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Biodegradable Blends of Polycaprolactone with Thermoplastic Starch

Gang Li

Ph.D. thesis (2010)

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Abstract

This work presents an approach to preparing polycaprolactone (PCL)/thermoplastic starch (TPS) blends via a one-step extrusion approach. The one-step melt processing of polymer blends with thermoplastic starch is a complex operation involving plasticization, devolatilization, melt-melt mixing and morphology control. All this must be achieved within a maximum two minutes total residence time in an extruder. In addition, starch is a complex natural polymer and thus gelatinization is a delicate process. In order to determine the time/temperature boundaries ultimately required for the successful plasticization of starch in a polymer melt processing environment, differential scanning calorimetry (DSC), optical microscopy and wide angle X-ray diffraction (WAXD) were used to examine the critical aspects of starch gelatinization in glycerol/excess water mixtures. Simultaneously, these results were related to the morphology of melt-blended thermoplastic starch (TPS) in polycaprolactone (PCL). Secondly, the morphology development and interfacial interactions in PCL/TPS blends were studied. Finally, the biodegradation of native starch, thermoplastic starch (TPS) containing high concentration of glycerol, and its blends with low-density polyethylene (LDPE) and polylactic acid (PLA) were demonstrated under compost conditions. In the first part of the work, starch gelatinization was examined in detail. The onset and conclusion temperatures for wheat starch gelatinization were obtained via differential scanning calorimetry (DSC), X-ray diffraction and polarized light microscopy. The results indicate that water and glycerol exhibit significantly different effects on the starch gelatinization temperature. With a constant concentration of glycerol related to dry starch, the onset, To, peak, Tp,and conclusion, Tc, gelatinization temperatures all shift to low temperatures with increasing water concentration. Conversely, these gelatinization temperatures shift to high temperatures when the water concentration is held constant and the quantity of glycerol is increased. In both cases, the gelatinization endotherm becomes more pronounced with increasing plasticizer concentration in the system. These results are very useful to set up the extrusion temperatures since the gelatinization temperature can be changed by varying the ratio of water and glycerol in initial starch/water/glycerol mixtures.

Résumé

Ce travail présente une approche pour la préparation de mélanges polycaprolactone (PCL)/amidon thermoplastique (TPS) par extrusion en une seule étape. La mise en oeuvre en une étape à l'état fondu de mélanges polymères à base d'amidon thermoplastique est une opération complexe impliquant la plastification, la dévolatilisation, le mélange à l'état fondu et le contrôle de la morphologie. Tout ceci doit être complété en un temps de résidence total d'au plus deux minutes dans une extrudeuse. Afin de déterminer les limites de temps/température requises pour plastifier avec succès l'amidon dans un environnement de mise en oeuvre de polymères à l'état fondu, la calorimétrie par balayage différentiel (DSC), la microscopie optique et la diffraction de rayons X à grand angle (WAXS) ont été utilisées pour étudier les aspects clés de la gélification de l'amidon dans des mélanges glycérol/eau en excès. En même temps, ces résultats ont été liés à la morphologie de mélanges à l'état fondu d'amidon thermoplastique (TPS) et de polycaprolactone (PCL). Dans un deuxième temps, le développement de la morphologie et les interactions interfaciales dans les mélanges PCL/TPS ont été étudiés. Finalement, la biodégradation d'amidon natif, d'amidon thermoplastique (TPS) à haute teneur en glycérol, et de leurs mélanges avec du polyéthylène à basse densité (LDPE) et du poly(acide lactique) (PLA) a été démontrée sous des conditions de compostage.

Department: Department of Chemical Engineering
Program: Génie chimique
Academic/Research Directors: Basil D. Favis
PolyPublie URL: https://publications.polymtl.ca/258/
Institution: École Polytechnique de Montréal
Date Deposited: 23 Jun 2010 15:21
Last Modified: 25 Sep 2024 15:18
Cite in APA 7: Li, G. (2010). Biodegradable Blends of Polycaprolactone with Thermoplastic Starch [Ph.D. thesis, École Polytechnique de Montréal]. PolyPublie. https://publications.polymtl.ca/258/

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