Effects of annealing (solid and melt) on the time evolution of polymorphic structure of PA6/silicate nanocomposites

The effects of annealing including solid-state annealing (190 degreesC) and melt-state annealing (230 and 250 degreesC) on the polymorphic behavior and thermal property of polyamide 6 (PA6)/layered-silicate nanocomposites (PA6LSN) have been investigated as a function of annealing time using Modulated Differential Scanning Calorimetry (MDSC) and wide angle X-ray diffraction. For comparison, thermal behavior and polymorphism of pure PA6 were also studied. It was demonstrated that PA6LSN and PA6 exhibited a similar polymorphic behavior when they were annealed in the solid state for different time duration. As the annealing temperature was elevated to 230 and 250 degreesC, significant differences in thermal behavior and polymorphism between PA6LSN and PA6 could be found. For example, the gamma phase became the absolutely dominating for PA6LSN. while the a crystal was the most predominant phase in neat PA6. Moreover, a new endothermic peak is observed around 235 degreesC in all PA6LSN MDSC scans, which might be related to the melting of PA6 lamellae formed in the confined environment on the surface of the nano-silicate. (C) 2004 Elsevier Ltd. All rights reserved.