## 3 Results and Discussion
### Thermo-Mechanical Properties  
Figure 6 shows the evolution of the storage modulus (_G_') and the dynamic damping factor (_tan_\(\delta\)) as a function of the temperature of BioEP resin and BioEP composites reinforced with 10 wt% and 40 wt% of CFF and FFF. On the other hand, Table 3 shows the storage modulus at 40 \({}^{\circ}\)C and 110 \({}^{\circ}\)C, as well as the glass transition temperature (\(T_{\text{g}}\)), obtained from the peak maximum of the _tan_\(\delta\) curve for all considered composites. Figure 6: A comparative plot of the dynamic mechanical thermal analysis (DMTA) behavior of BioEP and BioEP/FF composites reinforced with CFF (10 and 40 wt%) and FFF (10 and 40 wt%): (**a**) storage modulus (_G_’), and (**b**) dynamic damping factor (_tan_\(\delta\)). The storage modulus (\(G^{\prime}\)) (Figure 6a) shows different behavior depending on the filler content. As shown in Table 3, the addition of a lignocellulosic filler into the BioEP resin hardly affects the storage modulus at low temperatures (40 \({}^{\circ}\)C), resulting in very similar G' values to the unfilled BioEP resin. However, at high temperatures (110 \({}^{\circ}\)C), it can be seen more clearly how the filler content leads to an increase in \(G^{\prime}\). As observed in Figure 6a, \(G^{\prime}\) increases as the filler content increases, resulting in more rigid materials as the FF content increases. This is because the particles give rise to a high degree of mechanical restriction since they act as interlock points that reduce the mobility of the polymeric 3D-thermosetting net and their deformation ability. This phenomenon is much more pronounced at high temperatures when the chain motion or vibration is greater [22; 61]. Comparing the composites according to the type of reinforcement, it can be seen that the reinforced composites with coarse particles (CFF) have a higher modulus at high temperatures, thus showing their higher capacity to maintain the mechanical load with recoverable viscoelastic deformation at high temperatures compared to the FFF-reinforced composites [56]. Figure 6b shows the dynamic damping factor (_tan_\(\delta\)) evolution regarding temperature. As can be seen, the BioEP resin curve has the highest value of _tan_\(\delta\); however, this value decreases as the FF content in the matrix increases. This decrease is due to the attenuation that the addition of the filler stiff domains causes in the resin since filler particles act as a steric hindrance [56]. As shown in Table 3, the \(T_{\text{g}}\) of the BioEP resin, obtained from the peak maximum of the dynamic damping factor, is around 92 \({}^{\circ}\)C. After the addition of the lignocellulosic filler, the \(T_{\text{g}}\) remains almost constant, with slight changes due to the restriction that the rigid particles randomly dispersed in the epoxy matrix cause [51]. Comparing both composites, it can be seen that the \(T_{\text{g}}\) decrease is slightly higher for FFF-reinforced composites, with a \(T_{\text{g}}\) of around 89 \({}^{\circ}\)C for all of them, on the other hand, it can be seen that \(T_{\text{g}}\) obtained for CFF-reinforced composites is about 90 \({}^{\circ}\)C. This slight difference in \(T_{\text{g}}\) between the two composites may be because the smaller size of the particles and the greater dispersion of them in the matrix results in greater interaction between the filler and the matrix and, therefore, the mobility of the polymer chains in these regions are more restricted [67]. Despite this hypothesis, the changes in \(T_{g}\) are so slight that it is not possible to hypothesize a remarkable effect of the filler on \(T_{\text{g}}\). In addition, it is worthy to note that FF has been obtained after cold-pressing flaxseed and some residual oil could be present in the flour, thus explaining this slight decrease in \(T_{\text{g}}\)[68]. To analyze the dimensional stability of the obtained composites, the coefficient of linear thermal expansion (_CLTE_) was determined by thermomechanical analysis (TMA).