of melt-drawing.…”

“…[9] The extended shish crystal formed during drawing from the melt exhibits the former spots, as previously reported for the melt-drawn UHMW-PE film. [5,6] The relative intensity change of each reflection is evaluated from the line profiles extracted along the equator for a series of the obtained WAXD patterns. Figure 2a duplicates these profiles as a function of processing time.…”

Nanowrinkled and Nanoporous Polyethylene Membranes Via Entanglement Arrangement Control

“…Oriented crystallization from the rubbery amorphous state is achievable even for linear polyethylene (PE), which has the simplest molecular architecture but an ultrahigh molecular weight (UHMW) of over 10 6 Da 2–10. Its higher melt viscosity enables ultradrawing, even above the melting temperature ( T m ) due to the large number of entanglements contained.…”

“…In contrast, such melt‐drawing is impossible for conventional PE with a normal MW of 10 5 Da or lower. Melt‐drawn UHMW‐PE exhibits superior mechanical properties with resultant cylindrical extended‐chain crystals (ECCs),2–4, 8 which completely differ from the transient crystallization during drawing of natural rubber.…”