## 3 Results and Discussion
### Mechanical Properties
For example, for the PS + 40/50/70% GTR, the following values of breaking strength are: 19.07, 15.93, 11.80 MPa, respectively, and for EVA compounds + 40/50/70% GTR, the values of breaking strength of 7.02, 5.70, 5.46 MPa, respectively, are obtained, from which they already represent less than 50% of the resistance (MPa) of the polymeric matrix (the polymer without GTR). In general, analyzing the graph of elongation at break (Figure 7a), materials that have special characteristics of elongation at break are highlighted; these are basically, very prominently, the EVA copolymer (704.6%) and in second place is the PP polymer (346.71%). From the addition of GTR particles, the elongation properties of PP dramatically fall, and only for particles of sizes \(<\)200 \(\upmu\)m there is a certain attenuation of this considerable fall of the elongation. Comparatively, the polymer with better elongation properties is the EVA and with percentages of GTR of up to 10-20%, a good behavior to the elongation is observed: EVA + 10% GTR: 438%; EVA + 20% GTR: 351.53%. For particles of sizes \(<\)200 \(\upmu\)m, however, for the PP with the same percentage (10-20%), its elongation behavior is very poor, reaching 15% of the polymer without reinforcement (PP + 10% GTR: 41.73%; PP + 20% GTR: 33.89%). For the rest of materials, there is the PS and the HDPE that have certain elongation properties, although they do not reach values of 100% elongation at break (PS: 66.27%, HDPE: 50.12%). The addition of GTR negatively affects these properties, but suffers a certain drop in % elongation to percentages of 20% GTR (PA + 20% GTR: 23.30%, HDPE + 20% GTR: 20.01%) which already represents percentages less  
Figure 7: (**a**) Elongation at break (%), (**b**) toughness (**f**) for seven polymers/GTR concentrations and particle size \(<\)200 \(\upmu\)m.  
than 50% of the polymer matrix. Is observed that for elongation at break of the GTR compounds (for particle sizes \(<\)200 \(\upmu\)m) [24; 25], the optimum behavior is for EVA compounds, which go from 704% to 528%, 437%, and 351%, which means decreases of 29%, 43%, and 50% for GTR concentrations of 5%, 10%, and 20%, respectively. From 40% concentration, the values are always lower than 3.5 times those of pure EVA. Is seen that the reduction of deformation capacity of the elastomer influences the decrease in elongation, and the decrease in elongation at break is related to the imperfect interfacial adhesion between components. The rest of the polymers have very low values for the elongation at break and toughness properties. The incidence of poor adhesion between phases is a particularly important result [26; 27]. From the comparative graph of toughness (J), it can be concluded that the materials analyzed have very heterogeneous characteristics of energy at break or hardness, and subsequently, the decrease of hardness, and we have similar behaviors of the toughness property for the EVA/GTR composites. Regarding toughness, these drops are even greater. Actually, the toughness goes from 72.3 J for pure EVA to 40 J or 29.2 J for 5% and 10% GTR concentrations. It will decrease even more for larger particle sizes. For concentrations above 20%, considerations on the particle's size or the percentage of GTR are not important at all, since even 10 J of energy are not reached in any case, and it means that these values are seven times lower than the original EVA. Of all of compounds analyzed, those that have a greater energy to the break are: EVA, PP, and in a second level, ABS and HDPE polymers would be located. The EVA polymer stands out at 72.32 J and, secondly, the PP polymer (64.22 J) is located in a very similar range of values. From the addition of GTR particles, the properties of the energy at break (J) dramatically decrease. For PP with 10-20% of GTR, the breaking energies of the compound decrease significantly, from 5.84 J-4.99 J.