Structural transitions of nylon 47 and clay influence on its crystallization behavior

Abstract

Basic diffraction data on nylon 47 pointed out a peculiar structure of hydrogen bonds along two directions. Nylon 47 showed reversible polymorphic transitions during heating/cooling processes that were analyzed by real time synchrotron WAXD experiments. Results indicated that nylon 47 had a first structural transition at low temperature, followed by a gradual Brill transition towards a pseudohexagonal packing. Nylon 47 crystallized from the melt giving rise to spherulites with different characteristics than those attained with conventional even-even nylons. Interestingly, spherulites crystallized at low supercooling underwent a reversible change in birefringence with temperature. This was due to the reversible structural changes caused by temperature variations and the flat on lamellar morphology. Intercalated and exfoliated nanocomposites based on nylon 47 were prepared by solution intercalation and melt mixing using Cloisites 25A and 30B. The influence of the final silicate layer morphology on the hot crystallization behavior was investigated. Crystallization rates of the neat polymer and its two nanocomposites were significantly different, mainly due to variations in the primary nucleation