## 3 Results
On the other hand, CM, LF and UG have chemicals modifications in its chemical side groups (see Figure 1) that hinder its mobility, mainly because they are able to interact with TPS hydroxyl groups [43; 49]. However, these chemicals modifications produced a different effect on the mobility of the chains that will further affect the final performance of TPS-resin based formulations. LF is a pentaerythitol ester while UG is a glycerol ester. Thus, TPS-LF would have a higher T\({}_{\text{g}}\) than TPS-UG, as a pentaerythitol ester has higher cohesion, adhesion, viscosity at fusion and glass transition temperature than a glycerol  
Figure 4: Stress–strain curves of TPS and TPS-resin blend formulations with the toughness values. \({}^{\text{a-d}}\) Different letters within the same property show statistically significant differences between formulations (\(p<0.05\)). ester. On the other hand, CM is a modified gum rosin with maleic anhydride that have reactive sites that differ from those in unmodified gum rosin [49], as CM has three carboxylic acid groups, which increases its acidity [49]. As a result, CM, LF and UG shift \(\mathrm{T_{g}}\) to higher temperatures (70 \({}^{\circ}\)C or more). The resins with group modifications had a more marked stiffening effect. In fact, the tendency of increment in \(\mathrm{T_{g}}\) values follows the same tendency as the Young's modulus. The shifts in TPS glass transition temperatures suggest that GR and its derivatives have good miscibility with TPS matrix [37; 50]. With DSC results, it was not possible to establish differences between the \(\mathrm{T_{g}}\) of the TPS-GR and TPS-RD. However, it is possible to determine that LF is the modified resin with the highest stiffening effect because it produced the highest displacement of \(\mathrm{T_{g}}\). In fact, it shifted the \(\mathrm{T_{g}}\) of TPS from 45 \({}^{\circ}\)C to 79.3 \({}^{\circ}\)C, which is 9 \({}^{\circ}\)C more than UG and 7 \({}^{\circ}\)C more than CM. The obtained DSC results are consistent with TPS-LF increment of Young's modulus, TPS-LF and TPS-UG increase in hardness, as well as with the plasticisation behaviour of TPS-GR, already discussed. TGA curves and their derivatives (DTG) for TPS and its TPS-resin blend formulations are shown in Figure 6. The thermal values at different degradations stages, determined by TGA analysis, are shown in Table 2. It can be noticed that the formulated samples were more more stably stable than the neat TPS in all the degradation stages. TGA curves showed a three-step degradation process (Figure 6a). Between 100 \({}^{\circ}\)C and 170 \({}^{\circ}\)C an initial weight loss of 12% occurs, which is related with the bound water content in the TPS samples [51; 52]. The degradation onset temperature (\(\mathrm{T_{5\%}}\)) of TPS (Table 2) increased with the addition of GR and rosin derivatives. GR rises \(\mathrm{T_{5\%}}\) by 29 \({}^{\circ}\)C, CM by 23 \({}^{\circ}\)C, LF does by 25 \({}^{\circ}\)C, while RD and UG produce the lowest increase in \(\mathrm{T_{5\%}}\) by 16 \({}^{\circ}\)C and 11 \({}^{\circ}\)C, respectively. Therefore, the chemical structures of the additives allow them to positively interact with the TPS matrix, providing a thermal stabilising effect [5]. Nevertheless, GR and LF create a higher protection to thermal degradation than the other additives. The increased thermal stability has been related to the  
Figure 5: Differential scanning calorimetry (DSC) second heating scan curves of neat TPS and TPS-resins blend formulations. positive interaction between the carbonyl groups of the pine resins and the hydroxyl groups of the starch material (i.e., hydrogen bonding interactions) [53]. The second step of degradation starts at 260 \({}^{\circ}\)C and it is the main degradation process. In this step the degradation is produced because of the depolymerization of starch [51], that is the cleavage of ether linkages in starch backbone and it is also related with the degradation of the starch/glycerol reach phase [52].