Polymorphism in nylon 6/clay nanocomposites

X-ray diffraction methods and DSC thermal analysis have been used to investigate the structural change of nylon 6/clay nanocomposites. Nylon 6/clay has been prepared by the intercalation of ε-caprolactam and then exfoliating the layered synthetic saponite by subsequent polymerization. Both X-ray diffraction data and DSC results indicate the presence of polymorphism in nylon 6 as well as in nylon 6/clay nanocomposites. This polymorphic behavior is dependent on the cooling rate of nylon 6/clay nanocomposites from the melt and on the content of synthetic saponite in nylon 6/clay nanocomposites. The quenching from the melt induces the crystallization into the γ crystalline form. The addition of synthetic saponite may increase the crystallization rate of the α crystalline form at lower synthetic saponite content and promote the heterophase nucleation of γ crystalline form at higher synthetic saponite content. The effect of thermal annealing on the crystalline structure of nylon 6/clay nanocomposites in the range between Tg and Tm is also discussed.