## 3 Results and Discussion  
### FTIR-ATR and Granulometry Analyses  
The results of the FTIR-ATR analyses are shown in Figure 5. The different bands are linked to the existence of particular functional groups. In the spectrum of the processed virgin polypropylene, it is possible to highlight the six most characteristic groups of bands for this thermoplastic: the four bands between 2951 and 2839 cm\({}^{-1}\), the stretching vibrations of the CH bonds, the band at 1455 cm\({}^{-1}\) that coincides with the asymmetrical bending of CH\({}_{3}\) and the symmetrical band that appears at 1376 cm\({}^{-1}\). Three superposed spectra corresponding to CoP are shown in the lower part of Figure 5, which are the results published in [13]. For the three types of agglomerated cork, samples from wine corks (A, B, C) have been taken as a reference. They exhibit characteristic vibrations of suberin, lignin and polysaccharides, the main constituent of cork. Thus, in the CoP spectrum, the band at approximately 3330 cm\({}^{-1}\) is recognized as the stretching vibrations of O-H bonds. The distinct peaks observed in the bands at 2920 and 2853 cm\({}^{-1}\) are indicative of the stretching vibrations of CH\({}_{2}\) bonds within the alkyl chain of suberin [11]. The band at 1737 cm\({}^{-1}\) is attributed to the stretching vibrations of C=O bonds present in the ester groups of suberin [32]. The two most characteristic peaks of the CoP spectrum are at 1227 and 1091 cm\({}^{-1}\), which correspond to the C-O bond tension typical of the esters of the suberin and secondary alcohols of the polysaccharides, respectively. The spectra associated with the CAG display distinct peaks for CoP, such as those at 1227 and 1091 (marked with arrows), and for PP, such as those at 1455 and 1376 (although the latter are also present in CoP but to a lesser extent). Comparing the evolution of these peaks across the three CAGs in terms of relative proportions reveals a variation in intensity as the proportion of CoP increases. In Figure 6, SEM micrographs of the specimens' fractures are shown. These correspond to the agrocomposites with different CoP contents, indicated at the top of each column, to investigate the morphology and distribution of the structures involved. According to the type of footprint presented in the 75\(\times\) micrographs (the first row), it is possible to determine that the material suffers typical stress fractures with weak spots or small cracks that lead to the crazing of the material. Concerning the 500\(\times\) magnification micrographs (the second row in Figure 6), the examinations performed on the composites enabled the observation of filler particles formed by blending PP with CoP. These particles exhibit micrometric dimensions and are evenly dispersed throughout the plastic matrix without requiring the addition of coupling agents. Figure 4: Elements used to perform the adhesion test. The cork samples named as 1 are bevelled and the others cylindrical. Figure 5: FTIR spectra of CoP and CoP:PP CAG. The absence of empty spaces illustrates a favorable interaction between the cork particles and the polymer matrix [11]. It is possible to distinguish how the agglomerations and the cork microstructure are rendered as hexagonal/pentagonal (honeycomb-like) or rectangular (brick wall-like) patterns, when properly aligned, as shown in the higher-magnification images (the third row). Starting from the mixture at a ratio of 30:70, this starts to be displayed and is most easily seen in the 35:65 mix, where particles of around 200 \(\upmu\)m are observed.