Memory effects in polymers. I. Orientational memory in the molten state; its relationship to polymer structure and influence on recrystallization rate and morphology

Khanna, Y. P.; Reimschuessel, A. C.

doi:10.1002/app.1988.070350824

Cited by 63 publications

(41 citation statements)

References 2 publications

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“…Consequently, the significant increase in crystallization rate from the virgin to the first processed PA6 should be due to memory effects induced by injection molding. More detail information about this phenomenon has been reported elsewhere [21][22][23][24][25][26][27][28]. For the samples with more than one processing step, the raise of crystallization rate is attributed to the decrease in molecular weight.…”

Section: Crystalline Behaviormentioning

confidence: 95%

Influence of reprocessing on the mechanical properties and structure of polyamide 6

Lin

2007

Journal of Materials Processing Technology

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Section: Crystalline Behaviormentioning

confidence: 95%

Influence of reprocessing on the mechanical properties and structure of polyamide 6

Lin

2007

Journal of Materials Processing Technology

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“…T cc , which can be readily obtained from a differential scanning calorimetry (DSC) scan, is a very sensitive measure of this memory effect. [51][52][53] The memory effect can be attributed to the persistence in the melt of hydrogen-bonded crystalline nuclei, which influence the subsequent crystallization behavior as the melt is cooled. These nuclei can be fully destroyed only upon annealing for an extended time ($90 min) far above T m (280 8C for PA-6, 60 8C above T m ) 49 or by recrystallization of the polymer from solution.…”

Section: Melting Behaviormentioning

confidence: 99%

Hydrogen bonding, mobility, and structural transitions in aliphatic polyamides

Murthy

2006

J Polym Sci B Polym Phys

222

197

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Some salient results in nylon research are reviewed to identify the fundamental principles that are applicable to other strongly interacting or hydrogenbonded polymers, including proteins. The effects of hydrogen bonds on stress-, heat-, and solvent-induced changes in macroscopic properties are discussed. These data provide a window into the chain mobility and linkages between the crystalline and amorphous domains, both of which are important for any predictive model. The changes in the characteristics of the amorphous phase with the crystallinity and orientation require that it be modeled with at least two components: a rigid/immobile/ anisotropic component and a soft/ mobile/isotropic component. The deformation and shrinkage behavior of these polymers are discussed in terms of the relative contributions of the amorphous and crystalline domains and of the interactions between them. The premelting crystalline transition is accompanied by the merging of intersheet and intrasheet diffraction peaks in some nylons, as observed by Brill, and not in others even though the underlying mechanism that gives rise to these transitions, the onset of volume-increasing librational motion of the crystalline stems, is the same. Because the effects of the temperature, deformation, and solvent have a common origin associated with mobility, a fictive temperature can be associated with a given solvent activity or stress level. The magnitude of this fictive temperature is the amount by which the glass or Brill transition temperature is reduced in the presence of solvents ($50 8C) or stress or by which the annealing temperature can be reduced in the presence of a solvent (or active stress) to achieve the same structural state as that of a dry (or static) polymer.

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“…This point is discussed in the section in which the results obtained with PET/PA12 blends are presented. Memory effect in polymers, more specifically the so-called orientational memory in the molten state, was studied earlier by Keller and Marchin [26] and more recently by Khanna and Reimschussel [27]. In their studies on some neat polymers employing mostly differential scanning calorimetry (DSC) and light microscopy, Khanna and Reimschussel pointed out that the crystallization behavior of polymers from the molten state is strongly influenced by the orientational history.…”

Section: Crystallization In Polycondensates 941mentioning

confidence: 98%

CRYSTALLIZATION IN PARTIALLY MOLTEN ORIENTED BLENDS OF POLYCONDENSATES AS REVEALED BY X-RAY STUDIES^*

Fakirov

Stribeck

Apostolov

et al. 2001

Journal of Macromolecular Science, Part B

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Oriented fibers or films of binary polymer blends from polycondensates were investigated by two-dimensional (2D) wide-angle X-ray scattering (WAXS) during the finishing process of microfibrillar reinforced composite (MFC) preparation, that is, heating to a temperature between the melting temperatures of the two components, isothermal annealing, and subsequent cooling. It is shown that the crystallization behavior in such MFC from polycondensates depends not only on the blend composition, but also on thermal treatment conditions. Poly(ethylene terephthalate)/polyamide 12 (PET/PA12), poly(butylene terephthalate)/poly(ether ester) (PBT/PEE), and PET/PA6 (polyamide 6) composites were prepared in various compositions from the components. Materials were investigated using rotating anode and synchrotron X-ray source facilities. The effect of the annealing time on the expected isotropization of the lower melting component was studied in the PET/PA6 *Dedicated to Prof. Francisco J. Baltá Calleja on the occasion of his 65th ORDER REPRINTS 936FAKIROV ET AL.blend. It was found that PA6 isotropization took place after 2 h; shorter (up to 30 min) and longer (up to 8 h) melt annealing results in oriented crystallization due to different reasons. In PET/PA12 composites, the effect of PA12 transcrystallization with reorientation was confirmed for various blend compositions. The relative strength of the effect decreases with progressing bulk crystallization. Earlier presumed coexistence of isotropic and highly oriented crystallites of the same kind with drawn PBT/PEE blend was confirmed by WAXS from a synchrotron source.

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Memory effects in polymers. I. Orientational memory in the molten state; its relationship to polymer structure and influence on recrystallization rate and morphology

Cited by 63 publications

References 2 publications

Influence of reprocessing on the mechanical properties and structure of polyamide 6

Influence of reprocessing on the mechanical properties and structure of polyamide 6

Hydrogen bonding, mobility, and structural transitions in aliphatic polyamides

CRYSTALLIZATION IN PARTIALLY MOLTEN ORIENTED BLENDS OF POLYCONDENSATES AS REVEALED BY X-RAY STUDIES^*

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Memory effects in polymers. I. Orientational memory in the molten state; its relationship to polymer structure and influence on recrystallization rate and morphology

Cited by 63 publications

References 2 publications

Influence of reprocessing on the mechanical properties and structure of polyamide 6

Influence of reprocessing on the mechanical properties and structure of polyamide 6

Hydrogen bonding, mobility, and structural transitions in aliphatic polyamides

CRYSTALLIZATION IN PARTIALLY MOLTEN ORIENTED BLENDS OF POLYCONDENSATES AS REVEALED BY X-RAY STUDIES*

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Product

Resources

About

CRYSTALLIZATION IN PARTIALLY MOLTEN ORIENTED BLENDS OF POLYCONDENSATES AS REVEALED BY X-RAY STUDIES^*