The most pronounced changes upon long storage time are observed for the rigid fraction of PPR (fraction 1).
This behavior is attributed to the chemical connection between the mobile and the rigid fraction of the polymer.
12.5 h annealing at 260 °C causes a large increase in the amount of the rigid fraction in linear PA46, whereas WAXD crystallinity only slightly increases upon annealing.
1H NMR transverse magnetization relaxation (T2 relaxation) experiments show that, at temperatures well above Tg, the amount of low mobile chain segments (rigid fraction) in all injection-molded samples equals 60 63%.
The increase in the rigid fraction is largely caused by immobilization of the amorphous phase due to chains rearrangements resulting in stronger hydrogen bonds between amide groups in the amorphous phase.
To model these systems we assume that the interlamellar 'amorphous' or non-crystalline species do not contribute to the glass transition and use the SAXS parameters to calculate a total rigid fraction.
Four different phases are analysed with this method: (1) crystalline phase and rigid fraction of the amorphous phase, (2) semi-rigid crystal-amorphous interface, (3) soft fraction of the amorphous phase and (4) rubbery-like material.
The amount of the rigid fraction in annealed samples is smaller in samples with higher amount of branches, and molecular mobility in the rigid and soft fractions is larger.
