## 3 Results and Discussion
### Dispersion of Functionalized Silica Micro- and Nanoparticles by Ultrasound Micro-Moding Technology
In all cases, a constant char yield was attained at high temperatures, as shown by representative PE99-N 3 and PE99-M 6 specimens in Figure 5a. Furthermore, the remaining weight percentage was always in full agreement with the expected silica content (_i.e._, close to 3 and 6 wt. %). The result is meaningful since it has demonstrated again that particles were not generally retained in the sprue. Silica was effectively led through the feeding channels by the molten polymer, giving rise to well-dispersed specimens. A close resemblance between the TGA and DTGA traces of the micro-molded PE99 sample and the silica-loaded composites was also found during the first stages of degradation (probably also as a consequence of the low content of added particles). The added particles even seem to slightly stabilize the sample (Table 2 and Figure 5). In any case, functionalization of silica particles did not have a negative impact on the ultrasound micro-molding process, as was also observed by GPC measurement. Differences were noticeable only at the end of the degradation process; the presence of shoulders around 483 \({}^{\circ}\)C in the DTGA plots (Figure 5b) seems to be due to decomposition of grafted AMPS groups. \begin{table}
\begin{tabular}{c c c c c c c} \hline
**Polymer** & \(\mathbf{T_{\text{onset}}}\)**(\({}^{\circ}\)C)** & \(\mathbf{T_{\text{10\%}}}\)**(\({}^{\circ}\)C)** & \(\mathbf{T_{\text{20\%}}}\)**(\({}^{\circ}\)C)** & \(\mathbf{T_{\text{40\%}}}\)**(\({}^{\circ}\)C)** & \(\mathbf{T_{\text{max}}}\)**(\({}^{\circ}\)C)** & **Remaining Weight (\%)** \\ \hline PE 99 & 367 & 397 & 411 & 426 & 433 & 0 \\ PE 99-N 3 & 377 & 405 & 415 & 431 & 436 & 2.7 \\ PE 99-N 6 & 377 & 405 & 415 & 432 & 438 & 5.7 \\ PE 99-M 3 & 377 & 405 & 417 & 431 & 437 & 2.9 \\ PE 99-M 6 & 377 & 404 & 419 & 432 & 439 & 5.8 \\ \hline \end{tabular}
\end{table} 
Table 2: Characteristic TGA temperatures and remaining weight percentages for the decomposition of the studied micro-molded specimens. Figure 9: TEM micrographs of the dispersion of functionalized silica microspheres (**a,b**) and nanospheres (**c,d**) in the micro-molded PE99-M 3 and PE99-N 3 specimens. Calorimetric Studies on the Influence of Functionalized Silica Nanoparticles on the Isothermal Crystallization of Poly(nonamethylene Azelate)  
Kinetic analysis was only performed for melt crystallization processes because of the impossibility of obtaining amorphous samples by cooling the melted nanocomposite at the maximum rate allowed by the equipment. Crystallization experiments were therefore carried out in a narrow temperature interval (_i.e._, between 56 and 59 \({}^{\circ}\)C) due to experimental limitations. Figure 10a shows the crystallization exotherms of the neat polyester and the PE99-N 3 nanocomposite, which allowed for determining the time evolution of the relative degree of crystallinity, \(\chi(t)\). The last was calculated according to Equation (1):  
\[\chi(t)=\int_{t0}^{t}\big{(}\mathrm{d}H/\mathrm{d}t\big{)}\mathrm{d}t/\int_{t 0}^{\infty}\big{(}\mathrm{d}H/\mathrm{d}t\big{)}\mathrm{d}t \tag{1}\]  
where \(t_{0}\) is the induction time and \(\mathrm{d}H/\mathrm{d}t\) corresponds to the heat flow rate. The evolution of crystallinity always showed a sigmoidal dependence on time for the five melt crystallization experiments performed for the different samples (Figure 10b). Experimental data were analyzed considering the typical Avrami equation [27; 28]:  
\[1-\chi\left(t-t_{0}\right)=\exp(-Z\cdot(t-t_{0})^{n}) \tag{2}\]  
where \(Z\) is a temperature-dependent rate constant and \(n\) the Avrami exponent whose value depends on the mechanism and geometry of the crystallization process. A normalized rate constant, \(k=Z^{1/n}\), can also be calculated for comparison purposes since corresponding units (time\({}^{-1}\)) are independent of the specific value of the Avrami exponent.