*3.3. Crystallization and Melting Behavior*

The DSC curves of the PBAT/Ti3C2TX nanocomposites are shown in Figure 3. In Figure 3a, the onset crystallization temperatures of PBAT nanocomposites exhibit an increasing trend with the increase of Ti3C2TX content. In addition, the values of *T*cp for PBAT nanocomposites in Table 2 are 72.1, 73.1, 73.7, and 75.2 ◦C, respectively. The increase in *T*cp indicated that the presence of Ti3C2TX had a heterogeneous nucleation effect, accelerating the formation of crystallites in the PBAT matrix during cooling [41]. It was noted that the values of **Δ***H*<sup>m</sup> were lower than **Δ***H*<sup>c</sup> for the PBAT/Ti3C2TX composites, which can be ascribed to the fast cooling rate. In Figure 3b, the values of *T*mp for PBAT nanocomposites are 119.3, 121.0, 121.6, and 121.0 ◦C, respectively. The increase in *T*mp suggests that the filling Ti3C2TX contributes to the formation of perfect crystallinity of PBAT during the cooling procedure. Moreover, the crystallization degree of PBAT-1.0 had the highest value of 13.4% with the addition of 1.0 wt% Ti3C2TX. When the content of Ti3C2TX was further increased up to 2.0 wt%, the crystallization degree of PBAT-2.0 showed a slight decrease. This may be due to the excessive addition of Ti3C2TX, which led to agglomeration, to some extent. On the other hand, the inhibition effects of the excessive Ti3C2TX nanosheets were more profound than the nucleating effect that led to smaller crystallization and decreased crystallinity [42].

**Figure 3.** Differential scanning calorimetry (DSC) thermograms of PBAT/Ti3C2TX nanocomposites. (**a**) first cooling, (**b**) second heating.


**Table 2.** DSC thermograms of PBAT/Ti3C2TX nanocomposites.

#### *3.4. Mechanical Properties of Casting Films*

Figure 4 shows the typical stress–strain curves for pure PBAT and PBAT/Ti3C2TX nanocomposite casting films, and the corresponding data are summarized in Table 3. It was observed that PBAT-0 exhibited a high ductility (elongation at break ~ 1442%) but low tensile strength (~22.6 MPa), which is consistent with previous report [14]. With the addition of 0.5 wt% Ti3C2TX, the tensile strength of the PBAT/Ti3C2TX nanocomposite increased by 19.8% with a slight increase in the elongation at break. As depicted in Figure 1, the Ti3C2TX had good interfacial interaction with the PBAT matrix; therefore, the addition of Ti3C2TX nanosheets can transform the stress during the tensile process. When the Ti3C2TX content was increased to 1.0%, the PBAT/Ti3C2TX nanocomposite had the maximum tensile strength (31.6 MPa). This enhancement can be ascribed to the reinforcement effects of the nanofillers and the interaction between the stress concentration zones around the Ti3C2TX nanosheets [43,44]. It is worth noting that PBAT-2.0 showed a decreasing tendency in both tensile stress and elongation at break as compared with PBAT-1.0. This may be due to the aggregation of Ti3C2TX nanosheets in the PBAT matrix.

**Table 3.** Tensile properties of PBAT/Ti3C2TX nanocomposite casting films.


**Figure 4.** Tensile stress versus strain of PBAT/Ti3C2TX nanocomposite casting films.
