*3.4. Thermal Analysis*

Figure 3a shows the DSC curves of the GA, PA66 films and GA/PA66 films with various weight ratios. The melting temperature (Tm) and melting enthalpy (ΔHm) are summarized in (Table 1). The Tm of the pure GA and PA66 films were 126.50 ◦C and 260.43 ◦C, respectively. It should be noticed that the Tm and ΔHm of the GA/PA66 composite films decreased with the addition of PA66. This might be because the GA nucleation was promoted to generate crystalline regions after the introduction of PA66.

**Figure 3.** (**a**) Differential scanning calorimetry (DSC) and (**b**) thermogravimetric analysis (TGA) curves of the GA, GA/PA66 (2:1), GA/PA66 (1:1), GA/PA66 (1:2), PA66 nanofibers.


**Table 1.** Detailed data of the DSC and TGA thermograms for the nanofibrous films.

1 T10wt% was the temperature at 10% mass loss. 2 Tmax was the temperature at maximum weight loss rate. 3 Wred was the residual weight at 600 ◦C.

> Figure 3b shows the TGA curves of the nanofibrous films, and the details were provided in (Table 1). The results indicate that there was a weight loss in the period from 50 to 260 ◦C, which was related to the vaporization of moisture [40]. After approximately 300 ◦C, a higher loss of nanofiber films resulting from polymer decomposition was recorded. The decomposition of GA occurs at about 300 ◦C, while the decomposition of PA66 at around 420 ◦C was observed. As the temperature hits 600 ◦C or higher, the mass of the films tended to be stable, indicating that the decomposition of the films was complete. At the completion of the TGA, the residual weights of the pure GA and PA66 films were 21.04% and 2.95%, respectively. The residual weights of the GA/PA66 composite films were 16.20%, 13.50% and 9.70%, corresponding to weight ratios of 2/1, 1/1 and 1/2, which were negatively correlated with the weight of PA66. The above results revealed that the residual amount of the composite films was reduced, while the rate of decomposition and the maximum decomposition temperature increased.
