This study focused on the development and analysis of polymeric films based on polylactic acid (PLA), combined with mineral additives and additional polymer phases, to enhance the gas barrier properties of PLA. Specifically, the effectiveness of using calcium carbonate obtained from ground eggshells and a secondary polymer phase composed of commercial aromatic biopolyesters was evaluated. The aim was to investigate the improvement of PLA’s barrier properties against oxygen and carbon dioxide through the selection of sustainable or waste-derived materials, seeking to enhance or at least not negatively affect the mechanical properties of the base material. This combination of characteristics is crucial for the development of sustainable materials intended for modified atmosphere packaging. To this end, several blends and biocomposites were developed, varying the composition and dispersion strategy of the fillers through a melt-mixing process using compression molding, and were characterized through thermal and physical analyses. Tensile tests were performed to assess the impact of the mineral fillers and the secondary polymer phase on the mechanical properties of the resulting films. Finally, the gas permeability of the films was measured to evaluate their barrier performance against oxygen and carbon dioxide in comparison to pure PLA, and the results were analyzed using the "solution-diffusion" model to assess the impact of the selected strategies. The results showed that the gas barrier properties in the blends and biocomposites did not improve significantly, with a deterioration in carbon dioxide permeability. Mechanical tests revealed that the addition of PBST and PBAT reduced the elastic modulus and increased the percentage elongation, while the addition of calcium carbonate fillers did not significantly affect the mechanical properties compared to pure PLA. The dispersion of the fillers was good; however, despite this, the barrier properties of the produced biocomposites did not improve.
Il presente studio si è concentrato sullo sviluppo e l’analisi di film polimerici a base di acido polilattico (PLA), combinati con additivi minerali e fasi polimeriche aggiuntive, per migliorare le proprietà barriera del PLA ai gas. In particolare, è stata valutata l’efficacia dell’uso di carbonato di calcio ottenuto da gusci d’uovo macinati e di una fase polimerica secondaria costituita da biopoliesteri aromatici commerciali. L’obiettivo è stato quello di ricercare il miglioramento delle proprietà barriera del PLA ad ossigeno e anidride carbonica attraverso la selezione di materiali sostenibili o di scarto, cercando di migliorare o senza alterare negativamente le proprietà meccaniche del materiale di base. Questo insieme di caratteristiche risulta fondamentale per lo sviluppo di materiali sostenibili destinati al confezionamento in atmosfera modificata. A tal fine sono stati sviluppati diversi blend e biocompositi, variando la composizione e la strategia di dispersione dei riempitivi attraverso una procedura di miscelazione a fusione mediante stampaggio a compressione e caratterizzati attraverso analisi termiche e fisiche. Sono stati eseguiti test di trazione per valutare l’impatto dei riempitivi minerali e della fase polimerica secondaria sulle proprietà meccaniche dei film risultanti. Infine, è stata misurata la permeabilità ai gas dei film per valutare le prestazioni barriera nei confronti di ossigeno e anidride carbonica rispetto al PLA puro e i risultati sono stati analizzati utilizzando il modello “solution-diffusion” per valutare l’impatto delle strategie selezionate. I risultati hanno mostrato che le proprietà barriera ai gas nei blend e nei biocompositi non sono migliorate significativamente, con un peggioramento della permeabilità dell’anidride carbonica. I test meccanici hanno rivelato che l’aggiunta di PBST e PBAT riduce il modulo elastico e aumenta l’allungamento percentuale, mentre l’aggiunta delle cariche di carbonato di calcio non influisce significativamente sulle proprietà meccaniche rispetto al PLA puro. La dispersione delle cariche è risultata buona, ma, nonostante ciò, le proprietà barriera dei biocompositi prodotti non sono migliorate.
Indagine sperimentale sul miglioramento delle proprietà barriera di PLA mediante lo sviluppo di biocompositi a base di carbonato di calcio da gusci d’uovo e blending con biopoliesteri
SARZO, SELENE
2023/2024
Abstract
This study focused on the development and analysis of polymeric films based on polylactic acid (PLA), combined with mineral additives and additional polymer phases, to enhance the gas barrier properties of PLA. Specifically, the effectiveness of using calcium carbonate obtained from ground eggshells and a secondary polymer phase composed of commercial aromatic biopolyesters was evaluated. The aim was to investigate the improvement of PLA’s barrier properties against oxygen and carbon dioxide through the selection of sustainable or waste-derived materials, seeking to enhance or at least not negatively affect the mechanical properties of the base material. This combination of characteristics is crucial for the development of sustainable materials intended for modified atmosphere packaging. To this end, several blends and biocomposites were developed, varying the composition and dispersion strategy of the fillers through a melt-mixing process using compression molding, and were characterized through thermal and physical analyses. Tensile tests were performed to assess the impact of the mineral fillers and the secondary polymer phase on the mechanical properties of the resulting films. Finally, the gas permeability of the films was measured to evaluate their barrier performance against oxygen and carbon dioxide in comparison to pure PLA, and the results were analyzed using the "solution-diffusion" model to assess the impact of the selected strategies. The results showed that the gas barrier properties in the blends and biocomposites did not improve significantly, with a deterioration in carbon dioxide permeability. Mechanical tests revealed that the addition of PBST and PBAT reduced the elastic modulus and increased the percentage elongation, while the addition of calcium carbonate fillers did not significantly affect the mechanical properties compared to pure PLA. The dispersion of the fillers was good; however, despite this, the barrier properties of the produced biocomposites did not improve.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.12608/73227