Flow instabilities of PP filled with crosslinked EPDM rubber : using rheology to understand and control its occurrence
department or school: Applied Science, Faculty of
department or school: Chemical and Biological Engineering, Department of
data provider: DSpace
degree campus: UBCV
creator: Ghahramani, Nikoo
issued: 2021-09-29T21:14:02Z
issued: 2021
related degree: Doctor of Philosophy - PhD
degree grantor: University of British Columbia
description: Thermoplastic vulcanizates (TPVs) are polymer blends that have good processability like their thermoplastic phase and good elasticity like their elastomeric phase. They consist of a high amount of dynamically cured rubber particles which make flow instability such as melt fracture intense and complicated. In this study a comprehensive rheological analysis is performed to gain a deep understanding of TPVs’ flow instabilities and identify the key parameters that control them. First, a thorough linear viscoelastic analysis is performed using several groups of TPVs which are systematically different in curing level, types of polymer components, and cured rubber content. All the TPVs show a non-terminal behavior reaching to an equilibrium modulus at low frequencies/high relaxation times. The equilibrium modulus, Gy, is an indication of the existence of yield stress and the linear modulus, G(t) can be modeled by a simple power-law model in the form of (𝐺(𝑡)−𝐺𝑦)∝𝑡−𝑝, where t is the time. A yield stress is also observed in the extensional tests and the relationship between extensional and shear yield stress is investigated. Due to the presence of oil and high amount of rubber particles, TPVs show wall slip. The multimode integral Kaye-Bernstein-Kearsley-Zapas (KBKZ) constitutive model considering wall slip is applied to study and model the TPVs’ non-linear behavior. To incorporate slip into the model, a new way is used by applying a fraction of imposed nominal strain to match the experimental data. Moreover, it is assumed that the material does not slip in the linear unyielding region i.e., for shear stresses less than the yield stress. Applying these assumptions, the KBKZ captures the experimental data well. Finally, to study processing parameters that affect the melt fracture phenomenon, capillary experiments are performed. It is observed that TPVs slip massively in capillary flow. Surface fracture of the TPVs gets better with shear rate indicating that the origin of melt…
aggregated CHO: https://circle.library.ubc.ca/rest/handle/2429/79810
note: Flow instabilities of PP filled with crosslinked EPDM rubber: using rheology to understand and control its occurrence by Nikoo Ghahramani B.Sc., Amirkabir University of Technology, Tehran, Iran, 2014 M.Sc., Amirkabir University of Technology, Tehran, Iran, 2017 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in THE FACULTY OF GRADUATE AND POSTDOCTORAL STUDIES (Chemical and Biological Engineering) THE UNIVERSITY OF BRITISH COLUMBIA (Vancouver) September 2021 © Nikoo Ghahramani, 2021 ii The following individuals certify that they have read, and recommend to the Faculty of Graduate and Postdoctoral Studies for acceptance, the dissertation entitled: Flow instabilities of PP filled with crosslinked EPDM rubber: using rheology to understand and control its occurrence submitted by Nikoo Ghahramani in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Chemical and Biological Engineering Examining Committee: Savvas G. Hatzikiriakos, Chemical and Biological Engineering, UBC Supervisor Mark Martinez, Chemical and Biological Engineering, UBC Supervisory Committee Member Jeffrey Giacomin, Chemical Engineering, Queen’s University External Examiner Simcha Srebnik, Chemical and Biological Engineering, UBC University Examiner Reza Vaziri, Civil Engineering, UBC University Examiner Additional Supervisory Committee Members: Sheldon Green, Mechanical Engineering, UBC Supervisory Committee Member Antonios Doufas, ExxonMobil Chemical Company Supervisory Committee Member Krishnan Iyer, ExxonMobil Chemical Company Supervisory Committee Member iii Abstract Thermoplastic vulcanizates (TPVs) are polymer blends that have good processability like their thermoplastic phase and good elasticity like their elastomeric phase. They consist of a high amount of dynamically cured rubber particles which make flow instability such as melt fracture intense and complicated. In this study a comprehensive rheological analysis …
has type: Thesis/Dissertation
date issued: 2021-11
is shown at: 10.14288/1.0402349
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
contributor: Hatzikiriakos, Savvas Georgios, 1961-
type: Text
identifier URI: http://hdl.handle.net/2429/79810