Parameters characterizing the kinetics of the non-isothermal crystallization of polyamide 5,6 determined by differential scanning calorimetry

Eltahir, Yassir A.; Saeed, Haroon A. M.; Yuejun, Chen; Xia, Yueyuan; Wang, Yimin

doi:10.1515/polyeng-2013-0250

Cited by 28 publications

(12 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The interest on the study of odd derivatives is nowadays increasing due to two main points: (a) The necessity to produce polymers from renewable resources that could substitute fossil-based materials [ 38 , 39 , 40 , 41 ]. In this sense, nylons 5 6 [ 42 , 43 , 44 , 45 ], 6 9 [ 46 ] and 13 6 [ 30 ] are gaining attention. (b) The odd numbered polyamides may display ferroelectric properties [ 47 , 48 ] and in particular the peculiar structure of nylon 6 9 has been considered to get polymers with piezoelectric activity [ 46 ].…”

Section: Introductionmentioning

confidence: 99%

Thermally Induced Structural Transitions of Nylon 4 9 as a New Example of Even–Odd Polyamides

et al. 2018

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

Thermally Induced Structural Transitions of Nylon 4 9 as a New Example of Even–Odd Polyamides

et al. 2018

View full text Add to dashboard Cite

show abstract

“…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%

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

Murase

Casas

Martínez

et al. 2015

Polymer

View full text Add to dashboard Cite

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.

show abstract

“…The value of ΔE was negative, which was due to the energy released during the transition from a molten fluid to a crystalline state. 51 The crystal activation energy of the reactive blends was smaller than that of the pure PA6, indicating that the crystallization rate increased due to the heterogeneous nucleation of the submicron-sized ABS. The addition of ABS increased the number of crystal nuclei and accelerated the nucleation rate of PA6.…”

Section: Resultsmentioning

confidence: 94%

“…The activation energy calculated from the slope is shown in Table . The value of Δ E was negative, which was due to the energy released during the transition from a molten fluid to a crystalline state . The crystal activation energy of the reactive blends was smaller than that of the pure PA6, indicating that the crystallization rate increased due to the heterogeneous nucleation of the submicron-sized ABS.…”

Section: Resultsmentioning

confidence: 96%

Rheological and Crystallization Properties of ABS/PA6-Compatibilized Blends via In Situ Reactive Extrusion

Zhao

Yan

et al. 2020

ACS Omega

View full text Add to dashboard Cite

ABS/PA6-compatibilized blends were prepared by in situ reactive extrusion method. The main objective was to evaluate the influences of the morphology and blend composition on the rheological and nonisothermal crystallization properties. The morphology of submicron-sized ABS droplets evenly dispersed in PA6 led to dilatant fluid behavior and a transition from elastic to viscous behavior in the low-frequency region. The crystallization results indicated that reactive blends had elevated crystallization temperatures and crystallization rates, which were due to the heterogeneous nucleation of the submicron-sized ABS particles. In addition, it was observed that the theory by Mo suitably described the nonisothermal crystallization process. The activation energy slightly decreased for ABS contents of 5 and 15 wt % and then increased for a content of 25 wt %, indicating that the ABS promoted the crystallization of the blends at appropriate contents.

show abstract

Parameters characterizing the kinetics of the non-isothermal crystallization of polyamide 5,6 determined by differential scanning calorimetry

Cited by 28 publications

References 25 publications

Thermally Induced Structural Transitions of Nylon 4 9 as a New Example of Even–Odd Polyamides

Thermally Induced Structural Transitions of Nylon 4 9 as a New Example of Even–Odd Polyamides

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

Rheological and Crystallization Properties of ABS/PA6-Compatibilized Blends via In Situ Reactive Extrusion

Contact Info

Product

Resources

About