*3.3. XRD Analysis*

Figure 2b shows the XRD results of the GA, PA66 films and GA/PA66 films with various weight ratios. PA66 has two obvious diffraction peaks at around 2θ = 20.1◦ ascribed to the interchain hydrogen bond plane of the amide group [29] and 2θ = 23.7◦, which is similar to the results of Noguchi's study [39]; whereas gelatin had a broad diffraction peak at 2θ = 19.2◦, suggesting a low crystallinity of GA. For the GA/PA66 composite films, two diffraction peaks appeared between 20◦ and 25◦, which were corresponding to the two characteristic peaks (α1 and α2) of the α-crystalline form of PA66 [38]. It was noticeable that the intensity of the peaks of the GA/PA66 composite film was enhanced compared to the pure GA film, suggesting that the crystallization of the GA/PA66 composite films was advanced with the addition of PA66.
