Crystalline structure of polyamide 12 as revealed by solid‐state ¹³C NMR and synchrotron WAXS and SAXS

Abstract

The crystalline structure of polyamide‐12 (PA12) was studied by solid‐state 13C nuclear magnetic resonance (NMR) as well as by synchrotron wide‐ and small‐angle X‐ray scattering (WAXS and SAXS). Isotropic and oriented PA12 showed different NMR spectra ascribed to γ‐ and γ′‐crystalline modifications, respectively. On the basis of the position of the first diffraction peak, the isotropic γ‐form and the oriented γ′‐form were shown to be with hexagonal crystalline lattice at room temperature. When heated, the two PA12 polymorphs demonstrated different behaviors. Above 140 °C, the isotropic γ‐PA12 partially transformed into α‐modification. No such transition was observed with the oriented γ′‐PA12 phase even after annealing at temperatures close to melting. A γ′–γ transition was observed here only after isotropization by melting point. Various structural parameters were extracted from the WAXS and SAXS patterns and analyzed as a function of temperature and orientation: the degree of crystallinity, the d‐spacings, the Bragg's long spacings, the average thicknesses of the crystalline (lc) and amorphous (la) phases, and the linear crystallinity xcl within the lamellar stacks. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 3720–3733, 2005

Polyamide‐12/Functionalized Carbon Nanofiber Composites: Evaluation of Thermal and Mechanical Properties

“…The presence of a double melting endothermic peak may be related to melting‐recrystallization processes or may be due to mixed crystal structures. The last hypothesis seems to be unlikely, since polyamide‐12 shows little tendency toward polymorphism and crystallizes mostly in the γ‐phase 45–48…”

Polyamide/Carbon Nanoparticles Nanocomposites: A Review

“…As it is seen in Fig. , there are two polymorphic phases of Polyamide 12 (PA12), namely the α and the γ phase, the more stable one being the γ form .…”

Water sorption of PA12/PA6/MWCNT composites with a segregated conductive network: structure–property relationships

“…The diffraction peaks at 2h = 20.6°a nd 23.4°are assigned to (200) and (202) ? (002) planes of the a crystalline phase, whereas the peaks at 21.6°are assigned to (200) and (001) planes of the c phase [19,32] for PA6 and at 21.7°to the (200) plane of the c phase in the case of PA12 [33]. To estimate the sample crystallinity, a deconvolution procedure was applied on the patterns using the open-source software Fityk [34].…”