Induced γ → α Crystal Transformation in Blends of Polyamide 6 and Liquid Crystalline Copolyester

Abstract

The equilibrium melting temperatures and the induced γ → α crystal transformation in blends of random liquid crystalline copoly(oxybenzoate−ethylene terephthalate) at molar ratio 60/40 (P64) and polyamide 6 (PA6) under different thermal treatments were investigated with differential scanning calorimetry and wide-angle X-ray diffraction, respectively. It was found that the equilibrium melting temperatures of P64/PA6 blends depended strongly on the amount of P64, and the presence of a small amount of P64 in PA6, around 5%, induced additional crystallization of the α-form crystal in the quenched PA6. Moreover, the onset temperature for the γ → α crystal transformation in the 5/95 P64/PA6 blend was reduced by 30 °C as compared to that in the pure PA6 case (160 °C vs 130 °C).

Bio-polyamides based on renewable raw materials

“…39°. Moreover, the reflections at *21°can be assigned as cphase reflections, formed during quenching from the melt state [35,41]. The smectic phase found around 20°was also reported for PA 11 using the temperature-dependent X-ray measurements [42,43].…”

“…On the contrary, for PA 6.6, Liu and coworkers assign this reflection as one of the distinctive features of the a-phase in polyamides and state that polyamides present usually more stable a-phase rather than c ones in XRD [20]. In the c-form phase of the polyamide, hydrogen bonds take position between parallel macrochains, while in a-form the antiparallel arrangement is present, and the latter is more stable because of shorter hydrogen bonds [35].…”

“…3) differs in the region of 2h of 21°-25°, and this suggests that only the a-crystalline form is present. However, it is known that the polymorphic structures in polyamides come from different spatial arrangement in the hydrogen bondings; thus, this may be also related to the less perfect crystalline structure of PA 6.10 [35]. On the other hand, FTIR spectra for PA 6.10 show an extra ''amorphous'' small peak (at 877 cm -1 ) and a new ''crystalline'' one (at 1179 cm -1 ), while the other ''crystalline'' markers were diminished.…”

Investigation on Unusual Crystallization Behavior in Polyamide 6/Montmorillonite Nanocomposites

“…Besides, the weak diffraction peak at 2h = 11.0 8 is another feature of the c-crystalline form. [29,30] The polymorphic structures of PA6 result from different spatial arrangement in the hydrogen bonding between the oxygen in the carbonyl group of one chain and the hydrogen attached to the nitrogen in the neighboring chain. The c-crystalline form is constituted by PA6 molecules adopting hydrogen bonding in parallel chainarrangement, whereas hydrogen bonding in antiparallel chain-arrangement is characteristic of the a-form.…”

Conducting nanocomposites based on polyamide 6,6 and carbon nanofibers prepared by cryogenic grinding

“…The patterns can be deconvoluted into a broad amorphous halo and three sharper peaks originated by the diffracting planes of the crystalline regions. All samples exhibit the two main peaks corresponding to the a crystalline form of PA66 [6] located at 20.3°and 23.6°. Additionally, the diffractograms exhibit a peak at 26.2°corresponding to the reflection from the graphitic layer structure of the CNF.…”