Thermoplastic polyurethanes (TPUs) constitute a very versatile class of polymeric materials that find applications in a variety of fields, from automotive to sport system. This versatility is due to the particular nature of its microstructure, given by the co-presence of rigid and flexible domains that tend to spontaneously segregate due to thermodynamic incompatibility. This allows a combination of high flexibility, toughness and high physical performance of the material. It is known, however, that the processing of such materials significantly affects the stability of the microstructure and physical performance, only achievable after a post-processing curing. The following thesis work investigates the relationship between the processing conditions of commercial TPUs and the maturation process of their mechanical performance over time. For this purpose, two types of TPUs, an ether-based and ester-based ones, were analyzed; the materials were processed by injection molding and compression molding in order to compare their effects on the material. The evolution of the material's microstructure over time was analyzed by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC), while mechanical performance was quantified by measurements of flexural stiffness and impact strength at low temperature. The evolution of microstructure and properties was studied over time and at different storage temperatures, evaluating their influence on the kinetics of microstructure stabilization. These results were compared with a high-temperature heat treatment process, usually conducted in order to accelerate the curing process, in order to understand the most influencing factors on the final performance of such materials.
I poliuretani termoplastici (TPU) costituiscono una classe di materiali polimerici molto versatili che trova applicazioni in diversi settori, dall’automotive fino allo sport system. Tale versatilità è attribuibile alla particolare natura della sua microstruttura, data dalla compresenza di domini rigidi e domini flessibili che tendono a segregarsi spontaneamente a causa di incompatibilità termodinamica. Ciò permette di combinare elevata flessibilità, tenacità ed alte prestazioni fisiche del materiale. Risulta tuttavia noto che il processing di tali materiali influenzi significativamente la stabilità della microstruttura e delle prestazioni fisiche, stabilità che risulta ottenibile solamente in seguito ad un processo di maturazione successivo alla lavorazione. Con il seguente lavoro di tesi si è quindi approfondita la relazione tra le condizioni di lavorazione di TPU commerciali e il processo di maturazione delle loro performance meccaniche nel tempo. A tal fine sono stati analizzate due tipologie di TPU, a base etere e a base estere; i materiali sono stati trasformati tramite stampaggio ad iniezione e stampaggio a compressione per comparare gli effetti generati dal processing sul materiale. L’evoluzione della microstruttura del materiale nel tempo è stata analizzata mediante spettroscopia infrarossa in trasformata di Fourier (FT-IR) e calorimetria a scansione differenziale (DSC), mentre le prestazioni meccaniche sono state quantificate con misurazioni di rigidità flessione e resistenza all’urto a bassa temperatura. L’evoluzione di microstruttura e proprietà è stata studiata nel tempo e a diverse condizioni di temperatura di stoccaggio, valutandone l’influenza sulla cinetica di stabilizzazione della microstruttura. Tali risultati sono stati comparati con un processo di trattamento termico ad alta temperatura, usualmente condotto al fine di accelerare il processo di maturazione, per comprendere i fattori maggiormente influenzanti le prestazioni finali di tali materiali.
Analisi del fenomeno di maturazione di poliuretano termoplastico a seguito di processing e trattamento termico
SOFI, VIVIANA
2022/2023
Abstract
Thermoplastic polyurethanes (TPUs) constitute a very versatile class of polymeric materials that find applications in a variety of fields, from automotive to sport system. This versatility is due to the particular nature of its microstructure, given by the co-presence of rigid and flexible domains that tend to spontaneously segregate due to thermodynamic incompatibility. This allows a combination of high flexibility, toughness and high physical performance of the material. It is known, however, that the processing of such materials significantly affects the stability of the microstructure and physical performance, only achievable after a post-processing curing. The following thesis work investigates the relationship between the processing conditions of commercial TPUs and the maturation process of their mechanical performance over time. For this purpose, two types of TPUs, an ether-based and ester-based ones, were analyzed; the materials were processed by injection molding and compression molding in order to compare their effects on the material. The evolution of the material's microstructure over time was analyzed by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC), while mechanical performance was quantified by measurements of flexural stiffness and impact strength at low temperature. The evolution of microstructure and properties was studied over time and at different storage temperatures, evaluating their influence on the kinetics of microstructure stabilization. These results were compared with a high-temperature heat treatment process, usually conducted in order to accelerate the curing process, in order to understand the most influencing factors on the final performance of such materials.File | Dimensione | Formato | |
---|---|---|---|
SOFI_VIVIANA.pdf
accesso riservato
Dimensione
8.77 MB
Formato
Adobe PDF
|
8.77 MB | Adobe PDF |
The text of this website © Università degli studi di Padova. Full Text are published under a non-exclusive license. Metadata are under a CC0 License
https://hdl.handle.net/20.500.12608/58619