Abstract
The present work was aimed to study swelling kinetics of polylactic acid (PLA) and its impregnation with thymol in supercritical carbon dioxide (scCO2) medium. The influences of temperature and soaking time on the swelling kinetics and impregnation yield of PLA cylindrical disc and film were investigated. Swelling experiments were performed in a high pressure view cell at 10 MPa and temperatures of 40°C, 60°C and 75°C for 2 to 24 h. On the basis of swelling kinetics, pressure of 10 MPa and temperature of 40°C were chosen for supercritical solvent impregnation (SSI) of the PLA samples during 2 to24 h. The highest swelling extent was observed for the PLA monolith after 24 h treatment with pure scCO2 (7.5%) and scCO2 with thymol (118.3%). It was shown that sufficiently high amount of thymol can be loaded into both PLA monolith and film using SSI after only 2 h (10.0% and 6.6%, respectively). Monolith and film of PLA impregnated with thymol could be suitable for active food packaging and sterile medical disposables.
Highlights
One of the most important trends in the polymer field nowadays is replacement of petroleum-based polymers with bio-based ones
Longer soaking time led to the higher swelling extent of the polylactic acid (PLA) disc while the temperature increase resulted in decrease of the swelling extent
The highest swelling extent (7.45%) of the PLA disc at 10 MPa was recorded after 24 h and at the lowest temperature tested (40 °C)
Summary
One of the most important trends in the polymer field nowadays is replacement of petroleum-based polymers with bio-based ones. Polylactic acid (PLA) has been very attractive for food packaging and biomedical applications being biocompatible and biodegradable polymer with relatively low cost production and good physical and mechanical properties. Of lactide, the cyclic dimer of lactic acid [1, 2]. The ratio between the two stereoisomers, L-lactic acid and D-lactic acid, control the PLA properties, in particular crystallinity [2]. Crystalline level of the PLA modulates its permeability, mechanical performance, heat deflection temperature, and biodegradation rate. PLA has attracted interest as a packaging material. Its ability to slowly degrade in the human body makes it suitable for biomedical applications (e.g. tissue engineering scaffold) [1, 2]
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