## 3 Results and Discussion
### Relative Migration Measurement  
The results of the relative migration of additives after 10 days of contact with food simulants are gathered in Figures 4 and 5 for PHBV, PHBV NCP (Figure 4), PBSA and PBSA NCP (Figure 5), and the corresponding UV treated materials. The relative migration values are generally high, reaching 100% in several cases, which reflects a high level of contamination in the case of contact with fatty foods. The values are substantially similar in both types of solvents and very close to the values measured with the same target molecules from synthetic materials such as polyolefins [10]. Overall, the level of migration obviously depends on the  
Figure 4: Comparison of the relative migrations of additives from PHBV, PHBV NCP and the corresponding aged materials to 95% ethanol (**a**) and isootcane (**b**) after 10 days of contact. Figure 3: Overall migration of PHBV, PHBV NCP and the corresponding aged materials to the selected food simulants (3% acetic acid, 95% ethanol and isootcane). nature of the substance, but each compound behaves differently depending on the type of material and the food simulant in contact. The sorption of such polar simulants is known to induce the swelling of the polymeric network, and consequently, modify the transport properties of the material. In addition, the sorption of non-polar solvent is likely to significantly modify the affinity of the compound for the packaging film, and thus impact its migration level. The impact of the presence of nanoclays is difficult to extract and does not follow any particular pattern. The analysis of variance reveals a variable influence of nanofillers depending on the nature of the material and the simulant. In the particular case of PBSA, the addition of a nanoclay has no significant impact when the packaging is in contact with ethanol, whereas it induces a decrease in the level of migration (\(p=0.027\)) as a result of contact with isooctane. On the other hand, the presence of nanoclays does not seem to produce any significant effect on the inertial properties of the PHBV, regardless of the simulant placed in contact. The dispersion of nanoclays is, however, known to impact both the diffusivity of low molar mass molecules by a possible tortuosity effect, and influence the equilibrium state and the partition coefficient by interaction or adsorption effects with the diffusing molecules. For high-barrier polymers in a glassy state at an operating temperature by which the equilibrium is reached slowly, the level of migration measured after only ten days of contact is more specifically related to the diffusion coefficient of the substance. For low-barrier polymers in rubbery states, such as PBSA and PHBV, the measurements carried out after 10 days of contact were performed in an equilibrium state of concentration in both compartments (packaging and food simulant) for each additive. This observation partly justifies the low influence of the presence of nanoclays, whose impact on the diffusion properties of these polymers has already been demonstrated [11]. By looking at each compound independently, the accelerated aging seems to limit the migration of additives. This trend was observed for all substances except in some rare cases (methyl salicate in PHBV in contact with 95% ethanol and in PBSA NCP in contact with isooctane). The analysis of variance carried out on all the data regardless of the nature of the additive shows a significant decrease in the migration value (\(0.0001<p\)-value \(<0.016\)) on both types of films in contact with the two tested food simulants. The box plot in the Figure 6 graphically depicts the effect of the UV aging, which is exercised in similar extent on both bio-polyester-based materials. The variance analysis reveals, in addition, a significant interaction (\(0.0001\leq p\)-value \(\leq 0.014\)) between the UV treatment and the nature of additive, suggesting that the decrease in migration induced by the material aging depends on the nature of the additive.