Flow-induced crystallization of polylactides in capillary flow
department or school: Applied Science, Faculty of
department or school: Chemical and Biological Engineering, Department of
data provider: DSpace
degree campus: UBCV
creator: Zhang, Ziyue
issued: 2021-04-21T19:22:53Z
issued: 2021
related degree: Master of Applied Science - MASc
degree grantor: University of British Columbia
description: Polylactide (PLA) is a biodegradable thermoplastic polyester produced from renewable biomass sources. The low crystallinity and the low associated crystallization kinetics have a negative impact on its mechanical and barrier properties. In this Master thesis, the effect of flow on the PLA crystallization is studied. The flow-induced crystallization (FIC) of two PLA with different microstructures (different L-lactic acid content) is studied using simple shear, uniaxial extension and capillary flow experiments. In simple shear and capillary flow, increase in shear rate and decrease in temperature was found to enhance the crystallization kinetics particularly for Weissenberg numbers (based on the reptation relaxation time, Wi) greater than 1. On the other hand, in uniaxial extensional flow, once a critical Hencky strain is achieved, crystallization starts independently of strain rate and temperature. The amount of mechanical work per unit volume imposed/dissipated onto the polymers during flow to initialize crystallization was also calculated in capillary flow. The critical mechanical work for the onset of flow-induced crystallization was found to be independent of temperature and degree of molecular chain stretch (Wi) as Wi becomes greater than 1. Lastly, the PLA sample with higher content of PLLA showed slightly higher zero-shear viscosity and a smaller thermodynamic barrier for the onset of crystallization.
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/77856
note: Flow-induced crystallization of polylactides in capillary flow by Ziyue Zhang B.A.Sc, The University of British Columbia, 2019 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF APPLIED SCIENCE in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Chemical and Biological Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) April 2021 © Ziyue Zhang, 2021 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, the thesis entitled: Flow-induced crystallization of polylactides in capillary flow submitted by Ziyue Zhang in partial fulfillment of the requirements for the degree of Master of Applied Science in Chemical and Biological Engineering Examining Committee: Dr. Savvas G. Hatzikiriakos, Chemical and Biological Engineering, UBC Supervisor E. Johan Foster, Chemical and Biological Engineering, UBC Supervisory Committee Member Dana Grecov, Mechanical Engineering, UBC Supervisory Committee Member iii Abstract Polylactide (PLA) is a biodegradable thermoplastic polyester produced from renewable biomass sources. The low crystallinity and the low associated crystallization kinetics have a negative impact on its mechanical and barrier properties. In this Master thesis, the effect of flow on the PLA crystallization is studied. The flow-induced crystallization (FIC) of two PLA with different microstructures (different L-lactic acid content) is studied using simple shear, uniaxial extension and capillary flow experiments. In simple shear and capillary flow, increase in shear rate and decrease in temperature was found to enhance the crystallization kinetics particularly for Weissenberg numbers (based on the reptation relaxation time, Wi) greater than 1. On the other hand, in uniaxial extensional flow, once a critical Hencky strain is achieved, crystallization starts independently of strain rate and temperature. The amount of mechanical work per unit vo…
has type: Thesis/Dissertation
date issued: 2021-05
is shown at: 10.14288/1.0396885
language: eng
degree discipline: Chemical and Biological Engineering
provider: Vancouver : University of British Columbia Library
publisher: University of British Columbia
rights: Attribution-NonCommercial-NoDerivatives 4.0 International
rights URI: http://creativecommons.org/licenses/by-nc-nd/4.0/
scholar level: Graduate
type: Text
identifier URI: http://hdl.handle.net/2429/77856