Crystallinity and polymorphism of 6‐polyamide

Gurato, Giorgio; Fichera, Annamaria; Grandi, F. Zilio; Zannetti, Roberto; Canal, Pietro

doi:10.1002/macp.1974.021750322

Cited by 130 publications

(62 citation statements)

References 14 publications

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“…It is connected with the looser packing of PA6 chains in part of the crystalline regions of the sample PA6 LN containing more γ-crystalline form than the sample PA6 H 2 O. Specific volume of amorphous zones in polyamide 6 depends on the ratio of the α-form to the γ-form content [21]. Higher content of γ-form results in higher specific volume of the amorphous zones.…”

Section: Results Of Positron Annihilation Lifetime Spectra Measurementsmentioning

confidence: 99%

Influence of Polymer Crystallinity and Morphology on Positron Annihilation Characteristics

Dębowska

2006

Acta Phys. Pol. A

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Some most representative results for semicrystalline polymers by positron annihilation spectroscopy method, showing the influence of crystallinity and morphology of samples on positron annihilation characteristics, are reminded. The latest finding of the author's experiment on modified polyamide 6 is presented. The latter reveals that the interfacial zone between a lamella and an amorphous region may influence the ortho-positronium characteristics. The role of chain defects is stressed.

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Section: Results Of Positron Annihilation Lifetime Spectra Measurementsmentioning

confidence: 99%

Influence of Polymer Crystallinity and Morphology on Positron Annihilation Characteristics

Dębowska

2006

Acta Phys. Pol. A

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“…These changes begin to occur at 160-190 8C in PA-6. 78,85,[87][88][89][90][91] This could be due to crystalline chain relaxation that also accounts for premelting structural transitions, 87 the Brill transition being the most widely known among these. …”

Section: Temperature Effectsmentioning

confidence: 99%

Hydrogen bonding, mobility, and structural transitions in aliphatic polyamides

Murthy

2006

J Polym Sci B Polym Phys

215

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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“…The area of each peak was calculated, the crystallinity, and the proportions of each crystal form could be estimated. 22,23 The deconvolution of the XRD curve is shown in Figure 1.…”

Section: Measurements and Characterizationsmentioning

confidence: 99%

Structure and Performance of Polyamide 6/Halloysite Nanotubes Nanocomposites

et al. 2009

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Halloysite nanotubes (HNTs) are chemically modified via silylation with 3-(trimethoxysilyl)propyl methacrylate. The modified HNTs (m-HNTs) are characterized by diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, solid state 13 C NMR spectroscopy, thermogravimetric analysis (TGA) and extraction experiment. It is showed that the silane has been effectively grafted onto HNTs surface and renders the hydrophobicity to m-HNTs. The nanocomposites consisting of polyamide 6 (PA6) and m-HNTs show significantly improved mechanical properties and heat distortion temperature, which are attributed to the covalent interfacial bonding and the excellent dispersion state of m-HNTs. M-HNTs are found to disperse individually into PA6 matrix. The nucleation effect by m-HNTs is verified by the lowered fold-surface free energy of PA6/ HNTs nanocomposites and the observation of polarized optical microscopy (POM). Both high cooling rate and high m-HNTs loading are beneficial to the formation of gamma-crystals of PA6. The polymorphism could be correlated to the heterogeneous nucleation effects of m-HNTs and the interfacial interactions between m-HNTs and PA6 matrix.KEY WORDS: Polyamide / Halloysite / Nanocomposite / Mechanical Property / Crystallization / Polyamide 6 (PA6) with high fatigue strength, low friction coefficient and high resistance to a wide spectrum of fuels, oils, and chemicals, is an important semicrystalline engineering plastics and finds its applications in automobiles, electrical appliances, construction materials, transportation materials and so on. However, the drawbacks such as limited mechanical strength and dimensional stability restrict its applications. 1Since the first introduction of PA6/clay nanocomposites in 1993, 2,3 they have drawn much attention due to their unprecedented performance compared with their microcomposite counterparts. The PA6 nanocomposites with inclusions of organic montmorillonite (O-MMT), 4-6 carbon nanotubes (CNTs) 7-9 and attapulgite 10,11 have been intensively investigated.Halloysite nanotubes (HNTs) are a type of natural tubular nanoclay 12-16 and have been recognized as the effective nanosized reinforcement of polymers for better mechanical properties and thermal properties. [17][18][19][20] In the previous study, we have showed the reinforcing effects of the prinstine HNTs towords PA6. 21 In the present work, we attempt to further improve the dispersion of HNTs and the interaction between HNTs and PA6 chains through the surface treatment of HNTs by silane of 3-(trimethoxysilyl)propyl methacrylate. The mechanical properties and heat distortion temperatures of the resulted nanocomposites are presented. The kinetic parameters regarding the chain folding activation energy during the nonisothermal crystallization are calculated. The polymorphism of the nanocomposites, which is dependent of the cooling rate of the melt and HNTs loading, is revealed. The performances such as mechanical properties, heat distortion temperature and polymorphism are correlated to the heterogen...

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Crystallinity and polymorphism of 6‐polyamide

Cited by 130 publications

References 14 publications

Influence of Polymer Crystallinity and Morphology on Positron Annihilation Characteristics

Influence of Polymer Crystallinity and Morphology on Positron Annihilation Characteristics

Hydrogen bonding, mobility, and structural transitions in aliphatic polyamides

Structure and Performance of Polyamide 6/Halloysite Nanotubes Nanocomposites

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