Two kinds of amorphous nylon 6 films iodinated before forming from the powders iodinated with 0.2N and 1.0N I-2/KI aqueous solutions were prepared by a melt-press, and isothermally treated at 20 to 80degreesC for 1 day to 20 days. Thermal analyses were performed to investigate mainly the crystallization behavior on the treatment. The DSC thermograms for the treated films exhibit three temperature-groups of endothermic peaks at 60 similar to 70degreesC, 105 similar to 120degreesC, and higher than 150degreesC, which may be associated with the melting of the complex crystal, the relaxed gamma-crystal, and the relaxed a-crystal, respectively. The film containing less I-2/KI and treated at the higher temperature exhibits the peaks associated with the more stable type of crystal. The peak temperature generally increases with the treating temperature and time. On the occasion of there being two peaks associated with the gamma-crystal and the alpha-crystals, DeltaH for the a-crystal increases while that for the gamma-crystal decreases with increasing the treating time. The TG curves indicate two temperature-zones of weight loss by the volatilization of I-2 from I-5(-) and the decompositions of I-3(-) and nylon 6. With increasing treating temperature, the % weight loss by the volatilization of I-2 decreases, and consequently the temperature of the weight loss by the decomposition of nylon 6 increases. (C) 2004 Wiley Periodicals, Inc.