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International audience

This poster was presented by Astrid Delorme at the 32nd annual SETAC Europe meeting in Copenhagen 15th-19th of May 2022, under the “8.04 – Late Breaking Science Extended Submission” session. Abstract: SEALIVE (Strategies of circular Economy and Advanced bio-based solutions to keep our Lands and seas alIVE from plastics contamination) is a H2020 innovation project, which vision is to reduce plastic waste and contamination on land and in seas by boosting the use of biomaterials and contributing to the circular economy with cohesive bio-plastic strategies. As part of WP7, polymer degradation is investigated in several real service life and end-of-life conditions, in order to assess the life cycle of polymers and to eventually develop international biodegradation and ecotoxicity standards for bioplastics. Particularly, urgent concerns of polymers’ end-of-life are focused on the potential hazards and risks associated with microplastics. A prevailing source of microplastics is the fragmentation of larger plastics or product wear, however studies on the rates of fragmentation of polymers under various conditions are scarce [1, 2]. Photodegradation of polymers leads to structural changes of the polymer backbone, such as oxidation with formation of carbonyl functional groups, chain scission and cross-linking [3, 4]. These transformations at molecular level impact the overall mechanical properties of the plastic and favour embrittlement and fragmentation, leading to the generation of micro- and nano-plastics. Understanding the fragmentation rates and behaviour of photo-aged macroplastic generating secondary microplastics will provide vital information to enable a full risk-assessment of plastics needed for international biodegradation and ecotoxicity standards. Here we present a comparative study between a photoaged conventional polymer, polytethylene (PE), and an emerging biopolymer, polylactic acid (PLA), with a focus on the interrelation between photoaging and brittleness. Changes in morphological and physico-chemical properties of the photoaged polymer films are followed through the use of melt rheology, DSC, FTIR, UV-VIS, SEM and durometry with the aim to identify most relevant polymer properties, such as molecular weight, crystallinity and tensile properties that could explain the brittleness and fragmentation behaviour of aged polymers. In this work, we demonstrate the relationship between the brittleness behaviour of the aged polymers with the crosslinking and chain scission mechanisms which occur during the photoaging. [1] A. A. Koelmans, N. H. Mohamed Nor, E. Hermsen, M. Kooi, S. M. Mintenig, J. De France. Water Res., 2019, 155, 410-422. [2] M. Kooi, A. A. Koelmans. Environ. Sci. Technol., 2019, 6 (9), 551–557. [3] S. Commereuc, H. Askanian, V. Verney, A. Celli. Macromol. Symp. 2010, 296, 378–387. [4] S. Commereuc, H. Askanian, V. Verney, A. Celli, P. Marchese, C. Berti. Polym. Degrad. Stab. 2013, 98, 1321–1328.

International audience; In the field of biodegradable polymers such as poly(Lactic Acid) (PLA), it is quite well known that their kinetics of hydrolysis strongly depend on the pH of the hydrolyzing medium. The idea explored during this study focused on PLA, is the addition of additives that are able to control the pH of water when it diffuses inside the polymer. For instance, acids (i.e. succinic acid, also used as food additive) are bio- and eco- friendly additives that are able to play this role. In order to control the release of these molecules and their dispersion inside the polymer, their intercalation in biocompatible nanofillers like layered double hydroxides (LDH) is here considered. The additives have been dispersed in the polymer by melt compounding, commonly used in the plastic industry. Several composites of PLA (4032D) and LDH intercalated with organic acids (succinic, fumaric, and ascorbic acid) have been obtained by an extrusion process. From all extruded materials, PLA films obtained by compression molding were then subjected to hydrolysis tests. The results showed that the mentioned molecules, dispersed in the polymer, are able to control the rate of hydrolysis, and experimental results show an increase of degradation time for samples containing LDH-organic acid (in particular with LDH-succinic acid), making such hybrid additives an appropriate and efficient solution for PLA.

International audience

International audience; On sait maintenant que la plus grande majorité des microplastiques trouvés dans les mers et océans proviennent des terres et à ce titre les environnements eaux douces (rivières et berges) jouent un rôle majeur dans ce processus. Il faut donc imaginer le scénario qu'un plastique usagé, devenu un déchêt après usage, se retrouve dans l'environnement s'il est sorti, pour une raison ou une autre, d'une filière de collecte et de recyclage. Son séjour dans l'environnement peut durer très longtemps et ce déchêt va alors être exposé à un ensemble de contraintes environnementales (UV, pluie, vent, érosion mécanique,..) qui vont poursuivre et amplifier sa dégradation, conduisant à sa fragmentation depuis le macroplastiques en microplastiques, voire en nanoplastiques. Les travaux que nous avons engagés se déclinent suivant deux projets: 1/ Le projet Riverplast (ICCF/ Observatoire du microplastique): Les objectifs du projet Riverplast sont de: - Prélever et analyser la composition de microplastiques dans les eaux de surface de différentes rivières (Allier, Charente, Loire, Touvre,..). Pour cela, nous nous appuyons sur des opérations de science citoyenne, en particulier grace à l'apport du filet de prélèvement babyleg [1,2] qui permet de multiplier les prélèvements et les analyses. 2/-Le projet Plasticcages (ICCF/GEOLAB-PEPS CNRS INEE 2015) : macro et microPLASTIques dans la rivière allier: oCCurrence spAtiale, méthodoloGies analytiquEs et modélisation de la fragmentation [3, 4] Les objectifs du projet Plasticcage sont de: - cartographier la densité de macroplastiques présents sur les rives et son évolution au cours du temps sur un site expérimental de la rivière Allier, et lier cela à la densité du couvert végétal. - Mettre en place sur site une pollution contrôlée. - Analyser la composition du gisement et son évolution au cours du temps. - Analyser la composition de microplastiques extraits des sédiments, en particulier à l'entrée du bras mort, zone ou peuvent exister des tourbillons d'écoulements.

The disposal of polymeric waste is increasingly becoming an issue of international concern. The use of biodegradable polymers is a possible strategy to face most of the problems related to the disposal of the durable (non-biodegradable) polymers. Among biodegradable polymers, PLA (obtained from renewable sources) is a very attractive one, due to its good processability, biocompatibility, interesting physical properties. Hydrolysis is the major depolymerisation mechanism and the rate-controlling step of PLA biodegradation in compost. The propensity to degradation in the presence of water significantly limits specific industrial applications such as automobile, biomedical, electronic and electrical appliances, agriculture. Therefore the control of biodegradation rate is somewhat even more important than the characteristic of biodegradability itself. This is the reason why it is critical to find additives able to modulate the biodegradation rate of biodegradable polymers in relationship to the expected lifet...

This thesis is part of the subject photodegradation and biodegradation of polymer that can be or not from renewable resources. Its main objective is to study the photochemical durability of various polymers or polymer blends used particularly in agriculture and therefore subject to weathering. The chemical structure of polymers is one of the main parameters that could influence the photodegradation. A set of (co)polyesters containing units aliphatic, cyclic and / or aromatic have been selected in order to express the relationships structure / photodurability. The photoageing of materials was carried out under natural and accelerated conditions. Photo-oxidation mechanisms have been suggested for each material based on the evolution of the viscoelastic properties reflecting the macromolecular structure. In this context, the study of the durability of these ecofriendly materials should address in highly complex systems in which each component is subject to change. This feature requires the development of a methodology to determine the composition of a biocomposite and monitor the changes during ageing at the same time as changing the structure of these materials., Ce travail de thèse s’inscrit dans les thèmes de la photodégradation et de la biodégradation de polymère pouvant être ou non d’origine renouvelable. Il a pour principal objectif d’étudier la durabilité photochimique de différents polymères ou mélanges de polymères utilisés en particulier dans l’agriculture et donc soumis à un vieillissement climatique. La structure chimique des polymères est un des principaux paramètres susceptible d’influencer la photodégradation. Un ensemble de (co)polyesters comportant des unités aliphatiques, cycliques et / ou aromatiques a été sélectionné dans le but d’exprimer une relation structure / photodurabilité. Le photovieillissement des matériaux a été réalisé en conditions naturelles et en conditions accélérées. Des mécanismes de photo-oxydation ont été proposés pour chacun des matériaux à partir de l’évolution des propriétés viscoélastiques traduisant celle de la structure macromoléculaire. Dans ce contexte, l’étude de la durabilité de ces matériaux respectueux de l’environnement doit s’intéresser à des systèmes extrêmement complexes dont chaque constituant est susceptible d’évoluer. Cette caractéristique exige de mettre au point une méthodologie permettant de déterminer la composition d’un biocomposite et d’en suivre les modifications en cours de vieillissement en même temps que l’évolution de la structuration de ces matériaux.

International audience; The knowledge of the photodegradation mechanisms and the possibility to modify them is a very important topic, especially for the novel biopolymers, as their durability with respect to the petro-plastics is yet an open question. Among the biopolymers, aliphatic polyesters are an emerging class of materials, thanks to the possibility of preparing them from renewable resources and their potential environmental degradability. In this study two aliphatic molecular structures, containing 1,4-cyclohexylene units, have been used: poly(butylene 1,4-cyclohexanedicarboxylate) (PBCHD) and poly(1,4-cyclohexylenedimethylene 1,4-cyclohexanedicarboxylate) (PCCD). Moreover, in order to increase the durability, titanium dioxide (TiO2), known for its capability of absorbing UV radiation, was incorporated into the polymer. Therefore, composites containing different amount of titania, in the anatase and rutile crystalline phases separately, have been prepared by using a Brabender mixer. Both matrixes and composites were exposed to UV irradiation in an accelerated photo-ageing device and the modifications in their chemical structures were analysed by UV and IR spectroscopies. It results that the photodegradability of PBCHD, containing only one cycle per repeating unit, is lower than that of PCCD and that the composites have a photodegradability lower than those of the homopolymers. The well dispersion of the particles and the good adhesion between TiO2 and polymer have been checked by SEM observations. The protection of TiO2 against the photooxidation increases with the particle content and results higher for the anatase crystalline phase.