Superdrawing of polytetrafluoroethylene nascent powder by solid‐state coextrusion

Sawai, Daisuke; Watanabe, Daisuke; Morooka, Naoyuki; Kuroki, Haruka; Kanamoto, Tetsuo

doi:10.1002/polb.20988

Cited by 12 publications

(13 citation statements)

References 36 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…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%

“…The pronounced crystallization rate due to few entanglement couplings was observed at fiber spinning for nascent powders of polyethylene, poly(tetrafluoroethylene), and poly(acrylonitrile). [39][40][41][42] Rapid crystallization from the ordered melt, which has few entanglement couplings, was also detected for isotactic PP, recently. 43 As similar to these phenomena, the drawdown force enhancement for a long die could be attributed to the rapid crystallization because of few entanglement couplings.…”

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

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

et al. 2014

View full text Add to dashboard Cite

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.

show abstract

Section: Resultsmentioning

confidence: 85%

Section: Resultsmentioning

confidence: 99%

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

et al. 2014

View full text Add to dashboard Cite

show abstract

“…At yet higher EDR's the strength rapidly decreased with increasing EDR due to the formation of flaws. 28 The maximum strength achieved was 410 MPa for the SSCE at a T ext ¼ 170 C and an EDR = 10, at a T ext ¼ 190 C and an EDR = 12, and at a T ext ¼ 200 C and an EDR = 16. The elongation at break decreased with increasing EDR.…”

Section: Resultsmentioning

confidence: 99%

“…At yet higher EDR, the tensile modulus decreased rapidly for SSCE at T ext 's = 190 and 200 C due to the formation of flaws detected by an optical microscope. 28 The maximum modulus of 9.5 GPa was achieved by SSCE of a cast sc-film at a T ext ¼ 200 C and an EDR of 16. At the highest T ext of 210 C, the modulus increased more slowly but steadily with EDR and the maximum modulus of 7.5 GPa was achieved at the highest EDR of 19.…”

Section: Resultsmentioning

confidence: 99%

Development of Oriented Morphology and Mechanical Properties upon Drawing of Stereo-Complex of Poly(L-lactic acid) and Poly(D-lactic acid) by Solid-State Coextrusion

Sawai

Tamada

Kanamoto

2007

Polym J

Self Cite

View full text Add to dashboard Cite

ABSTRACT:A semicrystalline film consisting of only stereo-complex (sc) crystals was prepared by casting from a solution of an equimolar blend of poly(L-lactic acid) (PLLA) and poly(D-lactic acid) (PDLA). The film was uniaxially drawn by solid-state coextrusion, and the development of oriented morphology and mechanical properties was investigated by DSC, WAXD, dynamic mechanical analyses and tensile tests. The ductility increased with extrusion temperature (T ext ), reached a maximum at a T ext of 200 C, and at yet higher T ext 's it rapidly decreased. The maximum tensile modulus and strength of 9.5 GPa and 410 MPa, respectively, were achieved for a highly drawn sc-film prepared by coextrusion at a T ext of 200 C and EDR of 16. Such a drawn film consisted of highly oriented sc-crystals and had a crystallinity of c ¼ 59 wt % and a high chain orientation function of f c ¼ 0:993. The oriented sc-films exhibited remarkably enhanced heat-resistance compared to the oriented films of PLLA homo-polymer. The dynamic storage modulus of a sc-film with an EDR of 16, measured at 11 Hz, was 9.5 GPa at room temperature and 2.7 GPa even at 200 C, 20-25 C above the melting temperatures of -and -form homo-crystals. The high thermal stability of oriented sc-films was primarily ascribed to the high melting temperature and weak -relaxation intensity for the sc-films compared to the PLLA films. No existence of a crystalline relaxation in the sc-films also contributed to improve their thermal stability. Poly(L-lactic acid) (PLLA) attracts considerable interest from both fundamental and industrial viewpoints because it can be synthesized from renewable resources, such as corn and potato.1-3 Since PLLA is biodegradable and biocompatible, this polymer has been used for biomedical applications.4-6 Because PLLA has fairly good mechanical properties with a high melting temperature (T m ¼ 170{180 C), its application for more general purposes as an environmentally friendly and economically feasible polymer has been evaluated. [7][8][9] PLLA commonly crystallizes into two crystal modifications; i.e., the -and the -forms, 10-12 both of which have a melting temperature around 170-180 C. It has been reported that an equimolar blend of PLLA and poly(D-lactic acid) (PDLA) forms a mixture of stereo-complex crystals and -form homocrystals when it was crystallized from solutions and melt, depending on the crystallization conditions. 13,14 Homo-crystals, such as -form and -form crystals consist of only PLLA or PDLA molecules, whereas the sc-crystal is composed of PLLA and PDLA chains with opposite helical hand packed side by side. It is interesting to note that the sc-crystal shows a melting temperature of 220-230 C, which is about 50-60 C higher than those for the homo-crystals. Recently, Kimura et al. 15,16 found bacteria which produces Dlactic acid from glucose. This finding may allow to produce D-lactic acid more easily at a lower coast and enhance the application of sc-poly(lactic acid).It has been reported that when an equimolar blend of PLLA and ...

show abstract

“…Polymers with lowered density of entanglements can be drawn to very large deformation ratio. Three different approaches were proposed for limitation of the entanglements of macromolecules in amorphous phase of solid polymer: (a) crystallization under pressure with formation of extended chains crystals [available only for certain polymers, e.g., high density polyethylene (HDPE), polyamides], (b) crystallization during polymerization [e.g., poly(tetrafluoroethylene) (PTFE), polyethylene (PE))], (c) crystallization from dilute solution (polyolefins) …”

Section: Introductionmentioning

confidence: 99%

Deformation of disentangled polypropylene crystalline grains into nanofibers

Krajenta

Pawlak

Gałęski

2016

J Polym Sci B Polym Phys

View full text Add to dashboard Cite

It was shown that a solid‐state deformation of polypropylene (PP) being in the form of partially disentangled powder is possible by blending with another molten polymer. During mixing of disentangled polypropylene powder with polystyrene at the temperature below melting of polypropylene crystals the shear forces deform powder grains into nanofibers. All disentangled powder particles larger than 0.7 µm underwent deformation into nanofibers having the mean thickness between 100 and 200 nm. Polypropylene nanofibers got entangled during blending and form a network within polystyrene matrix, reinforcing it. Network of entangled nanofibers can be further deformed with pronounced strain hardening and strength reaching 70 MPa at 135 °C. Blending resulted in generation of PP nanofibers and formation of PP nanofibers entangled network, thus formation of “all‐polymer nanocomposites” in one step compounding. The crucial feature for ultra‐deformation of PP grains by shearing during mixing is disentanglement of macromolecules. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1983–1994

show abstract

Superdrawing of polytetrafluoroethylene nascent powder by solid‐state coextrusion

Cited by 12 publications

References 36 publications

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

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

Development of Oriented Morphology and Mechanical Properties upon Drawing of Stereo-Complex of Poly(L-lactic acid) and Poly(D-lactic acid) by Solid-State Coextrusion

Deformation of disentangled polypropylene crystalline grains into nanofibers

Contact Info

Product

Resources

About