Abstract
The use of biosourced and biodegradable plastics as substitutes for conventional plastics in food packaging, is an alternative to significantly reduce plastic pollution. Moreover, the integration of these biodegradable plastics into a virtuous cycle of reuse and recycling would preserve raw material resources, and exploit the maximum value of the product. However, these plastics are often uncompetitive due to their thermal instability. The objective of this thesis is to study the impact of natural molecules; polyphenols, on the potential stabilization of a biopolyester derived from microbial synthesis, and biodegradable under natural conditions, PHBV (Poly(3-hydroxybutyrate-co-3-hydroxyvalerate). The stabilizing effect of quercetin and gallic acid is studied during the different stages of the life cycle of a food packaging, from formulation to biodegradation, through reuse and recycling. The two major scientific questions that this thesis attempts to answer are: (i) What are the interactions/relationships between polyphenols and PHBV during the different stages of the life cycle of a food packaging? (ii) What is the impact of polyphenols on the stability of PHBV during these different stages? The first part of this thesis is devoted to the evaluation of the capacity of polyphenols (in terms of quantity and chemical structure) to bring stabilization to the polymer matrix. The second part deals with the influence of polyphenols on the structural evolution (macro- and microscopic) of PHBV during the use/reuse and mechanical recycling stages. Finally, the maintenance of the biodegradability of PHBV, in the presence of polyphenols, is evaluated, in a last part.