## 3 Results and Discussion
### Characterization and Properties of Hybrid Foams ss-CRMFoams@PCMs  
#### 3.2.1. Leaching Tests and Thermal Properties  
Leaching tests were performed for the CRMFoam-2.5 according to the procedure explained previously. However, only the leaching test results from the CRMFoam-2.5 sample are presented representatively, since CRMFoam-5 showed similar behavior. Table 3 provides a clearer insight about the successful paraffin entrapment, especially after the leaching tests, where no significant quantity of paraffin onto the filter papers was observed. The weight increase constituted a first indication that both RT18 HC and octadecane were encapsulated into the porous framework of the foams, while the slight weight loss after leaching tests confirmed the successful paraffin penetration, even at 80 \({}^{\circ}\)C, which is much higher than the melting point of both paraffins. Furthermore, the paraffin loading results were in good agreement with the TGA results, indicating that the CRMFoams were able to adsorb and retain large paraffin amounts. In fact, the TGA curves of ss-CRMFoam-2.5@OD and ss-CRMFoam-2.5@RT18 revealed the PCMs' loading level of paraffins in the stabilizer matrix of CRMFoam-2.5 and how the encapsulation process affected their thermal stability. According to TGA curves of octadecane and RT18 HC, these PCMs appeared a one-step  
Figure 5: Representative compressive stress-strain curves of CRMFoam-2.5 and CRMFoam-5. thermal decomposition, with onset and endset decomposition temperatures in the range of 170-190 \({}^{\circ}\)C and 200-240 \({}^{\circ}\)C, due to the volatilizations of paraffins [58, 59, 60]. Based on these findings, Figure 6 presents the TGA thermograms for the PU template foam and the CRMFoam-2.5, before (CRMFoam-2.5) and after paraffin entrapment with organic PCMs, n-octadecane, and RT18 HC (ss-CRMFoam-2.5%OD, ss-CRMFoam-2.5%RT18). As can be seen from the image, the TG curve of the commercial polyurethane foam showed a first thermal degradation at 343 \({}^{\circ}\)C and a second at 420 \({}^{\circ}\)C, where it lost almost all of its weight. The successful carbonization is obvious by the TG curve of the CRMFoam-2.5, in which no weight loss is present until 800 \({}^{\circ}\)C, pinpointing the excellent thermal stability of the sample. With paraffin incorporation, the temperature of the carbon foam rose compared to pure paraffins, to 276 \({}^{\circ}\)C for octadecane and 246 \({}^{\circ}\)C for RT18 HC, respectively, indicating that strong connecting bonds to the matrix were accomplished. Additionally, the temperature shifts demonstrate that the paraffin was successfully encapsulated into the carbon foam's pores in both samples and thermal stability was substantially improved. In Figure 7, the results of the leaching tests after 8 h at 30 \({}^{\circ}\)C and after 72 h at 80 \({}^{\circ}\)C are presented. For the first case (30 \({}^{\circ}\)C for 8 h) the ability of the pores to hold the PCMs during the melting process was examined. As seen from the image in Figure 7b, no oily marks are apparent onto the filter paper. For the second one (80 \({}^{\circ}\)C for 72 h), the ability of the pores to maintain the encapsulated PCMs in a temperature above the melting point of the  
Figure 6: Thermogravimetric analysis (TGA) curves of PU foam CRMFoam-2.5, and ss-CRMFoam-2.5%OD ss-CRMFoam-2.5%RT18 hybrids (OD: Octadecane, RT18: RT18 HC). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Foam Sample**} & **Initial Weight** & \multirow{2}{*}{**PCM Paraffin**} & **Final Weight** & **Paraffin** & \multirow{2}{*}{**Paraffin Loading**} \\  & & & **(before** & **(after Leaching** & **Loading** & **DTA/TG** \\  & **(g)** & & **Leading Tests** & **(g)** & **(wt\%)** & **(wt\%)** \\ \hline \multirow{2}{*}{CRMFoam-2.5} & 2.9816 & RT18 HC & 9.6545 & 8.5260 & 65.0 & 61.18 \\  & 2.1430 & Octadecane & 6.7849 & 6.3567 & 66.3 & 48.70 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Summary of the CRMFoam-2.5 sample’s weight before and after leaching tests and PCM loading.