## 3 Results and Discussion
### Non-Isothermal Crystallization Behavior of P3 HBHrk--Effect of Nucleating Agents
#### 3.1.2 Effect of Nucleating Agents on Non-Isothermal Crystallization of P3 HBHHx
A substantial portion of the polymer remained amorphous after cooling, further confirming its low nucleation efficiency. The addition of nucleating agents had little impact on the melting temperatures (\(T_{\text{m1}}\) and \(T_{\text{m2}}\)) of P3 HBHHx, except in the case of PHB, where a slight increase was observed, as highlighted by the dashed ellipses in Figure 2b. For PHH_05 PHB, the first melting peak increased to 138.1 \({}^{\circ}\)C, and the second peak increased to 152.7 \({}^{\circ}\)C. This shift is likely due to the development of thicker lamellae during the crystallization process (note the difference of more than 40 \({}^{\circ}\)C between the crystallization temperatures of the neat polymer and PHB-loaded sample). Similar but less pronounced effects were observed for boron nitride, where the first melting peak increased to 136.6 \({}^{\circ}\)C while the second melting peak remained unchanged. These results confirm that the addition of nucleating agents can significantly alter the crystallization behavior of neat P3 HBHHx by enhancing the crystallization kinetics and increasing the degree of crystallinity. Among the tested additives, boron nitride and PHB exhibited the highest efficiencies, resulting in faster and more complete crystallization during cooling. Talc and ultrafine cellulose provided moderate improvements, while LAK had a minimal impact. 3.1.3 Effect of Increased Nucleating Agent Concentration on the Crystallization Behavior of P3 HBHHx  
To evaluate whether 0.5 wt% of the nucleating agents was sufficient to enhance the crystallization behavior of P3 HBHHfx, a higher concentration of 2 wt% was also tested. As shown in Figure S1, increasing the concentrations of BN and PHB to 2 wt% resulted in only minor improvements. The \(T_{c}\) increased by approximately 3 to 5 \({}^{\circ}\)C, while \(\Delta H_{\text{c}}\) increased by 2 to 6 J/g (Table S1). These slight increases suggest that the nucleation efficiency of BN and PHB is already near saturation at 0.5 wt%, indicating that higher concentrations are unnecessary. In contrast, talc exhibited a more pronounced concentration-dependent effect on the crystallization behavior of P3 HBHHx. Figure 3 compares the samples with talc loadings ranging from 0.5 wt% to 20 wt%. At 2 wt%, the \(T_{c}\) increased significantly from 66.5 to 72.6 \({}^{\circ}\)C, and the \(\Delta H_{\text{c}}\) increased from 46.3 to 57.1 J/g. Additionally, the cold crystallization peak observed at 0.5 wt% disappeared at 2 wt%, as shown in the inset of Figure 3. These results suggest that talc is considerably more effective as a nucleating agent when present at higher concentrations. This improvement may be attributed to the increased number of active nucleation sites provided by the higher talc content, enhancing the probability of crystallite formation during cooling. In contrast, BN and PHB appear to reach their optimal nucleation performance at 0.5 wt%, as only marginal improvements were observed when their concentration increased to 2 wt%. Therefore, while BN and PHB demonstrate early saturation in nucleating efficiency, talc exhibits a more pronounced concentration-dependent effect. This is likely due to its initial moderate nucleation activity, which becomes significantly more effective as the concentration increases. Higher talc concentrations, including 10 wt% and 20 wt%, were also evaluated and resulted in further improvements in crystallization behavior. However, at these elevated loadings, the large quantity of talc not only affects crystallization but also has a considerable influence on other properties such as mechanical performance, processability, and potentially biodegradability. Therefore, 2 wt% talc was selected for further investigation in the following studies. For ultrafine cellulose (UFC), increasing the concentration to 2 wt% resulted in a more defined and sharper crystallization peak, indicating improved nucleation uniformity and more consistent nucleation site formation.