The effect of the degree of grafting (DOG) on the thermal behavior of poly(vinylbenzyl chloride)-grafted poly(ethylene-co-tetrafluoroethylene) (ETFE-g-PVBC) films was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), dynamic mechanical analysis (DMA), FT-IR, and thermogravimetric analysis (TGA) instruments. Several ETFE-g-PVBC films with various degrees of grafting, including 10, 24, 41, 60, and 94%, were prepared using a radiation grafting technique. The DSC and XRD results of the ETFE-g-PVBC films revealed that the crystallinity of the films decreased as the DOG increased. The DMA and FT-IR results of the films indicated that a crosslinking reaction occurred at temperatures above 250 degrees C. In the thermal properties of the grafted films, an increase in the DOG led to an increase in the decomposition temperature. The activation energy (E-a) of the thermal decomposition was calculated using Kissinger's equation from TGA results. The E-a value of the PVBC graft chain was found to increase as the DOG increased, indicating that the crosslinking reaction of ETFE-g-PVBC films increased with an increase in the DOG during the thermal degradation process. (c) 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2014, 52, 517-525