Deutsche Tagung f ¨ur Forschung mit ... - SNI-Portal

Weiche Materie Poster: Do., 13:00–15:30 D-P326
Relationship between Crystalline Structure and Mechanical Behavior in
Isotropic and Oriented Polyamide 6
Nadya Dencheva 1 , Zlatan Denchev 1 , Maria Jovita Oliveira 1 , Sérgio S.
Funari 2
1 IPC Institute for Polymers and Composites, Department of Polymer Engineering,
University of Minho, 4800-058 Guimarães, Portugal – 2 HASYLAB at DESY,
Notkestrase 85, 22603 Hamburg, Germany
The present study discusses the mutual relationship between the crystalline structure
and the mechanical behavior in polyamide 6 (PA6) isotropic films and oriented cables
prepared by compression molding or by consecutive extrusion and cold drawing.
These samples were afterwards isothermally annealed in the 120-200 o C range and than
subjected to tensile tests at room temperature. 2D synchrotron WAXS and SAXS
patterns were obtained before and after mechanical failure. The structural data obtained
from these patterns (e.g., degree of crystallinity, d-spacing and long spacing
values, orientation, content of α- and γ-PA6 polymorphs) were discussed in relation
with the mechanical properties (e.g., Young modulus, yield stress and break strain) of
the corresponding isotropic and oriented samples.
It was demonstrated that annealing of isotropic PA6 in the 120-200 o C range results in
an increase in both Young modulus (from 730 to 1030 MPa) and of the yield stress values
- from 40 to 50 MPa. These two findings were related to the proportional reduction
of the d-spacing of the (002) plane for α-PA6 and of the (200) plane for the γ-PA6. The
decrease of break strain values from 81 to 37 % as a function of annealing temperature
was elucidated by analysing the corresponding 2D SAXS and WAXS patterns after
mechanical failure. Stretching of samples annealed at 120 o C resulted in extension of
the amorphous domains whereas the crystalline ones did not orient. Samples annealed
at 160 and 200 o C showed significant anisotropy of the crystalline domains along the
draw direction meaning that the amorphous phase did not absorb but transferred the
stress to the crystalline phase.
With the oriented PA6 samples, increasing the annealing temperature resulted in an
increase of Young modulus from 990 to 3800 MPa, and of the yield stress in the
135-200 MPa range, the strain decreasing from 150 to