Memory effects in polymers. III. Processing history vs. crystallization rate of nylon 6—comments on the origin of memory effect

Abstract

AbstractOur previous publication on this subject has dealt with the processing history effects on the crystallization rate of nylon 6 from the molten state. In this manuscript we present some insights into the molecular origin of the observed effects. Based on the available experimental data, we hypothesize that melt‐extrusion, solution precipitation, or freeze grinding of virgin nylon 6 lead to a more ordered molecular arrangement. This enhanced order persists in the molten state due to H‐bonding and causes a faster crystallization. The virgin material, however, due to its process history, e.g. polycondensation in a viscous melt, is disordered and stays disordered even in the molten state due to H‐bonding. Processing treatments such as melt‐extrusion or freeze‐grinding (high shear stresses) or solution precipitation are required to overcome the H‐bond stabilized disordered environment in virgin nylon 6 and introduce locally ordered regions (nucleation sites), thus accounting for an increase in the crystallization rate.