Melt memory effects on recrystallization of polyamide 6 revealed by depolarized light scattering and small‐angle X‐ray scattering

Abstract

Melt memory effects on recrystallization of polyamide 6 were studied in a length scale from nm to lm using small-angle X-ray scattering (SAXS) and depolarized light scattering (DPLS). The memory effects on recrystallization rate were discussed in terms of the incubation period before nucleation and the half time of the crystallization, which were measures of the nucleation rate and the growth rate, respectively. Both rates are almost independent of the annealing temperature of the melt in the remelting process for the short term annealing below $ 3 min while they are slowed as the annealing temperature increases for the long term annealing, showing that the relaxation of melt mem-ory takes very long even above the equilibrium melting temperature T 0 m . Extrapolating the incubation period to infinite annealing, time we found that it was very hard to attain the fully relaxed state in polyamide 6 even above the equilibrium melting temperature. This must be due to the strong hydrogen bonding in polyamide 6. We also discuss the memory effects on the final structure after recrystallization based on the SAXS and DPLS profiles.

Self-Nucleation of Crystalline Phases Within Homopolymers, Polymer Blends, Copolymers, and Nanocomposites

“…In other words, L-PCL samples have a much higher crystalline memory than CPCLs of similar molecular lengths. Crystalline memory effects are a function of entanglement density [26,40,44,63,[122][123][124][125][126], and the entanglement density in LPCLs is significantly higher than in C-PCL as a result of its free chain ends. Therefore, partially disentangled PCL cyclic chains can reach a random coil conformation, or a uniform melt, faster than more entangled linear chains.…”

Overview and critical survey of polyamide6 structural habits: Misconceptions and controversies

“…Another specific phenomenon of polyamides resulting from the presence of H-bonds in the molten state is the so-called memory effect upon crystallization. [31,[157][158][159][160][161] Though H-bonds are not as strong in the molten state as in the solid state, [105] their persistence in the melt is responsible for remnants of organized domains far above the melting point. As originally pointed out by Illers [47] this kind of molten crystals survivors behave as homogeneous crystal nuclei upon cooling and promote early crystallization.…”

Aliphatic polyamides (nylons): Interplay between hydrogen bonds and crystalline structures, polymorphic transitions and crystallization

“…Another specific phenomenon of polyamides resulting from the presence of H‐bonds in the molten state is the so called memory effect upon crystallization 6–9 . Hydrogen bonds are weaker in the molten state, but some organized domains may persist 10 .…”