Ultradrawing of ultrahigh molecular weight polyethylene reactor powders prepared by highly active catalyst system

Sano, Akira; Iwanami, Yoshimu; Matsuura, Kazuo; Yokoyama, Shigeo; Kanamoto, Tetsuo

doi:10.1016/s0032-3861(00)00899-5

Cited by 24 publications

(12 citation statements)

References 24 publications

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“…Since the decrease in the entanglement density enhances the chain diffusion onto the crystal surface, the crystallization rate is greatly enhanced as demonstrated by Seemork et al . Similar phenomena were observed at a fiber spinning process for nascent powders of ultra‐high‐molecular‐weight polyethylene, polytetrafluoroethylene, and polyacrylonitrile, and crystalline phase‐transformation from β‐form to α‐form of PP . Since the rapid crystallization leads to a reduced molten area in a strand, the actual strain rate in the deformable part increases after passing through a long die.…”

Section: Resultssupporting

confidence: 53%

Enhancement of drawdown force in polypropylene containing nucleating agent

Phulkerd

Nakabayashi

Iwasaki

et al. 2018

J of Applied Polymer Sci

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The effect of the nucleation efficiency of three commercial nucleating agents, such as 1,3:2,4‐bis(3,4‐dimethylbenzylidene)sorbitol (DMDBS), sodium 2,2′‐methylene‐bis‐(4,6‐di‐tert‐butylphenyl)phosphate (SMBP), and magnesium silicate (talc), on the melt‐stretching performance of isotactic polypropylene (PP) is studied. It is found that the addition of 0.5 wt % of a nucleating agent enhances the crystallization temperature and that effect is pronounced for DMDBS and SMBP. Furthermore, DMDBS is more efficient than the other tested nucleating agents in enhancing the drawdown force, defined as a force required for stretching a molten strand. Nanofibers of DMDBS, which show significant alignment in the flow direction, are responsible for the rapid crystallization of PP in the flow field leading to an increase of drawdown force. The stretched strand shows a highly oriented structure in which the α‐form crystals orient to the flow direction. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47295.

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Section: Resultssupporting

confidence: 53%

Enhancement of drawdown force in polypropylene containing nucleating agent

Phulkerd

Nakabayashi

Iwasaki

et al. 2018

J of Applied Polymer Sci

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“…After passing the overshooting, the shear stress decreases by disentanglement and reaches to a plateau value, at which the entanglement density is in the steady state. [39][40][41][42] Rapid crystallization from the ordered melt, which has few entanglement couplings, was also detected for isotactic PP, recently. Moreover, a large shear strain, that is, a long residence time in the capillary die, is required to be a plateau value of the shear stress at a high Weissenberg number condition.…”

Section: Resultsmentioning

confidence: 85%

Effect of Die Geometry on Drawdown Force of Polypropylene at Capillary Extrusion

et al. 2014

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Drawdown force, defined as the force needed to stretch a polymer melt uniaxially at capillary extrusion, is investigated using isotactic polypropylene. In this study, we focus on the effect of die geometry on the drawdown force. As similar to the swell ratio, which decreases with increasing die length, the drawdown force is found to increase with the die length. A prolonged residence time in a long die leads to the marked orientation. Consequently, crystallization occurs rapidly after passing through a long die, which is confirmed by wide-angle X-ray measurements. Moreover, the rapid crystallization by the addition of a nucleating agent also enhances the drawdown force. C 2014 Wiley Periodicals, Inc. Adv Polym Technol 2015, 34, 21477; View this article online at wileyonlinelibrary.com.

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“…Therefore, a powder film of UHMW‐PE was initially drawn by solid‐state coextrusion4 (or calendaring for an industrial process12) to a low extrusion draw ratio (EDR) of 6–20, followed by the second‐stage tensile draw under controlled conditions to achieve higher draw (two‐stage draw4, 12). The high ductility of the reactor powder was ascribed to a low entangled state which was significantly affected by the polymerization conditions 2, 13…”

Section: Introductionmentioning

confidence: 99%

Superdrawing of polytetrafluoroethylene nascent powder by solid‐state coextrusion

Sawai

Watanabe

Morooka

et al. 2006

J Polym Sci B Polym Phys

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A film of nascent powder of polytetrafluoroethylene (PTFE), compacted below the ambient melting temperature (T m , 335 8C), was drawn by two-stage draw techniques consisting of a first-stage solid-state coextrusion followed by a second-stage solid-state coextrusion or tensile draw. Although the ductility of extrudates was lost for the secondstage tensile draw at temperatures above 150 8C due to the rapid decrease in strength, as previously reported, the ductility of extrudates increased with temperature even above 150 8C when the second-stage draw was made by solid-state coextrusion, reflecting the different deformation flow fields in a free space for the former and in an extrusion die for the latter. Thus, a powder film initially coextruded to a low extrusion draw ratio (EDR) of 6-20 at 325 8C was further drawn by coextrusion to EDRs up to $400 at 325-340 8C, near the T m . Extremely high chain orientation (f c ¼ 0.998 6 0.001), crystallinity (96.5 6 0.5)%, and tensile modulus (115 6 5 GPa at 24 8C, corresponding to 73% of the X-ray crystal modulus) were achieved at high EDRs. Despite such a morphological perfection and a high modulus, the tensile strength of a superdrawn tape, 0.48 6 0.03 GPa, was significantly low when compared with those (1.4-2.3 GPa) previously reported by tensile drawing above the T m . Such a low strength of a superdrawn, high-modulus PTFE tape was ascribed to the low intermolecular interaction of PTFE and the lack of intercrystalline links along the fiber axis, reflecting the initial chain-extended morphology of the nascent powder combined with the fairly high chain mobility associated with the crystal/crystal transitions at around room temperature.

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Ultradrawing of ultrahigh molecular weight polyethylene reactor powders prepared by highly active catalyst system

Cited by 24 publications

References 24 publications

Enhancement of drawdown force in polypropylene containing nucleating agent

Enhancement of drawdown force in polypropylene containing nucleating agent

Effect of Die Geometry on Drawdown Force of Polypropylene at Capillary Extrusion

Superdrawing of polytetrafluoroethylene nascent powder by solid‐state coextrusion

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