Melting and Transformation Behavior of γ Form Nylon 6 under High Pressure

Hiramatsu, Nobuyasu; Hirakawa, Susumu

doi:10.1295/polymj.14.165

Cited by 51 publications

(36 citation statements)

References 16 publications

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“…Here, as a prerequisite the interaction between polymer and organic modifier should be favorable. PA6 has two crystal forms: thermodynamically stable α-form (melting temperature, ∼ 217 • C) consisting of fully extended planar zigzag chains, in which adjacent antiparallel chains are jointed to each other by hydrogen bond 13 and the γ-form (melting temperature, ∼ 210 • C) composed of pleated sheets of parallel chains jointed by hydrogen bonds. 13,14 The silicate surface in PA6/organosilicate nanocomposite induces conformational changes of the polymer chains due to restriction of chain mobility near the surface.…”

Section: Resultsmentioning

confidence: 99%

Effects of Shear on Melt Exfoliation of Clay in Preparation of Nylon 6/Organoclay Nanocomposites

Kim

et al. 2002

Polym J

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ABSTRACT:The effect of shear stress on the exfoliation of organosilicate layers in the polyamide 6 (PA6) matrix was investigated using an X-Ray diffractometer (XRD). Shear stress was controlled by changing the molecular weight of PA6, mixing temperature, and rotor speed of a mini-molder. When Cloisite R 30 B (30 B), which favorably interacts with PA6, was used as organosilicate, silicate layers were exfoliated even at zero shear stress when annealing time was long enough. When shear stress was applied, the exfoliation of clay took place in a much shorter time compared to the statically annealed sample, and was dependent on molecular weight of matrix and mixing temperature. For poorly interacting PA6/ Cloisite R 25 A nanocomposites, only well ordered intercalated ones were obtained under high shear conditions. Shear stress applied during mixing thus plays a secondary role. Breaking silicate agglomerates into primary particles facilitates polymer chains to diffuse easily into the gallery of layered silicates, and thus enhances the degree of exfoliation at a given mixing condition. Thermodynamics, especially the diffusion of polymer chain into the silicate layers, plays primary roles in preparing the nanocomposites with exfoliated structure.KEY WORDS Silicate / Polyamde 6 / Nanocomposite / Shear / Intercalation / Exfoliation / Polymer/layered silicate nanocomposites have recently received considerable attention as an effective way to overcome the shortcomings of conventional mineral-filled nanocomposites. 1, 2 When silicate layers are exfoliated and randomly distributed in polymer matrix, the nanocomposites exhibit improved mechanical, thermal, and barrier properties even at a loading level of 5 wt%.To make exfoliated nanocomposites, the meltcompounding method is especially attractive because current polymer processing techniques can be applied with minimal modification. The method allows us to prepare directly nanocomposites using conventional compounding devices such as extruders used for commercial polymers. There are many factors to be considered for preparing nanocomposites with exfoliated silicate layers using the method. First, interactions between polymer and silicate should be controlled for polymer chains to diffuse into silicate layers by reducing strong electrostatic force between silicate layers. This may be achieved by modifying hydrophilic silicate with an organic modifier, which favorably interacts with hydrophobic polymer. Some aspects on polymer/organosilicate nanocomposites, prepared by melt processing, have been investigated in recent years: interlayer structure of modified silicates, 3 structural evolution during polymer melt intercalation, 4 mobility of intercalated polymer chains described by glass transition behavior, 5 and kinetics of polymer intercalation. 6 The effect of the chemical structure of organic modifier such as the length and number of alkyl groups and the polarity of polymers on the intercalation behavior has been investigated. 7 More recently, we reported that polymers could b...

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Section: Resultsmentioning

confidence: 99%

Effects of Shear on Melt Exfoliation of Clay in Preparation of Nylon 6/Organoclay Nanocomposites

Kim

et al. 2002

Polym J

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“…The transformation from c to a can be brought about by heat, strain, or solvents (water) either alone or in combination. 12,18,20,[25][26][27][28] The c form obtained by melt casting, spinning, drawing, and in some instance with nanoclays transforms into a before melting and is most likely a solid-state reorganization. However, the c form obtained by nucleation with nanoclays or by iodine treatments remains c up to melting.…”

Section: Structure Crystalline Structurementioning

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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“…In almost all cases mixtures of a-like and g-like phases of different order are found, strongly depending on the crystallization conditions, such as the crystallization temperature, cooling rate [14,19,21,[33][34][35][36][37], shear rate [22,26,29,31,[38][39][40], humidity [22,35,41] and pressure [40].…”

Section: Introductionmentioning

confidence: 99%