Premelting crystalline relaxations and phase transitions in nylon 6 and 6,6

Murthy, N. Sanjeeva; Curran, Sean A.; Aharoni, Shaul M.; Minor, H.

doi:10.1021/ma00011a027

Cited by 243 publications

(236 citation statements)

References 7 publications

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“…17 It is most likely that phases other than a and c correspond to structures in which the hydrogen bonds form a 2D network, the extreme situation being the pseudohexagonal phase that persists at room temperature. 18,19 a 0 is the high-temperature phase of a, 20,21 and b is the disordered a phase. 15,19,22,23 A k phase is observed in PA-6 oligomers.…”

Section: Structure Crystalline Structurementioning

confidence: 99%

“…Similar a-like phases have been reported above the Brill transition temperature (T B ). 20,21 Hydrogen Bonding Nearly all the amide groups that separate a sequence of methylene groups in nylons are hydrogen-bonded. 31,32 Hydrogen-bonded sheets are similar to basal carbon planes in the carbon structure.…”

Section: Structure Crystalline Structurementioning

confidence: 99%

“…98,99 In PA-6, the replacement of the initial pair of peaks by a different pair is identified as the transformation from the room-temperature a phase to the high-temperature a 0 phase. 20,21 If the defining criterion for a Brill transition is the merging of two peaks, then the premelting transformation in PA-6 and PA-12 is not a Brill transition. On the other hand, if the criterion is the onset of a new relaxation process, large-amplitude librational motion of the methylene segments pinned by the amide groups in the crystal, then the premelting-phase crystalline-phase transition of PA-6 and PA-12 and possibly other nylons is also a Brill transition.…”

Section: Premelting Transitionsmentioning

confidence: 99%

“…97 The crystallization temperature, orientation, residual stresses, and solvents also influence this transition. 20,21,[103][104][105] Chain Mobility…”

Section: Premelting Transitionsmentioning

confidence: 99%

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Hydrogen bonding, mobility, and structural transitions in aliphatic polyamides

Murthy

2006

J Polym Sci B Polym Phys

206

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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Section: Structure Crystalline Structurementioning

confidence: 99%

Section: Structure Crystalline Structurementioning

confidence: 99%

Section: Premelting Transitionsmentioning

confidence: 99%

“…97 The crystallization temperature, orientation, residual stresses, and solvents also influence this transition. 20,21,[103][104][105] Chain Mobility…”

Section: Premelting Transitionsmentioning

confidence: 99%

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Hydrogen bonding, mobility, and structural transitions in aliphatic polyamides

Murthy

2006

J Polym Sci B Polym Phys

206

197

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“…Figure 7 compares the crystal structures of PA66 and nanocomposites from XRD curves done at room tempera- ture. Figure 7 shows that there are two strong peaks for pure PA66, with a spacing of 0.44 nm at 2y ¼ 23.68 and of 0.37 nm at 2y ¼ 27.88, which corresponds to crystalline form a 1 and a 2 [30], respectively. Upon addition of clay, either at 2% loading (Fig.…”

Section: Xrd Analysismentioning

confidence: 99%

Nylon 66/clay nanocomposite structure development in a twin screw extruder

Lin

Thümen

Heim

et al. 2009

Polymer Engineering & Sci

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Nylon 66/clay nanocomposites were prepared in a Berstorff ZE25A UTX Ultra-glide corotating twin screw extruder at 2708C. Two types of extruder configurations with different mixing sections were used. One comprised two kneading block sections in the screws (KB only) and the other had a combination of a multiprocess-element (MPE) section and a kneading block section. Samples at eight different locations along the extruder screw were obtained and analyzed using scanning electron microscope and transmission electron microscope to examine the morphology development of clay inside nylon down the length of the extruder. It is found that the clay aggregates are quickly broken into smaller tactoids (micron size) and then even much smaller clay bundles (nanometer size) and single clay platelets in the first mixing section. The structure changes in the second mixing section are much less significant. X-ray diffraction (XRD) analysis of the nanocomposite products showed small, or disappearance of, characteristic XRD (001) peaks, which indicates partial exfoliation, or complete exfoliation,

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