Abstract
This work investigated the sorption and the diffusion properties of CO2 under high pressure and the further modificationsinduced in Poly(lactic acid) (PLA) thin layers. Poly(ethylene terephtalate) (PET) was also considered for comparativepurposes. Firstly, from thermodynamic equilibrium, the CO2 sorption isotherm (two sorption-desorption cycles, up to25 bar, at 25 °C) gave strong evidence of a physisorption mechanism and of a hysteresis phenomenon. Infrared spectroscopyanalysis confirmed that no chemical reaction occurred. Secondly, from the kinetics aspect, the CO2 diffusion coefficient wasfound around 10–13 m2·s–1 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 plasticizationreduced the glass transition temperature of PLA and accelerated the physical ageing of the polymer. These results are thereforeof significant importance in industrial processing and applications which involve close contact between CO2 and PLA.
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