Structure and Barrier Properties of Multinanolayered Biodegradable PLA/PBSA Films: Confinement Effect via Forced Assembly Coextrusion

Multilayer coextrusion processing was applied to produce 2049-layer film of poly(butylene succinate-co-butylene adipate) (PBSA) confined against poly(lactic acid) (PLA) using forced assembly, where the PBSA layer thickness was about 60 nm. This unique technology allowed to process semicrystalline PBSA as confined polymer and amorphous PLA as confining polymer in a continuous manner. The continuity of PBSA layers within the 80/20 wt % PLA/PBSA layered films was clearly evidenced by atomic force microscopy (AFM). Similar thermal events to the reference films were revealed by thermal studies; indicating no diffusion of polymers during the melt-processing. Mechanical properties were measured for the multilayer film and the obtained results were those expected considering the fraction of each polymer, revealing the absence of delamination in the PLA/PBSA multinanolayer film. The confinement effect induced by PLA led to a slight orientation of the crystals, an increase of the rigid amorphous fraction (RAF) in PBSA with a densification of this fraction without changing film crystallinity. These structural changes allowed to strongly improve the water vapor and gas barrier properties of the PBSA layer into the multilayer film up to two decades in the case of CO2 gas. By confining the PBSA structure in very thin and continuous layers, it was then possible to improve the barrier performances of a biodegradable system and the resulting barrier properties were successfully correlated to the effect of confinement on the microstructure and the chain segment mobility of the amorphous phase. Such investigation on these multinanolayers of PLA/PBSA with the aim of evidencing relationships between microstructure implying RAF and barrier performances has never been performed yet. Besides, gas and water permeation results have shown that the barrier improvement obtained from the multilayer was mainly due to the reduction of solubility linked to the reduction of the free volume while the tortuosity effect, as usually expected, was not really observed. This work brings new insights in the field of physicochemical behaviors of new multilayer films made of biodegradable polyesters but also in interfacial processes due to the confinement effect induced in these multinanolayer structures obtained by the forced assembly coextrusion. This original coextrusion process was a very advantageous technique to produce eco-friendly materials with functional properties without the help of tie layer, additives, solvents, surface treatments, or inorganic fillers

Impact of water and thermal induced crystallizations in a PC/MXD6 multilayer film on barrier properties

A multilayer film composed of alternating layers of polycarbonate (PC) and poly(m-xylene adipamide) (MXD6) was elaborated by using an innovative multilayer coextrusion process. Quasi-continuous thin MXD6 layers (nanolayers) alternating with PC layers were successfully obtained. The PC/MXD6 multilayer film showed a confining effect of MXD6 exerted by PC layers leading to an improvement of barrier properties despite a low degree of crystallinity (X c < 10 wt%). In order to further improve the barrier performances, crystallization treatments induced by water and by heating were then applied on the multilayer film and allowed reaching around 30 wt% of crystallinity in MXD6 layers. To decouple crystallization and geometrical constraint effects on the barrier properties in the multilayer films, the two treatments were also applied on MXD6 films. Surprisingly, despite an increase of the degree of crystallinity from 6 to 26%, water crystallization did not permit to improve gas barrier performances of the MXD6 film nor into the PC/MXD6 multilayer film. On the other hand, thermal crystallization of MXD6 in the multilayer film seems to be a more efficient route to strongly decrease the gas and moisture permeability, up to 75% for nitrogen, 58% for oxygen, 84% for carbon dioxide and 43% for water

Structural and Barrier Properties of Compatibilized PE/PA6 Multinanolayer Films

The barrier performance and structural lightening of organic materials are increasingly desired and constitute a major challenge for manufacturers, particularly for transport and packaging. A promising technique which tends to emerge in recent years is that of multinanolayer coextrusion. The advantage is that it can produce multilayers made of thousands of very thin layers, leading to new properties due to crystalline morphology changes induced by confinement. This paper is focusing on the study of multinanolayered films with alternated polyethylene (PE), compatibilizer (PEgMA) and polyamide 6 (PA6) layers and made by a forced assembly coextrusion process equipped with layer multiplying elements (LME). PE/PA6 multilayer films consisting of 5 to 2049 layers (respectively 0 to 9 LME) were successfully obtained with well-organized multilayered structure. The evolution of the morphology and the microstructure of these two semi-crystalline polymers, when the thickness of each polymer layer decreases from micro-scale to nano-scale, was correlated to the water and gas transport properties of the PE/PA multilayers. The expected improvement of barrier properties was limited due to the on-edge orientation of crystals in very thin PE and PA6 layers. Despite this change of crystalline morphology, a slight improvement of the gas barrier properties was shown by comparing experimental results with permeabilities predicted on the basis of a serial model developed by considering a PE/PA6 interphase. This interphase observed by TEM images and the on-edge crystal orientation in multilayers were evidenced from mechanical properties showing an increase of the stiffness and the strength

ScenaLand: a simple methodology for developing land use and management scenarios

Scenarios serve science by testing the sensitivity of a system and/or society to adapt to the future. In this study, we present a new land use scenario methodology called ScenaLand. This methodology aims to develop plausible and contrasting land use and management (LUM) scenarios, useful to explore how LUM (e.g. soil and water conservation techniques) may afect ecosystem services under global change in a wide range of environments. ScenaLand is a method for constructing narrative and spatially explicit land use scenarios that are useful for end-users and impact modellers. This method is innovative because it merges literature and expert knowledge, and its low data requirement makes it easy to be implemented in the context of inter-site comparison, including global change projections. ScenaLand was developed and tested on six diferent Mediterranean agroecological and socioeconomic contexts during the MASCC research project (Mediterranean agricultural soil conservation under global change). The method frst highlights the socioeconomic trends of each study site including emerging trends such as new government laws, LUM techniques through a qualitative survey addressed to local experts. Then, the method includes a ranking of driving factors, a matrix about land use evolution, and soil and water conservation techniques. ScenaLand also includes a framework to develop narratives along with two priority axes (contextualized to environmental protection vs. land productivity in this study). In the context of this research project, four contrasting scenarios are proposed: S1 (business-as-usual), S2 (market-oriented), S3 (environmental protection), and S4 (sustainable). Land use maps are then built with the creation of LUM allocation rules based on agroecological zoning. ScenaLand resulted in a robust and easy method to apply with the creation of 24 contrasted scenarios. These scenarios come not only with narratives but also with spatially explicit maps that are potentially used by impact modellers and other endusers. The last part of our study discusses the way the method can be implemented including a comparison between sites and the possibilities to implement ScenaLand in other contexts.info:eu-repo/semantics/publishedVersio

Landscape design for soil conservation under land use and climate change

International audienceSoils and landscapes evolve simultaneously. Soil evolution is controlled by redistribution and transformation processes influenced by topographic and climatic parameters, with also a major contribution of management strategies. The perennial landscape features have a strong influence on soil spatial distribution (geometry) and soil genesis. Building landscapes which enhance soil resilience to degradation processes and increase soil services appears as a promising way to adapt to forthcoming climatic and land use evolutions. The presentation aims to synthetize major results from a research program nicknamed Landsoil which focused on the evolution of agricultural soils over medium time scales (decades to centuries) in relation to changing conditions of land use and climate. Precise study of the soil 3D organization in three contrasted landscapes (Brittany, Touraine, Languedoc-Roussillon) enabled to link soil redistribution in space to landscape components (field geometry, hedges or ditches network) and their past evolution. A dynamic and high resolution spatial modeling approach was developed coupling erosion processes and soil organic matter evolution and was calibrated over past evolution using dating techniques (Cs137, C14, OSL). The resulting Landsoil model was afterwards applied in a prospective manner under different scenarios of land use and climate change over the 21th century. Indicators of soil vulnerability and soil resilience were defined and tested by the comparison of several prospective scenarios applied on a same landscape and by comparison of the contrasted landscapes

Effet du réseau bocager sur l'organisation des sols. Redistributions des sols et stockage en carbone organique

The effect of hedgerow network on soil organisation at landscape scale is still unclear as most studies have been done in 2D, focusing on situations with hedges perpendicular to the steepest slope. Therefore, extrapolation at the whole landscape induces a wrong estimation of the hedgerow network effect at the landscape scale.Aims of this study were to understand and quantify at landscape scale, the effect of the hedgerow network on soil organisation and on associated soil organic carbon stocks, and to describe the dynamic of spatial processes responsible for these organisations.The adopted strategy has combined three complementary approaches. First a field study was carried out in an hedgerow network landscape historically documented, having contrasted topographical and landscape situations. This, in order to obtain a spatial characterisation of hedgerow networks which takes into account human activities and the three dimensional nature of the pedological cover at landscape scale.We combined relative dating approaches (analysis of historical documents and of soil geometry) and absolute dating techniques (14-Carbon, 137-Caesium), complementary to the spatial approaches. These techniques allowed us to date the organo-mineral horizons of the soil cover and to analyse the dynamic of processes responsible for modifications of the soil spatial organisation.Taking into account this temporal dimension was necessary to improve our comprehension of soil redistribution processes and to simulate in space and time the landscape evolution according to different soil use and management scenarios.L'effet du réseau bocager sur l'organisation des sols à l'échelle d'un paysage reste mal connu, car la majorité des études ont été menées en deux dimensions, en se limitant souvent à des contextes de talus perpendiculaires à la ligne de plus grande pente. L'extrapolation des résultats ainsi obtenus à l'ensemble du paysage, est de ce fait difficile et conduit à une mésestimation de l'impact du bocage sur les sols.Les objectifs de ce travail étaient de comprendre et de quantifier à l'échelle d'un paysage bocager, l'effet du système talus/haie sur l'organisation des sols et sur les stocks de carbone organique associés, ainsi que de décrire la dynamique des processus spatiaux qui ont conduit aux organisations observées.Pour y parvenir, la démarche adoptée a combiné trois approches complémentaires. Tout d'abord, nous avons conduit une étude de terrain dans un paysage bocager historiquement documenté et offrant des conditions topo-paysagères contrastées avec pour but une caractérisation spatiale de l'effet du réseau bocager qui prenne en compte l'action de l'homme et la nature tridimensionnelle de la couverture pédologique à l'échelle du paysage.Ensuite, nous avons couplé des approches de datation relative (analyse de documents historiques et géométrie des horizons) et absolue (carbone-14, césium-137), complémentaires des approches spatiales, pour dater les sols et analyser la dynamique des processus à l'origine des modifications de leurorganisation spatiale.Cette prise en compte de la dimension temporelle était nécessaire pour améliorer notre compréhension des processus de redistribution en sol et nous permettre d'engager une modélisation spatiale et temporelle simulant des évolutions du paysage bocager en fonction de différents scénarii d'occupation des sols