## 3 Results and Discussion
### Differential Scanning Calorimetry Analysis  
Figure 4 illustrates the DSC thermograms for PP composites reinforced with glass fiber, elastomer, and treated ash powder. Notably, the primary findings that are specific to the \(\alpha\) crystalline phase of PP, Tc (maximum of the crystallization exotherm), Tm (maximum of the melting endotherm) and melting/crystallization enthalpy (\(\Delta\)Hm/\(\Delta\)Hc), are laid out in Table 4. DSC analysis showed that the Tm of the composites has very small variations across the composites by 0.4-0.7 \({}^{\circ}\)C, while Tc does not change. The lowest value for Tm was observed for the PP-25G-C-E composite. This behavior could be explained by the simultaneous influence of fly ash, SEBS, PP-MA, and glass fiber on the chain mobility of PP. From the DSC and XRD results it can be seen that Tm is affected by the crystallite size rather than percentage crystallinity. The larger the crystallite, the narrower the melting range. In the case of sample PP-25G-C-E, the crystallite according to the XRD results is larger and  
Figure 3: TGA and DTGA curves of E, PP-25G, PP-30G, PP-25G-E, PP-25G-C and PP-25G-C-E composites. the sample melts at 160.8 \({}^{\circ}\)C, but in a larger melting range (the difference between Tm and onset is 8.5 \({}^{\circ}\)C). In the case of sample PP-25G-E, the crystallite is smaller according to the XRD results and the sample melts at 161.5 \({}^{\circ}\)C, but in a narrow melting range (the difference between Tm and onset is 4.3 \({}^{\circ}\)C). The \(\Delta\)Hm/\(\Delta\)Hc are reduced significantly, as seen in Table 4, with the introduction of elastomer and slightly less with the introduction of treated ash. By adding treated ash, the degree of crystallinity does not change, and melting/crystallization enthalpy decreases by almost 7% compared to PP-25G. The addition of elastomer leads to an increase in the degree of crystallinity by almost 20% and a decrease in melting/crystallization enthalpy by almost 12% for PP-25G-E and by 20-27% for PP-25G-C-E. The degree of crystallinity of PP is calculated by the following equation:  
\[\text{X}_{\text{C}}(\%)=\frac{\Delta\text{H}_{\text{m}}}{(1-\mathcal{O}) \Delta\text{H}_{\text{m}}^{\text{o}}}\times 100\%\]  
where \(\text{X}_{\text{C}}\) is the crystallinity, \(\Delta\text{H}_{\text{m}}\) is the apparent enthalpy of crystallization for the composite, \(\Delta\text{H}_{\text{m}}^{\text{o}}\) is the enthalpy corresponding to the melting of 100% crystalline isotactic PP and \(\varnothing\) is the weight fraction of the components incorporated in the polymer matrix; \(\Delta\text{H}_{\text{m}}^{\text{o}}\) of PP is 209 J/g according to previous studies [42; 43]. The degree of crystallinity, \(\text{X}_{\text{C}}\), varies in the order PP-25G-C-E \(>\) PP-25G-E \(>\) PP-25G-C \(>\) PP30G \(>\) PP-25G and is influenced by the level of interaction among the components. These results are consistent with the results obtained by FTIR analysis for the crystallinity index. It is notable that the addition of elastomer leads to an increase in crystallinity, which, according to studies by [PERSON] et al. [44] and by [PERSON] et al. [45], implies that SEBS accelerates the crystallization process by acting as a nucleating agent for PP and augments its crystallization. A study by [PERSON] et al. [46] explains that strong interfacial bonding  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Cooling, Crystallization**} & \multicolumn{4}{c}{**Melting, 2 nd Heating**} \\ \cline{2-9}
**Sample** & **Onset** & **Tc** & **\(\Delta\)Hc** & **Xc** & **Onset** & **Tm** & **AHM** & **Xc** \\  & \({}^{\circ}\)C & \({}^{\circ}\)C & **J/g** & \% & \({}^{\circ}\)C & \({}^{\circ}\)C & **J/g** & \% \\ \hline PP-25G & 124.8 & 122.4 & 78.4 & 50.01 & 156.8 & 161.5 & 69.55 & 44  
exists between PP and SEBS due to the chemical structure of PP being close to that of the midblock of SEBS.