## 3 Results and Discussion  
### Filler and Coatings Aspect  
The structural morphology of the bio-based wax additive was initially examined using SEM, as shown in Figure 1. The analysis verified the information provided in its technical data sheet, revealing that the powder is composed of granules characterized by an irregular shape, with an average size of approximately 10 \(\upmu\)m. This size is well-suited for applications like additives and fillers in paints and organic coatings, where typical thicknesses range in the order of tens of \(\upmu\)m. The EDXS analyses, depicted in Figure 11 of the Appendix A, demonstrate the organic composition of the wax-based additive, primarily consisting of carbon and oxygen. This suggests that the filler is devoid of any inorganic elements or contaminants that might affect its performance. Figure 1: SEM micrograph of the bio-based filler, acquired in secondary electrons mode. Thus, the additive was incorporated into the acrylic paint formulation to produce the four series of samples detailed in Table 1, with their appearances illustrated in Figure 2a. The additive exhibits a significant coloring effect, notably altering the appearance of the coating to green-yellow hues. This visual effect becomes more pronounced with increasing additive concentration, evident from the transition from sample G0, which is transparent, to samples G5 and G10, containing 5 wt.% and 10 wt.% of wax, respectively. Simultaneously, the UV absorber included in sample G10U does not counterbalance the chromatic effect of the green tea-infused wax, as samples G10 and G10U exhibit identical appearances. However, to quantify and qualify the aesthetic distinctions among the four series of samples, they underwent colorimetric measurements. Figure 2b displays the values of the three color coordinates L*, a*, and b*. In colorimetry, these coordinates represent specific color attributes, where:  
* L* represents lightness, varying from 0 (for black objects) to 100 (for white objects);
* The a* axis represents the red-green axis, with positive values indicating redness and negative values indicating greenness;
* The b* axis represents the yellow-blue axis, where positive values indicate a tendency towards yellowness and negative values indicate a tendency towards blueness. The inclusion of the _green_ additive results in a decrease in the L* coordinate, indicating slightly darker shades. Additionally, as the additive concentration increases, the value of the b* coordinate rises towards yellower shades. As visually observed in Figure 2a, the simultaneous presence of the UV absorber in sample G10U does not yield any aesthetic impact, as evidenced by the negligible alteration in the values of the three coordinates compared to sample G10. To emphasize the chromatic influence of the bio-based additive, the color change \(\Delta\)E compared to sample G0 was evaluated, and calculated according to the formula [64]:  
Figure 2: (**a**) Visual appearance of the samples, (**b**) respective values of the three CIE Lab coordinates, and (**c**) variations in color \(\Delta\)E relative to the reference sample G0. \[\Delta E=\left[(\Delta L^{*})^{2}+(\Delta a^{*})^{2}+(\Delta b^{*})^{2}\right]^{1/2} \tag{1}\]  
The values of \(\Delta\)E for the three series of composite coatings are depicted in the graph of Figure 2c. There is an almost proportional relationship between the additive concentration and the chromatic alteration of the coating, with \(\Delta\)E values nearly doubling as the wax powder infused with tea increases from 5 wt.% to 10 wt.%. Indeed, sample G5 exhibits a color change compared to the reference sample G0 of approximately 12 units, whereas samples G10 and G10U show a \(\Delta\)E of approximately 20-21 points. These color change values can be deemed substantial, particularly in light of the literature considerations, which define color changes of 1 unit as appreciable even to the human eye [65]. The error bars in Figure 2b,c are narrow, indicating the high reproducibility of the colorimetry measurements conducted.