Tensile Deformation of Bulk Polyamide 6 in the Preyield Strain Range. Micro-Macro Strain Relationships via in Situ SAXS and WAXS

cited By 4International audienceThe macroscopic tensile deformation behavior of bulk PA6 was investigated in the elastic strain range. Samples having predominant α and β crystal structures were prepared thanks to appropriate crystallization procedures. Both materials were studied above and below the glass transition temperature of the amorphous phase. In parallel, the microscopic deformation behavior of these samples was followed up by combined in situ wide-angle and small-angle X-ray scattering. The change of SAXS long period over the whole azimuthal distribution was used to assess the local deformation at the scale of the lamella stacks in all directions. The WAXS patterns were used to assess the local crystal strains. Local stresses were further computed thanks to the elastic constant borrowed from the literature. The whole set of data allowed to establish micro-macro strain correlations and to determine the local elastic properties in the crystalline and amorphous phases. The effective tensile modulus of the amorphous phase of PA6 within lamella stacks at 120 °C is found to be several orders of magnitude higher than that of bulk amorphous PA6 in the rubbery state, i.e., close to that of the glassy state. This gives evidence of a strong confinement or strong Poisson’s effect of the amorphous layers due to the form factor to the stiff crystalline lamellae. © 2017 American Chemical Society