Structural transitions of nylon 47 and clay influence on its crystallization behavior

Morales-Gámez, Laura; Casas, María Teresa; Franco, Lourdes; Puiggalı́, Jordi

doi:10.1016/j.eurpolymj.2013.02.030

Cited by 15 publications

(31 citation statements)

References 30 publications

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“…However, bonds formed along the two unit cell diagonals were equivalent and stronger [20]. Figure 2a) where a form I to form II transition is described 9 between 60 and 120 ºC [19]. In this case, the intensity of the two equatorial reflections at 0.430 and 0.389 nm gradually diminished during heating while new reflections with increasing intensity appeared near 0.422 and 0.407 nm.…”

Section: Time Resolved Waxd Data On Heating and Cooling Processes: Brmentioning

confidence: 93%

“…More complex geometries have been postulated for the room temperature structures of polyamides containing glycine units [14] and also of several odd-even and even-odd 4 nylons [8,[15][16][17][18][19][20][21][22][23][24][25][26]. These structures were characterized by the establishment of hydrogen bonds along three and two directions as a consequence of the conformational preferences of glycine residues and the inability to establish a saturated intrasheet hydrogen bonding scheme when an all-trans molecular conformation was assumed and odd diamine or diacid units were involved (Figure 1a).…”

Section: Introductionmentioning

confidence: 99%

“…Properties of spherulites of even-odd nylons have been less studied, but pioneering and phenomenological works of Magill [39] performed with nylons 4 9, 6 7 and 6 9, and more recently results reported for nylon 4 7 indicate a peculiar behavior [19]. Thus, a reversible change in birefringence induced by temperature was detected.…”

Section: Introductionmentioning

confidence: 99%

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Reversible changes induced by temperature in the spherulitic birefringence of nylon 6 9

Murase

Casas

Martínez

et al. 2015

Polymer

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Spherulitic morphologies of nylon 6 9 as an example of an even-odd nylon were studied by optical microscopy. A well-defined dependence on crystallization temperature was found. In particular, positively birefringent spherulites were characteristic for temperatures higher than 232 ºC, low birefringence spherulites developed between 232 and 225 ºC, positive ringed spherulites were found between 225 and 220 ºC, and finally negative fibrillar spherulites were formed at temperatures lower than 220 ºC. These optical properties were clearly different from those observed with even-even nylons (e.g., negative and positive birefringence for high and low temperatures, respectively), and may derive from the peculiar crystalline structures determined for even-odd nylons.Furthermore, low birefringence spherulites were characterized by a flat-on lamellar disposition and reversibility of the birefringence sign in the 80-120 ºC temperature interval (positive and negative values at high and low temperatures, respectively).Real time WAXD profiles taken during heating and cooling processes demonstrated that different crystalline structures (named I, II and III) developed depending on the temperature and crystallization procedure of samples (e.g., from solution or from the melt state). Crystalline structures were characterized by the formation of hydrogen bonds along two crystalline directions in all cases, a peculiar arrangement that may account for the development of positive and negative spherulites in a more simple way than formulated for conventional polyamides having a single hydrogen bonding direction. DSC and FTIR data also showed a complex structural behavior with structural transitions in the 80-120 ºC range, a region that corresponds to birefringence sign reversibility.

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Section: Time Resolved Waxd Data On Heating and Cooling Processes: Brmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Reversible changes induced by temperature in the spherulitic birefringence of nylon 6 9

Murase

Casas

Martínez

et al. 2015

Polymer

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“…Nevertheless, X‐ray diffraction patterns of solution crystallized samples usually showed the typical strong reflections of conventional nylons (e.g., those appearing at spacings close to 0.440 and 0.380 nm). This feature has been described for both odd‐even nylons, such as 5 6, 5 10, 9 2, 11 10, 11 12, and 13 6, and even‐odd nylons like 6 5, 12 5, 6 13, 4 7, and 6 9 . Therefore, a new structure based on a molecular chain conformation that causes a slight rotation of consecutive amide groups of the odd diamide unit was proposed.…”

Section: Introductionmentioning

confidence: 91%

“…However, a new intermediate structure close to a pseudohexagonal form (named as form II) could also be observed in some cases. Thus, nylons 4 7 and 6 9 gave predominantly rise to form II when crystallized from the melt state, but a partial transition towards form I could be detected at low temperature (e.g., 80–100 °C). On the contrary, solution crystallized samples showed a well differentiated behavior on heating.…”

Section: Introductionmentioning

confidence: 96%

Temperature‐induced structural changes in even‐odd nylons with long polymethylene segments

Olmo

Rota

Martínez

et al. 2016

J Polym Sci B Polym Phys

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Structural transitions of nylons 8 9 and 12 9 during heating and cooling processes were investigated using calorimetric, spectroscopic and real time X-ray diffraction data.These even-odd nylons had three polymorphic forms related to structures where hydrogen bonds were established in two planar directions. Heating processes showed a first structural transition at low temperature where the two strong reflections related to the packing mode of the low temperature structure (form I) disappeared instead of moving together and merging into a single reflection, as observed for conventional even-even nylons. The high temperature structure corresponded to a typical pseudohexagonal packing (form III) attained after the named Brill transition temperature. Structural transitions were not completely reversible since an intermediate structure (form II) became clearly predominant at room temperature in subsequent cooling processes.A single spherulitic morphology with negative birefringence and a flat-on edge-on lamellar disposition was obtained when the two studied polyamides crystallized from the melt state. Kinetic analyses indicated that both nylons crystallized according to a single regime and a thermal nucleation. Results also pointed out a secondary nucleation constant for nylon 12 9 higher than that for nylon 8 9, suggesting greater difficulty in crystallizing when the amide content decreased.

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Aliphatic polyamides (nylons): Interplay between hydrogen bonds and crystalline structures, polymorphic transitions and crystallization

Puiggalı́

2021

Polymer Crystallization

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Aliphatic polyamides (nylons) constitute a family of polymers with outstanding properties and multiple applications. Despite the intensive research studies carried out with nylons, there are still multiple unsolved questions concerning crystallization processes, crystalline structures, polymorphic transitions, and crystalline morphologies. Constrains imposed by the strong intermolecular interactions affect the amorphous state, the rigid amorphous phase, the molecular folding, the morphology and obviously the crystalline structure. Some of these relevant points are discussed in the present work.

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Structural transitions of nylon 47 and clay influence on its crystallization behavior

Cited by 15 publications

References 30 publications

Reversible changes induced by temperature in the spherulitic birefringence of nylon 6 9

Reversible changes induced by temperature in the spherulitic birefringence of nylon 6 9

Temperature‐induced structural changes in even‐odd nylons with long polymethylene segments

Aliphatic polyamides (nylons): Interplay between hydrogen bonds and crystalline structures, polymorphic transitions and crystallization

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