Structural formation of poly (ethylene terephthalate) during the induction period of crystallization: 1. Ordered structure appearing before crystal nucleation

Imai, Masayuki; Mori, Keiji; Mizukami, Tohru; Kaji, Keisuke; Kanaya, Toshiji

doi:10.1016/0032-3861(92)90399-h

Cited by 207 publications

(133 citation statements)

References 9 publications

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“…Similar behavior has been reported for the semirigid polymers poly(ethylene terephthalate) (PET) and poly(ether ether ketone) (PEEK) crystallized by heating from an amorphous glassy state 4 • 5 . Figure 4 shows the time evolution of the logarithm of the normalized integrated SAXS intensity l(t)/ 1(0) in the range 0.12<q< l.15nm-1 at Tc=265, 267, and 270°C.…”

Section: Precursors Of Crystallizationsupporting

confidence: 54%

Density Fluctuations as Precursors of Crystallization in a Thermoplastic Polyimide

Ania

Cagiao

Calleja

1999

Polym J

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ABSTRACT:The present report is part of a general study aiming to investigate the possible evidence of electron density fluctuations as precursors of crystallization in polymers with different chain stiffness. The present experiments on the thermoplastic polyimide (New-TPI) with varying induction times, studied by small-and wide-angle X-ray scattering (SAXS and W AXS), reveal the onset of long-range ordering prior to crystal growth. Slow crystallization, slightly above T, indicates the development of well resolved SAXS patterns associated with long range order before the development of crystalline peaks in the W AXS region. The experimental results suggest that density fluctuations control at sufficiently low temperatures the precrystallization mechanisms during the embryonic period.KEY WORDS Electron Density Fluctuations / Simultaneous Small-Angle X-Ray Scattering and Wide-Angle X-Ray Scattering/ Cold Crystallization/ New-Thermoplastic Polyimide / The development of crystallinity in the amorphous thermoplastic polyimide (New-TPI) has been studied, in detail, using differential scanning calorimetry, wideand small-angle X-ray scattering (WAXS and SAXS) 1 · 2 and microhardness, 3 by cold crystallization from the amorphous state. Preceding SAXS studies show that during cold crystallization, New-TPI develops a periodic structure with crystals a few molecular repeat-units thick. 1 · 2 Time resolved SAXS studies reveal, in addition, that both, long period and lamellar thickness show a decreasing dependence with time. Cold crystallization kinetics from DSC has been described by a single A vrami exponent, n = 3.5. 2 The study of the crystallization mechanism during the embryonic period of TPI is, however, still missing. The ordering process prior to crystallization has been studied for semirigid 4 · 5 and flexible 6 polymers by means of simultaneous real time W AXS and SAXS. In these systems phase separation has been shown to follow spinodal decomposition. The latter involves two regions of the polymer, one having the appropriate chain conformation for crystallization and the other one which becomes the amorphous regions present in all semicrystalline polymers. Recent morphological studies on poly(ethylene 2,6 dicarboxylate naphthalene) (PEN) support the above view evidencing, during the induction period prior to crystallization, a phase separation into crystallizable and non-crystallizable regions. 7 If spinodal decomposition prevails, development of the SAXS pattern due to density fluctuation occurs prior to any WAXS from the crystals. This is due to the continuous transformation of the partially ordered phase through slightly more ordered states. 8 The object of the present report is to extend the above studies aiming to investigate the possible evidence of density fluctuation as precursors of crystallization in New-TPI, polymer with the highest chain stiffness so far investigated. EXPERIMENTALAmorphous thermoplastic polyimide resin (New-TPI) from Mitsui Chemical Co. was used as supplied,9 Two transparent 80 µm thick ...

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Section: Precursors Of Crystallizationsupporting

confidence: 54%

Density Fluctuations as Precursors of Crystallization in a Thermoplastic Polyimide

Ania

Cagiao

Calleja

1999

Polym J

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“…The discussion regarding chain stretching is therefore not applicable to these polymer systems. Actually, the nucleation dynamics of PET is similar to the phase transition observed in liquid crystalline polymers under quiescent (Imai et al 1992(Imai et al , 1993(Imai et al , 1995 and flowing conditions (Welsh et al 1998(Welsh et al , 2000. Smectic ordering is also suggested to be of importance for the nucleation of iPP by Li and de Jeu (2003).…”

Section: Phase Change Dynamicsmentioning

confidence: 77%

Towards a rheological classification of flow induced crystallization experiments of polymer melts

2004

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“…Experimental observations of a SAXS signal intensity increase, before the onset of a WAXS signal (i.e., crystal Bragg peaks), during the very early stages of crystallization were reported for PET, [28][29][30][31] iPP, 32,33 and PE. 34 This was claimed to be due to a precrystalline orientation in the melt and was sometimes explained on the basis of linearized Cahn-Hilliard theory of spinodal decomposition.…”

Section: Mesomorphic Meltmentioning

confidence: 99%

Crystallization and melting of polyethylene copolymers: Differential scanning calorimetry and atomic force microscopy studies

Mirabella

2006

J Polym Sci B Polym Phys

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ABSTRACT:The HoffmanLauritzen theory of secondary, surface nucleation and growth was primarily relied upon for about 40 years after its introduction in about 1960 to rationalize the crystallization of flexible chain polymers into lamellar crystals. However, in about 1998, Strobl and coworkers introduced a different model for crystallization, based on the stagewise formation of lamellae. Two major components of this model were as follows: (1) the concept of the formation of a mesomorphic melt as a precursor to crystallization and (2) the control of the melting temperature range of lamellar crystals of homogeneous polyolefin copolymers by an inner degree of order or perfection rather than on the crystal thickness. The first concept is in disagreement with the HL theory and the second with the Gibbs-Thomson theory, which associates melting temperature with lamella thickness. In the present study, differential scanning calorimetry and atomic force microscopy were successfully employed to monitor the in situ quiescent crystallization of polyethylene homopolymer and copolymer. In the present study, evidence was not found to support the concept of lamellae with equal thickness melting over a broad temperature range. Some evidence was found that might be interpreted to support the concept of a mesomorphic melt as a precursor to crystallization. At present, the model promoted by Strobl and coworkers appears to be at an uncertain stage at which strong proof or disproof are not available. However, this alternative model has injected a new vitality into the study of crystallization of flexible chain polymers.

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Structural formation of poly (ethylene terephthalate) during the induction period of crystallization: 1. Ordered structure appearing before crystal nucleation

Cited by 207 publications

References 9 publications

Density Fluctuations as Precursors of Crystallization in a Thermoplastic Polyimide

Density Fluctuations as Precursors of Crystallization in a Thermoplastic Polyimide

Towards a rheological classification of flow induced crystallization experiments of polymer melts

Crystallization and melting of polyethylene copolymers: Differential scanning calorimetry and atomic force microscopy studies

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