Poly L-lactic acid (PLLA) and Poly Methyl Methacrylate (PMMA) Blends and Their Interaction with C 02 at Sub- Critical Conditions By Baisheng Yao A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirement for the degree of Master of Science Carleton University Department of Chemistry 1125 Colonel By Drive Ottawa, Ontario, Canada June, 2007 © Copyright Baisheng Yao, 20007 Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 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The author retains copyright L'auteur conserve la propriete du droit d'auteur ownership and moral rights in et des droits moraux qui protege cette these. this thesis. Neither the thesis Ni la these ni des extraits substantiels de nor substantial extracts from it celle-ci ne doivent etre imprimes ou autrement may be printed or otherwise reproduits sans son autorisation. reproduced without the author's permission. In compliance with the Canadian Conformement a la loi canadienne Privacy Act some supporting sur la protection de la vie privee, forms may have been removed quelques formulaires secondaires from this thesis. ont ete enleves de cette these. While these forms may be included Bien que ces formulaires in the document page count, aient inclus dans la pagination, their removal does not represent il n'y aura aucun contenu manquant. any loss of content from the thesis. i * i Canada Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Abstract This work demonstrated the possibility of processing blends of poly L-lactic acid (PLLA) and poly methyl methacrylate (PMMA) with CO 2 through studying changes in the glass transition temperature, solubility, diffusivity and finally generated foam morphologies. One glass transition temperature, Heat-induced crystallization and C02-induced crystallization were observed in the samples. However, the addition of PMMA to PLLA reduced the rate of PLLA crystallization and increased the decomposition temperature. The solubility capacity for the blends was investigated. Analysis of the diffusion coefficients indicated them to be concentration dependent and therefore the possibility of existence of retrograde behavior in the blend-CC >2 system. The foam morphologies were strongly related to blend composition, foaming temperature, CO 2 saturation conditions as well as the CO2 induced crystallization and retrograde behavior in the system. A mathematical model was also implemented to predict CO2 solubility, blend swelling factors and glass transition behaviors in blend-CC >2 system. ii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Acknowledgements I am very glad to have had the opportunity to do my research and conduct my experimental work at the National Research Canada under the supervision of Dr. Victoria Nawaby. I thank her for her support, encouragement and sound advice. Her valuable questions, comments and suggestions eventually enabled me to grasp rich complexity and increased the value of this research greatly. I would also like to express my most sincere thanks to Dr. Bob Burk and Dr. Liao Xia, Steve Liu, David Kinston, Gill Roberson and Dr. Pam Whitfield for their kind assistance in my research. I wish to thank my entire extended families for providing a loving environment, understanding and support during the two years. My wife Chunqi Ma, my son Martin Yao, my mother-in-law Guilan Li and my father-in-law Shangzhi Ma were particularly supportive. Finally I thank Carleton University for a Graduate Scholarship which gave me two years of financial support. iii Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. Table of Contents Abstract .....................................................................................................................................ii Acknowledgements ............................................................................................................... iii Table of Contents ...................................................................................................................iv List of Tables ........................................................................................................................viii List of Figures ......................................................................................................................... ix Chapter 1: Introduction ........................................................................................................1 1.1 Biopolymers................................................................................................................. 1 1.2 Poly l-Lactic Acid (PLLA) and Poly Methyl Methacrylate (PMMA) ................... 2 1.2.1 Structure, Synthesis and Properties of PLLA ...............................................3 1.2.2 Structure, Synthesis and Properties of PMMA ............................................5 1.2.3 Approved Applications of PLLA and PMMA by U. S. Food and Drug Administration (FDA)......................................................................................7 1.3 Polymer Properties Modification............................................................................... 7 1.3.1 Polymer Physical Properties............................................................................8 1.3.2 Compounding Versus Blending .......................................................................9 1.4 Polymer Foams ..........................................................................................................10 1.4.1 Foaming: Theoretical Aspects.......................................................................11 1.4.2 Foaming Techniques ...................................................................................... 12 1.4.3 Cellular Morphologies................................................................................... 14 1.5 Supercritical CO 2 in Polymer Processing ................................................................15 1.5.1 Mathematical Models for Prediction of Gas Solubility, Gas Diffusion and Glass Transition............................................................................................ 16 i v Reproduced with permission of the copyright owner. Further reproduction prohibited without permission. 1.5.1.1 Gas Solubility in Polymers ...............................................................16 1.5.1.2 Gas Diffusivity in Polymers ........................................................... 23 1.5.1.3 Glass Transition for Polymer-Gas System ....................................25 1.5.2 CO2 induced crystallization in polymers ...................................................... 26 1.6 Interaction of CO 2 with PLLA................................................................................. 28 1.7 Interaction of CO 2 with PMMA............................................................................... 29 1.8 Research Obj ects ....................................................................................................... 31 References......................................................................................................................... 32 Chapter 2: Experimental.................................................................................................... 38 2.1 Introduction ................................................................................................................38 2.2 Sample Preparation................................................................................................... 38 2.2.1 Materials..........................................................................................................38 2.2.2 Melting Blending............................................................................................38 2.2.3 Compression Molding.................................................................................. 39 2.3 Blend Characterization.............................................................................................. 39 2.3.1 Differential Scanning Calorimetry (DSC) ....................................................39 2.3.2 Thermo gravimetric Analysis (TGA) ...........................................................41 2.3.3 X-ray Diffraction (XRD) ...............................................................................42 2.4 CO2 Sorption Kinetic Studies.................................................................................