## 3 Results and Discussion
### Mechanical Testing, Thermal Characterization, and Contact Angle Measurement  
Electrospun mats fixed in a paper frame were mounted in the tensile tester and investigated to determine the Young's modulus and strain at break. A significantly lower value (\(p<0.05\)) of tensile strain (%) could be observed for PCL_4555, PCL_BG10, and PCL_BGZn compared to the value of PCL electrospun mats (Table 3).  
Figure 4: FTIR spectra of PCL, PCL_4585, PCL_BG10, and PCL_BGZn electrospun mats before immersion in SBF solution. The indicated peaks are discussed in the text.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Sample Name** & **Tensile Strain (\%)** & **Young’s Modulus (MPa)** & **Contact Angle (\({}^{\circ}\))** \\ \hline
**PCL** & \(496\pm 20\) & \(12\pm 1\) & \(104\pm 17\) \\ \hline
**PCL\_4555** & \(95\pm 1\) & \(4.5\pm 0.9\) & \(105\pm 11\) \\ \hline
**PCL\_BG10** & \(221\pm 14\) & \(12\pm 3\) & \(96\pm 2\) \\ \hline
**PCL\_BGZn** & \(113\pm 18\) & \(12\pm 2\) & \(104\pm 19\) \\ \hline \hline \end{tabular}
\end{table}
Table 3: Tensile strain, Young’s modulus and contact angle values for PCL, PCL_4555, PCL_BG10, and PCL_BGZn.  
In the same table the Young's modulus is reported. Generally, the decrease of the value of tensile strain (%) could be correlated with the incorporation of bioactive glass particles in PCL matrix. Bioactive glass particles weaken the entire composite electrospun mat in terms of displacement because the particles act as rigid inclusion inside PCL matrix, as already reported in [9].  
Furthermore, the contact angle was measured as it provides unique insight into how the surface will interact with the external world. A drop of liquid on a solid surface represents a powerful but simple method to investigate the properties of the surface [69]. A change in the contact angle of PCL electrospun mats and composite (PCL_45S5, PCL_BG10, and PCL_BGZn) electrospun mats could be an indicator of successful surface modification. However, contact angle also relies on both the porosity and roughness of the surface of electrospun mats. Generally, when a drop of water is placed on electrospun fibers only a fraction of water encounters the fibers, decreasing the liquid-solid interactions and increasing the liquid-air interactions. This leads to higher contact angles compared to that measured for smooth surfaces, like films [70]. Moreover, when measuring contact angles of electrospun mats it is difficult to estimate the circular part of the drop profile with the surface when it is irregular. However, as expected, the results showed hydrophobic behavior for all samples (Table 3). The bioactive glass particles incorporated in the PCL matrix seems not to affect the hydrophobic behavior of PCL electrospun mats because the values of contact angle were comparable for all samples.  
PCL decomposition was investigated by TG/DTA analyses (Figure 5). Generally, PCL shows single stage thermal degradation [71]. PCL decomposed completely in the region 350 \({}^{\circ}\)C to 420 \({}^{\circ}\)C (Figure 5) where a significant weight loss is recorded [72]. Each exothermic peak at around 450 \({}^{\circ}\)C represent the T\({}_{\text{max}}\) (i.e., the maximum degradation rate) [67]. The residual weight in PCL_45S5, PCL_BG10, and PCL_BGZn was due to the presence of bioactive glass particles embedded in the PCL fibers. For PCL_45S5 the amount was similar to the initial amount added in the polymeric solution, while for PCL_BG10 and PCL_BGZn it was less than 5% wt (the residual weight was 2.25 wt% of BGMS10 and 3.33 wt% of BGMS_2 Zn). In fact, the mass loss after heating was 95.25% for PCL_45S5, 97.75% for PCL_BG10, and 96.67% for PCL_BGZn.  
Figure 5: TG/DTA analyses of PCL, PCL_45S5, PCL_BG10, and PCL_BGZn.