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A Dissertation Entitled Acetaldehyde Scavengers for Poly(Ethylene Terephthalate)

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A Dissertation Entitled Acetaldehyde Scavengers for Poly(Ethylene Terephthalate) A Dissertation entitled Acetaldehyde Scavengers for Poly(ethylene terephthalate): Chemistry of Reactions, Capacity, and Modeling of Interactions by Brent A. Mrozinski Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Engineering Dr. Saleh A. Jabarin, Committee Chair Dr. Dong-Shik Kim, Committee Member Dr. Yong-Wah Kim, Committee Member Dr. Steven E. LeBlanc, Committee Member Dr. Arunan Nadarajah, Committee Member Dr. Patricia R. Komuniecki, Dean College of Graduate Studies The University of Toledo December 2010 Copyright 2010, Brent A. Mrozinski This document is copyrighted material. Under copyright law, no parts of this document may be reproduced without the expressed permission of the author. An Abstract of Acetaldehyde Scavengers for Poly(ethylene terephthalate): Chemistry of Reactions, Capacity, and Modeling of Interactions by Brent A. Mrozinski Submitted to the Graduate Faculty as partial fulfillment of the requirements for the Doctor of Philosophy Degree in Engineering The University of Toledo December 2010 During the melting and processing of poly(ethylene terephthalate) (PET), degradation of the material may occur. One of the more common degradation products is acetaldehyde (AA). Due to its low boiling point, 21oC, AA is able to diffuse out of PET and into either the atmosphere or the packaged contents of the PET container. The diffusion of AA into packaged contents is of concern, because many food products have a limited threshold for the sweet, fruity taste and odor of AA. One of the ways to limit the AA affects is through the addition of AA scavenging agents. While these additives do not limit the generation of AA; they are designed to interact with and reduce the amount of AA that can be release from PET articles. The purpose of this study was not only to study these AA and AA scavenger interactions and quantify their abilities in reducing AA concentrations in PET; it was also to develop an initial model to predict effectiveness of adding AA scavengers to multi-cavity PET injection molding systems. Through this work, it was determined that anthranilamide and meta-xylenediamine (MXDA) reduce AA concentrations in PET by means of a reaction mechanism. Alpha-cyclodextrin, however, scavenges AA through a hydrogen iii bonding/size-enclosing scheme. Regardless of the mechanism, it was proven that these three scavengers are capable of reducing detectable AA concentrations in PET. It was generally found that the greater the AA scavenger concentration, the great the effect. Additionally, the changes in the physical properties of PET due to AA scavenger addition were studied. It was shown that melt-blending these additives into PET could adversely affect the intrinsic viscosity (I.V.) and color of the PET blend resin and/or container. The thermal properties and oxygen permeation of PET were not affected by AA scavenger addition. The modification of an existing multi-cavity injection molding program was applied to account for the addition of AA scavengers, to PET resin, when predicting the accumulation of AA within PET preforms. The approach to modify this original program and methodologies to quantify the appropriate kinetic terms has been described in detail. Finally, the modified simulation program was then used to predict the effectiveness of various AA scavenger/PET blends in reducing detectable AA concentrations in PET preforms. While complete agreement between the modeling results and observed trends from single-cavity injection molding was not achieved, the groundwork was laid to make further improvements and advance predictability for future modeling programs. iv To my wife, Whitney, you are the most important part of my life and I hope that I show you the constant and unwavering love and support that you show me everyday. I look forward to our journey together and all the joy it may bring. To my mother, Nancy, thank you for too many things to list. Your love, guidance, and friendship throughout these first 29 years of my life have been unimaginable. Thank you for the tremendous examples of how to treat and respect others, how to be a parent, and how to be a loving and selfless spouse. To my late father, Richard, who was not only a parent to me; he was also my best friend. His tireless love, support, and encouragement still lives with me to this day. We shared many great moments together: going up north to cut firewood, playing catch, watching Detroit Tigers baseball games, and trying to teach him about golf; a sport for which he had no interest except for the fact that it was important to me. His sudden passing on December 19, 2006, following a short bout with cancer, left a tremendous void in my life and heart. We were always very close, but those last 3 months were filled with moments that I will never forget: many shared laughs, tears, and short walks through the house. To quote a song from Keith Urban, “I only hope when I have my own family that everyday I see a little more of my father in me.” Acknowledgments First and foremost, I would like to thank Dr. Saleh A. Jabarin for giving me this tremendous opportunity to learn from him and conduct this research project at the Polymer Institute, under his guidance. His knowledge, encouragement, and incredible patience have been not only appreciated, but greatly needed as well. I would like to thank Dr. Mike Cameron for his help with the computational modeling work and Mrs. Elizabeth Lofgren for her help with the various analytical experiments and for reviewing this work. The generosity of their time and effort has been immensely appreciated. Thank you to Mr. Mike Mumford for his help with the processing equipment and experiments and to Mrs. Jackie Zydorczyk for her support and help. Thank you to my fellow students at the Polymer Institute for your encouragement and suggestions throughout my project; especially to Mr. Thomas R. Matthews, Dr. Sung-Gi Kim, and Dr. Kamal Mahajan for their assistance in conducting experiments. Thank you, as well, to the PET Industrial Consortium for their financial support for this work. I would like to thank Dr. Dong-Shik Kim, Dr. Yong-Wah Kim, Dr. Steven E. LeBlanc, and Dr. Arunan Nadarajah for serving on my dissertation committee. A final thank you is extended to my wife, my mother, and my entire family for their support and encouragement throughout these years. vi Contents Abstract iii Acknowledgments vi Contents vii List of Figures xiii List of Tables xxi 1 Introduction 1 1.1 Poly(ethylene terephthalate) Overview .................................................................1 1.2 Synthesis of PET ...................................................................................................2 1.2.1 Melt-Phase Polymerization.........................................................................2 1.2.2 Solid-State Polymerization .........................................................................5 1.2.3 Direct Melt-Phase to Higher I.V.................................................................7 1.2.4 PET Copolymers.........................................................................................8 1.3 Degradation of PET...............................................................................................9 1.3.1 Hydrolytic Degradation of PET..................................................................9 1.3.2 Thermal Degradation of PET....................................................................10 1.3.3 Thermal-Oxidative Degradation of PET ..................................................10 1.4 Acetaldehyde in PET...........................................................................................11 1.4.1 Overview...................................................................................................11 vii 1.4.2 Amount of Acetaldehyde in PET..............................................................12 1.4.3 PET Degradation Routes That Generate Acetaldehyde............................13 1.4.3.1 Thermal Decomposition of Hydroxyl End-Groups....................14 1.4.3.2 Breakdown of Diethylene Glycol Molecules .............................14 1.4.3.3 Reactions with Vinyl Ester End-Groups ....................................15 1.4.3.4 Presence of Oxygen....................................................................16 1.4.3.5 Presence of DEG Linkages within PET Chains .........................17 1.4.3.6 Presence of Free Radicals ..........................................................19 1.4.4 Ways to Reduce the Amount of AA within PET......................................20 1.5 Rationale and Objectives.....................................................................................22 2 Literature Review 25 2.1 Minimizing AA During PET Degradation Mechanisms .....................................25 2.1.1 Limiting Thermal Degradation.................................................................25 2.1.2 Limiting Thermal-Oxidative Degradation................................................27 2.2 Minimizing AA by Choice of Polymerization Catalysts.....................................29 2.3 Minimizing AA by Choice of PET Resins..........................................................30 2.4 Minimizing AA by Means of Acetaldehyde (AA) Scavengers...........................31 2.4.1 Reactive AA Scavengers ..........................................................................31 2.4.1.1 Polyamides ..................................................................................31 2.4.1.2 Low Molecular
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