*3.9. SEM Observations*

Figure 8a,b displays the ENS micrographs of surface fracture obtained by SEM.

In Figure 8, it is possible to notice that the presence of pores or cavities in the material (white arrows) is quite reduced, which was already expected due to the low porosity and water absorption and to the manufacturing process that uses vibration, compaction, and vacuum.

The occurrence of displaced particles (Figure 8a) of the matrix can also be observed, as indicated by the arrow. The voids in the interface region point to this displacement. There was little displacement of waste grains (Figure 8a,b), confirming the efficient wetting [17].

The compaction enhances the settlement and adhesion of particles, and the vacuum assists the resin to better penetrate the interstices of the waste particles, filling the void volume [3], which is clearly seen in the micrograph, by a good interfacial adhesion between the waste particles and the resin. The good interfacial interaction is evidence of effective interfacial wetting of the resin, which is directly related to the improvement of the material's mechanical properties, as reported by Miller et al. [39] and Debnath et al. [40]. Figure 8a,b both show intergranular fracture surfaces with evidence of mechanical stress failure, since the fracture cracks pass through the grains indicated by the arrow.

**Figure 8.** ENS-15 scanning electron fractured surface micrographs with different magnifications: (**a**) 200× and (**b**) 500×.
