Longo, Alessandra (2022) Interplay between crystals and bubbles in PLLA. [Tesi di dottorato]
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| Tipologia del documento: | Tesi di dottorato |
|---|---|
| Lingua: | English |
| Titolo: | Interplay between crystals and bubbles in PLLA |
| Autori: | Autore Email Longo, Alessandra alessandra.longo@unina.it |
| Data: | 10 Marzo 2022 |
| Numero di pagine: | 102 |
| Istituzione: | Università degli Studi di Napoli Federico II |
| Dipartimento: | Ingegneria Chimica, dei Materiali e della Produzione Industrialea |
| Dottorato: | Ingegneria dei prodotti e dei processi industriali |
| Ciclo di dottorato: | 34 |
| Coordinatore del Corso di dottorato: | nome email D'Anna, Andrea anddanna@unina.it |
| Tutor: | nome email Di Maio, Ernesto [non definito] Di Lorenzo, Maria Laura [non definito] |
| Data: | 10 Marzo 2022 |
| Numero di pagine: | 102 |
| Parole chiave: | Poly(l-lactic acid), polymeric foams, thermal properties, crystallization kinetic, homogeneous crystal nuclei, CO2 induced mesophase |
| Settori scientifico-disciplinari del MIUR: | Area 09 - Ingegneria industriale e dell'informazione > ING-IND/22 - Scienza e tecnologia dei materiali |
| Depositato il: | 17 Mar 2022 12:41 |
| Ultima modifica: | 28 Feb 2024 10:47 |
| URI: | http://www.fedoa.unina.it/id/eprint/14452 |
Abstract
The present thesis focuses on the study of the relationship between the thermal properties of poly (l-lactic acid) (PLLA) and its foaming behavior. Three methodologies to tune both thermal properties and foam morphology preserving the purity and homogeneity of the material, i.e., without the addition of external agents, are presented. In order to enhance crystallization rate of PLLA, a structural modification of the polymer chain, by addition of side chains of the same chemistry, has been attempted to obtain a branched structure where fast-crystallizing short branches can favor overall crystallization. To fine tune foam morphology and increase the expansion ratio, experiments of foaming glassy PLLA annealed for various times have been conducted demonstrating, for the first time, that homogeneous crystal nuclei can successfully promote not only the known crystal nucleation, but also nucleation of bubbles, thus allowing to increase expansion ratio and tune foam morphology. With the gained knowledge on interplay between crystals and gas in PLLA foaming, the final part of the research has been dedicated to the effect of CO2 on chain reorganization of the polymer. At low temperature (around room temperature), CO2 can induce formation of a metastable mesophase, named alpha"-form that, upon further heating, transforms to stable alpha-crystals. The kinetics of formation CO2-induced mesophase was studied in a PLLA containing homogeneous crystal nuclei, then non-isothermal crystallization of PLLA containing both homogeneous crystal nuclei and mesophase has been investigated.
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