Oxidative degradation of polylactide (PLA) and its effects on physical and mechanical properties

The thermo-oxidative degradation of polylactide (PLA) films was studied between 70 and 150 C. It was shown that the oxidative degradation of PLA leads to a random chain cission responsible for a reduction of the molar mass. These molar mass changes affect Tg and the degree of crystallinity, and it was found that Tg decreases according to the Fox–Flory theory whereas the degree of crystallinity increases due to a chemicrystallization process. A correlation between molar mass and strain at break during oxidation has been established: PLA displays a brittle behavior when Mn falls below 40 kg mol 1 in agreement with relationships linking the critical value for embrittlement with the molar mass between entanglements

Solubility factors as screening tools of biodegradable toughening agents of polylactide

Changes in the thermomechanical properties of polylactide (PLA) plasticized by two biodegradable and biobased molecules, Polysorb ID37 (PID37) and squalene, were compared to formulations with petroleum-based plasticizers, namely, acetyl tributyl citrate, poly(ethylene glycol) 400, and dioctyl adipate (DOA). The solubility parameters of the additives were calculated and were related to the plasticization behaviors. PID37 proved to be miscible with PLA because of its polar functions and short alkyl groups. It decreased the PLA glass-transition temperature (Tg) and increased in ductility when Tg approached room temperature. Squalene had a low miscibility because of the absence of polar groups. Tg was not depressed. Ductility improvements were nevertheless reached because the immiscible inclusions efficiently induced crazing by the distribution of stress concentration points all over the material; this delayed failure. The maximum elongations at break were 60% for squalene, 400% for DOA, and 500% for PID37. The solubility factors were, thus, an efficient prediction tool for the plasticizing behavio

Physical aging and its effect on mechanical properties of toughened PLA films

Physical aging plays an important role in determining the long terms performance of polymers, especially PLA, whose Tg is close to ambient temperature. Considering long term performances, PLA/PHBV/PODC blends are the most promising materials for the toughening of PLA. Indeed, for these blends significant improvement in the strain at break was observed, along with a limited depression of the Young modulus and the stress at yield in comparison to neat PLA, as well as animproved thermal stability

Industrial vegetable oil by-products increase the ductility of polylactide

The use of industrial by-products of the vegetable oil industry as ductility increasing additives of polylactide (PLA) was investigated. Vegetable oil deodorization condensates were melt-blended by twin-screw extrusion up to a max- imum inclusion quantity of 20 wt% without preliminary purification. Sample films were obtained by single screw cast extrusion. Compounded PLA films featured largely improved ductility in tensile testing with an elongation at break up to 180%. The glass transition temperature remained higher than room temperature. The native mixture of molecules, which composed the deodorization condensates, had superior performance compared to a synthetic mixture of main compounds. The investigation of the correlation between composition of the additives and the ductility of the PLA blends by Principal Component Analysis showed synergy in property improvement between fatty acids having a melting point below and beyond the room temperature. Furthermore, a compatibilizing effect of molecules present in the native mixture was evi- denced. Oil deodorization condensates, which are a price competitive by-product of the vegetable oil industry, are therefore a very promising biobased and biodegradable additive for improving the ductility of PLA

Palm oil deodorizer distillate as toughening agent in polylactide packaging films

A used-as-shipped biobased and biodegradable by-product of the palm oil refining increases polylactide (PLA) elongation at break up to 130% and allows film blowing without further additives. PLA blends are biodegradable and comply with legal norms of food contact materials. Polylactide (PLA) is the most used biodegradable and biobased food packaging polymer for rigid containers and films. However, its low ductility is a hurdle for increasing its applications in flexible food packaging. A solution is the use of additives. Palm oil deodorizer distillate (PODC) is revealed to be an excellent additive promoting PLA ductility. PODC is a by-product of vegetable oil refining, which is available in stable quality and in sufficient amounts. Amorphous PLA/PODC blends had an elongation at break of around 130% and that of semi-crystalline blends was still around 55% compared to the initial 5% of neat PLA. At the same time the PLA rigidity and high glass transition temperatures were kept. PODC was also a very efficient processing aid, allowing for film blow extrusion. The blends were stable in properties during six months without exudation. They complied with legal norms of Food Contact Materials (EU 10/2011) and induced no sensorial alteration of packed food. Therefore PODC is a very interesting alternative to common plasticizers for the production of flexible PLA packaging films

Rational design of a biobased and biodegradable film for food packaging application using formulation and process

L'utilisation de ressources renouvelables et la production de matériaux biodégradables sont des solutions adaptées afin de diminuer l'impact environnemental du secteur des plastiques. Il existe donc une demande du marché pour des produits écoresponsables, à condition que ces derniers soient techniquement et économiquement compétitifs par rapport aux matériaux classiquement utilisés. Dans le domaine de l'emballage alimentaire, une technique très employée permettant la réalisation de matériaux performants est la création de structures multicouches combinant avantageusement les propriétés de différents thermoplastiques. Néanmoins, de tels matériaux multi-matières sont difficilement recyclables, leur biodégradabilité devient alors une propriété pertinente. Cette étude propose la réalisation de films souples biosourcés et biodégradables pour l'emballage alimentaire, à partir du polylactide et de coproduits de l'huilerie en tant qu'additifs, notamment les condensats de désodorisation. Parmi ces derniers, la solubilité partielle de leurs molécules ainsi que l'effet synergique des constituants liquides et solides à température ambiante, en fonction de la longueur et du degré d'insaturation de leurs chaînes alkyles, ont été montrés comme responsables de l'augmentation de la ductilité du PLA, permettant néanmoins de conserver sa vitrosité à température ambiante et son intéressante rigidité. L'ajout de PHBV au PLA formulé avec les coproduits de l'huilerie a également été étudié, engendrant principalement une amélioration significative de la tenue thermomécanique du matériau. Des essais d'accroissement d'échelle comprenant la production de granulés, l'extrusion à plat de films ainsi que leur impression sur des machines industrielles ont été réalisés. Enfin, avec l'aide du Laboratoire National de Métrologie et d'Essais (LNE), la conformité du film développé avec les exigences légales concernant les matières thermoplastiques destinées au contact des aliments, mais également son aptitude à la biodégradation selon la norme EN 13432, ont été vérifiées.The use of renewable resources and the production of biodegradable materials are appropriate solutions to reduce the environmental impact of the sector of plastics. There is thus a demand for eco-friendly products on the market provided they obtain performance equal or superior to synthetic materials currently used. One possibility, widely used in the food sector, to achieve efficient packaging film is the creation of multilayer structures by combining advantageous properties of different plastics. In this case, recycling of materials is difficult and the biodegradability of the packaging becomes relevant. This study proposes designing biobased and biodegradable films for food packaging from polylactide and co- products of the oil mill industry as additives, in particular the deodorization condensates. Among these lasts, the partial solubility of their molecules and the synergetic effect of the liquid and solid fat components at room temperature, depending on their alkyl chain length and unsaturation ratio, have both been observed to be responsible for the ductility increase, while the higher than room temperature glass transition of PLA and its interesting rigidity were retained. Addition of PHBV to the formulated PLA with oil by-products has also been studied, mainly leading to a significant improvement in the thermomechanical resistance of the material. Scaled-up trials comprising the production of formulated pellets, cast extruded films and their printing using industrial devices were performed. Finally, with the help of the “Laboratoire National de Métrologie et d’Essais” (LNE), the compliance with requirements of Food Contact Material regulation of a formulated film of PLA, as well as its biodegradability according to the EN 13432 standard, have both been proved

Plasticization of poly(lactide)

External plasticization is a widely applied technique to improve PLA processability and toughness. Keys to successful plasticization of PLA are the miscibility of the plasticizer and its permanence in the polymer structure to ensure long-term stability of the material. To provide rules for successful plasticizing of PLA, a brief reminder of physicochemical mechanisms behind plasticization is given and the main theories allowing for the calculation of solubility parameters are summarized. To make use of this approach, a number of solubility parameters were gathered for potential PLA plasticizers. This chapter provides furthermore a comprehensive overview of literature results on glass transition temperatures and mechanical properties obtained for PLA and PLA nanocomposites mixed with monomeric and polymeric plasticizers. Additionally, physical and chemical long-term stability of plasticized materials is detailed. Finally, novel strategies of compounding PLA with additives derived from by-products of agriculture and food industries are discussed

Saprolite influence on formation of well-drained and hydromorphic horizons in an acid soil system as determined by structural analysis

International audienc

Pourquoi un referentiel pedologique?. Definition des horizons de reference

National audienc

Soldidac: un hypermedia educatif pour la decouverte de la couverture pedologique

National audienc