Longo, Alessandra (2022) Interplay between crystals and bubbles in PLLA. [Tesi di dottorato]


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Item Type: Tesi di dottorato
Resource language: English
Title: Interplay between crystals and bubbles in PLLA
Longo, Alessandraalessandra.longo@unina.it
Date: 10 March 2022
Number of Pages: 102
Institution: Università degli Studi di Napoli Federico II
Department: 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:
D'Anna, Andreaanddanna@unina.it
Di Lorenzo, Maria LauraUNSPECIFIED
Date: 10 March 2022
Number of Pages: 102
Keywords: 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
Date Deposited: 17 Mar 2022 12:41
Last Modified: 28 Feb 2024 10:47
URI: http://www.fedoa.unina.it/id/eprint/14452

Collection description

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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