Thermally induced structural transitions of nylon 4 9 as a new example of even-odd polyamides
Olmo, Cristian (Universitat Politècnica de Catalunya)
Casas, Maria Teresa (Universitat Politècnica de Catalunya)
Martínez, Juan Carlos (ALBA Laboratori de Llum de Sincrotró)
Franco García, María Lourdes (Universitat Politècnica de Catalunya)
Puiggalí, Jordi (Universitat Politècnica de Catalunya)

Fecha:	2018
Resumen:	Crystalline morphology and structure of nylon 4 9 have been studied by means of optical and transmission electron microscopies, and X-ray diffraction. Rhombic crystals were characteristic of crystallization from glycerin dilute solutions, although the final morphology was dependent on the crystallization temperature. In any case, a single electron diffraction pattern was always obtained, being characteristic a 2 mm symmetry and reflections at spacings that were indicative of a projected rectangular unit cell with hydrogen bonds established along two planar directions (i. e. , the diagonals of the unit cell), as it was determined from related polyamides. Crystallization from the melt gave rise to negative birefringent spherulites with a morphology (axialitic, speckled or ringed) that was dependent on the crystallization temperature. Kinetic analysis indicated that melt crystallization took place according to two growth mechanisms (Regimes II and III), which reflect distinct secondary nucleation rates. A complex polymorphic behavior on heating and cooling processes was evidenced by real time synchrotron experiments, being determined an intermediate crystalline structure as well as the typical pseudohexagonal arrangement associated to the Brill transition. Polymorphic transitions were highly dependent on the initial crystalline structure, being enhanced the structural transition from the low temperature structure to the intermediate one when traces of the latter were initially present. Calorimetric and infrared studies supported also the detected thermal transitions of nylon 4 9.
Ayudas:	Ministerio de Economía y Competitividad MAT2015-69547-R Agència de Gestió d'Ajuts Universitaris i de Recerca 2014/SGR-188
Derechos:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Lengua:	Anglès
Documento:	Article ; recerca ; Versió publicada
Materia:	Crystalline structure ; Hydrogen bonds ; Lamellar morphology ; Polyamides ; Spherulites ; Synchrotron radiation ; Thermal transitions
Publicado en:	Polymers, Vol. 10, Issue 2 (February 2018) , art. 198, ISSN 2073-4360

DOI: 10.3390/polym10020198
PMID: 30966234

24 p, 7.0 MB

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