Résumé
In the aim of resolving environmental key issues such as irreversible soil pollution by non-biodegradable and non-recoverable polyethylene (PE) fragments, several biodegradable films based on poly(butylene adipate-coterephtalate) (PBAT/PLA, PBAT/PPC and PBAT/Starch) have been tested as mulch films in real field conditions. The impact of outdoor ageing on film's mechanical and functional properties was investigated both on films exposed at the soil surface and buried into the soil in order to assess the respective contribution of the main related ageing factors 1 e UV radiations and microorganisms. The early loss of integrity of the biodegradable materials occurred concurrently and was attributed to the crosslinking of polymer chains induced by UV radiations. Considering that the major part of the three materials studied is made of PBAT, even if probably from various origins and containing different aliphatic/aromatic ratios, this suggested that the nature of the other polymer constituting the blend would not have a significant impact on the ageing mechanism of the material. The first signs of biodegradation were noticed on the soil-facing surface of films 18 months after installation without previous burying step. Biodegradation analyses conducted by respirometry in a compost medium indicated that field ageing had a low impact on the kinetics of mineralization and led to similar percentages according to whether the materials had previously been aged or not.