How high pressure CO2 impacts PLA film properties

This work investigated the sorption and the diffusion properties of CO2 under high pressure and the further modifications induced in Poly (lactic acid) (PLA) thin layers. Poly (ethylene terephtalate) (PET) was also considered for comparative purposes. Firstly, from thermodynamic equilibrium, the CO2 sorption isotherm (two sorption-desorption cycles, up to 25 bar, at 25\ub0C) gave strong evidence of a physisorption mechanism and of a hysteresis phenomenon. Infrared spectroscopy analysis confirmed that no chemical reaction occurred. Secondly, from the kinetics aspect, the CO2 diffusion coefficient was found around 10\u201313 m2\ub7s\u20131 and was slightly faster for sorption compared to desorption. Additionally, when CO2 sorption occurred, the PLA structure and its functional properties were modified due to plasticization and swelling. CO2 plasticization reduced the glass transition temperature of PLA and accelerated the physical ageing of the polymer. These results are therefore of significant importance in industrial processing and applications which involve close contact between CO2 and PLA

Wine aging: a bottleneck story

International audienceThe sporadic oxidation of white wines remains an open question, making wine shelf life a subjective debate. Through a multidisciplinary synoptic approach performed as a remarkable case study on aged bottles of white wine, this work unraveled a yet unexplored route for uncontrolled oxidation. By combining sensory evaluation, chemical and metabolomics analyses of the wine, and investigating oxygen transfer through the bottleneck/stopper, this work elucidates the importance of the glass/cork interface. It shows unambiguously that the transfer of oxygen at the interface between the cork stopper and the glass bottleneck must be considered a potentially significant contributor to oxidation state during the bottle aging, leading to a notable modification of a wine's chemical signature