Crystallization behaviors of secondarily quenched Nylon 6

We observed a very unusual crystallization behavior in Nylon 6 by X-ray diffraction. The melted Nylon 6 films were quenched in oil baths with different temperatures for isothermal crystallization. When the Nylon 6 films were isothermally crystallized above 180 °C for 30 min and then quenched in ice water, three sharp diffraction peaks at 2θ = 9.4, 18.95 and 28.5° were observed in X-ray diffraction patterns. No diffraction peaks could be found at 2θ = 9.4, 18.95 and 28.5° from a series of calculated 2θ values for the α, γ, β and pleated α form crystals of Nylon 6. The locations of these peaks do not correspond with calculated 2θ values. When the film was slowly cooled from the melt state to 180 °C and was maintained at 180 °C for 30 min and then quenched to 0 °C, it could be found that these three reflections disappeared. If the Nylon 6 film isothermally crystallized at 180 °C for 30 min was not quenched to room temperature, but cooled to room temperature in air, these three diffraction peaks could not be observed.