## 3 Results and Discussion
### Effect of the Filler on the Abrasion Resistance Properties of the Coatings
The roughness values parallel to the substrate fibers (Ra //) remain consistent throughout the test, as the abrasive sponge moves in the same direction as the fibers. Consequently, its movement does not induce significant morphological defects in this direction. Conversely, the values of Ra \(\perp\) are partially altered due to the rubbing action of the abrasive sponge. This phenomenon is notably evident in sample G0, where the values of Ra \(\perp\) undergo a substantial increase during the test, indicating significant morphological alterations. In contrast, this effect is less pronounced in coatings containing the bio-based filler, and in some instances, there is even a reduction in roughness, suggesting a smoothing or \"flattening\" of the surface. Hence, apart from the increased material loss, the abrasive process also induces significant changes in the surface morphology of the acrylic matrix. Both of these phenomena appear to be effectively mitigated by the wax-based additive. To further scrutinize the protective contribution of the filler, the samples were subsequently examined under scanning electron microscopy (SEM) at the conclusion of the test. Figure 15 displays the surface appearance of the coatings after undergoing 3000 scrub test cycles. The images vividly depict a distinct morphological contrast between sample G0 and the three composite coatings. Sample G0 appears significantly impacted by the abrasion process, displaying evident surface deformations characterized by typical abrasion lines caused by the scrub sponge [87; 88]. These observations help elucidate the observed increase in Ra \(\perp\) values illustrated in the graph of Figure 14c. In contrast, the gradual inclusion of wax-based powder results in a specific phenomenon, as noted in prior research [32; 34]: the motion of the scrubbing pad does not remove material; rather, it triggers the plastic deformation of the rice bran wax, known for its pliability even at room temperature [89]. This behavior is characteristic of wax-based additives commonly used to create smooth surfaces [90]. The pad tends to disperse the wax, occasionally reducing the values of Ra \(\perp\), thereby mitigating friction between the coating surface and the pad itself. As a result, the wax's reinforcing capability arises from its capacity to undergo plastic deformation, thereby reducing surface friction. Thus, the coating experiences diminished material loss, as evidenced in Figure 13, as it is not entirely stripped away by the pad but rather spread across the surface of the composite layer. Polyamide 11-based additives exhibit a comparable phenomenon [68], indicating that materials capable of plastic deformation during third-body streaking processes can notably enhance the abrasion resistance of wood coatings. In summary, the bio-based additive reaffirms the established reinforcing capabilities of wax-based fillers, effectively reducing mass loss in coatings subjected to abrasion. The shear stresses generated by the abrasive sponge's movement result in the plastic deformation of the powder, preserving the surface morphology of the coating. Consequently, the green additive demonstrates additional protective functionality, complementing its specific color and barrier effect, making it particularly appealing for use in wood paints. Figure 14: Evolution of (**a**) color, (**b**) gloss, and (**c**) roughness (longitudinal//and perpendicular \(\perp\)) during the scrub test. Figure 15: SEM micrographs of the surface morphology of (**a**) sample G0, (**b**) sample G5, (**c**) sample G10, and (**d**) sample G10U, acquired after 3000 cycles of scrub test.