Crystal structure of the low temperature phase (II) of polytetrafluoroethylene

Weeks, James J.; Clark, Edward S.; Eby, R. K.

doi:10.1016/0032-3861(81)90316-5

Cited by 97 publications

(46 citation statements)

References 12 publications

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“…The spherical particles, constituted of extended-chain crystals which wrap around themselves, contain crystalline regions that are rich of defects and could correspond to our lowtransient crystalline component. That would agree with the literature about the lowering of the transition temperatures in the presence of reticular defects [4].…”

Section: Discussionsupporting

confidence: 88%

“…It is a general opinion that, below 19 ~ PTFE crystallizes in a very well ordered triclinic phase [1,3,4], whereas, between 19 and 30 ~ it gives a well known, only partially ordered hexagonal phase [1,2]. Lastly, above 30 ~ and up to the melting point (equilibrium melting temperature T~ = 332 ~ [5]), a pseudohexagonal very disordered phase is the stable one [1,2,5].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermal properties at room temperature of polytetrafluoroethylene

Villani

Pucciariello

1991

Journal of Thermal Analysis

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Section: Discussionsupporting

confidence: 88%

Section: Introductionmentioning

confidence: 99%

Thermal properties at room temperature of polytetrafluoroethylene

Villani

Pucciariello

1991

Journal of Thermal Analysis

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“…At temperatures below 19 ° C (phase II), PTFE has a well-ordered triclinic unit cell containing two helical chain stems with 13 6 symmetry. [ 21,22 ] At 19 ° C, the fi rst-order transition (from order to disorder) between phase II and IV occurs, which results in an unraveling of the helical conformation from the triclinic cell with 13 6 symmetry to a partially ordered hexagonal unit cell containing stems with 15 7 symmetry. [ 23,24 ] Further rotational disordering and untwisting of the helices occurs above 30 ° C leading to a pseudohexagonal unit cell (phase I) with long-range positional and orientational order as temperature increases.…”

Section: Resultsmentioning

confidence: 99%

An Alternative Route Towards Metal–Polymer Hybrid Materials Prepared by Vapor‐Phase Processing

Lee

Ischenko

Pippel

et al. 2011

Adv Funct Materials

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Transition metals incorporated into polymers lead to unusual or improved physical properties that significantly differ from those of purely organic polymers. A simple and practicable incorporation of diverse transition metals into any available polymer would make an important contribution to overcome some of the synthetic difficulties of metal‐polymer hybrid materials. Here, it is demonstrated that atomic layer deposition (ALD) can be a promising means to resolve some of those difficulties. It is found that even polytetrafluoroethylene (PTFE) with its great physical and chemical stability can be easily transformed into a transition metal–PTFE hybrid material simply by applying a metal‐oxide ALD process to PTFE. Upon metal incorporation into the PTFE, the molecular structure as well as mechanical properties (tensile behavior) of PTFE were observed to significantly change. For a better understanding of the changes to the material, experimental investigations using Raman spectroscopy, attenuated‐total‐reflection Fourier‐transform infrared spectroscopy, wide‐angle X‐ray diffraction, and energy‐dispersive X‐ray analysis were performed. In addition, with density functional theory calculations, potential bonding states of the incorporated metal into PTFE were modeled and predicted. The ALD‐based vapor‐phase approach for metal incorporation into a polymer could bring about rapid progress in the research area of metal–polymer hybrid materials.

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“…Peak assignments were made based on published X-ray data on undeformed PTFE powder, filaments and thin films [29][30][31][32][33].…”

Section: Discussionmentioning

confidence: 99%

In-situ Measurement of Crystalline Lattice Strains in Polytetrafluoroethylene

et al. 2007

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Strain measurements by neutron diffraction are employed as an in situ technique to obtain insight into the deformation modes of crystalline domains in a deformed semi-crystalline polymer. The SMARTS (Spectrometer for MAterials Research at Temperature and Stress) diffractometer has been used to measure the crystalline lattice displacements in polytetrafluoroethylene (PTFE) for crystalline phase IV (at room temperature) in tension and compression and for crystalline phase I (at 60°C) in compression. The chemical structure of PTFE, -(C 2 F 4 )-n , makes it ideally suited for investigation by neutron methods as it is free of hydrogen that results in limited penetration depths and poor diffraction acquisition in most polymers. Deformation parallel to the prismatic plane normals is shown to occur by inter-polymer chain compression with a modulus ∼10× bulk, while deformation parallel to the basal plane normal occurs by intra-polymer chain compression with a modulus ∼1000× bulk, corresponding with theoretical values for a PTFE chain modulus. Deformation parallel to the pyramidal plane normals is accommodated by interpolymer chain shear.

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Crystal structure of the low temperature phase (II) of polytetrafluoroethylene

Cited by 97 publications

References 12 publications

Thermal properties at room temperature of polytetrafluoroethylene

Thermal properties at room temperature of polytetrafluoroethylene

An Alternative Route Towards Metal–Polymer Hybrid Materials Prepared by Vapor‐Phase Processing

In-situ Measurement of Crystalline Lattice Strains in Polytetrafluoroethylene

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