Co-Injecting Bioplastics: Investigating Process Engineering and Performance by Nicholas Hotz A Thesis Presented to The University of Guelph In partial fulfillment of requirements for the degree of Master of Applied Science in Engineering Guelph, Ontario, Canada © Nicholas Hotz, April, 2015 Abstract Co-Injecting Bioplastics: Investigating Process Engineering and Performance Nicholas Hotz Advisors: Dr. Amar K. Mohanty University of Guelph, 2015 Dr. Manjusri Misra Mechanical performance improvement of brittle bioplastic polylactic acid (PLA) was investigated through the use of a novel processing method: co-injection moulding. Co-injection moulding produces layered products with distinct core and skin phases. PLA toughening was attempted via encapsulation in a polycaprolactone (PCL) skin. Select co-injection operating parameters were assessed regarding their ability to influence product morphology. Injection speeds and skin melt temperature were observed to have negative effects on core content and advancement, while core ratio had a positive influence. These results were used to develop samples with up to 60% biobased PLA content. Comparable PLA/PCL blend samples were produced for mechanical testing. Co- injection products had better tensile strength and stiffness compared to similar blends, but the layered structure was less adept at resisting flexural stress. Impact resistance improved with co- injection compared to neat PLA. Co-injection was identified as a functional bioplastics processing method which results in unique mechanical behaviour. Acknowledgements Many thanks to my advisors, Dr. Amar Mohanty and Dr. Manjusri Misra, for giving me the opportunity to advance my academic career in an interesting and challenging scientific field. Their confidence in my abilities has been very supportive and I am appreciative of all the valuable experiences I have gained that have helped me to develop as a researcher and as a person. Thanks also to my committee advisor, Dr. Lubitz, for his time, interest, and encouragement, and to my examination chair, Dr. Runciman, for his drive to make my thesis the best it could be. Thank you to my colleagues at the Bioproduct Discovery and Development Centre (BDDC) for your camaraderie, your insight, your advice, your guidance, and the many, many hours generously offered by a select few to help facilitate my work. My deepest regards and best wishes in your studies and future careers. This research was funded by the Natural Sciences and Engineering Research Council (NSERC), (Canada) through the Discovery Grants Program (PI: Mohanty) and the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA). Equipment support was provided by the Canada Foundation for Innovation (CFI) - Leaders Opportunity Fund (LOF). The financial support of these organizations is gratefully acknowledged. Lastly, and above all else, my unending thanks to my family; to my son, Dexter, for his delightful charms in the toughest times, and most of all to my wife, Christina, whose unending love and support I never would have been able to succeed without. iii Table of Contents Abstract ............................................................................................................................................................... ii Acknowledgements ........................................................................................................................................... iii Table of Contents ............................................................................................................................................. iv List of Tables .................................................................................................................................................... vii List of Figures .................................................................................................................................................... ix Abbreviations and Symbols ............................................................................................................................ xv Chapter 1 : Introduction ................................................................................................................................. 1 Chapter 2 : Literature Review ........................................................................................................................ 4 2.1 Bioplastics Overview ........................................................................................................................ 4 2.1.1 Conventional Plastics ............................................................................................................... 4 2.1.2 Biobased Plastics ....................................................................................................................... 5 2.1.3 Biodegradable Plastics .............................................................................................................. 6 2.1.4 Biobased and Biodegradable Plastics ..................................................................................... 9 2.2 Recent Developments in Bioplastics ............................................................................................ 10 2.2.1 Durable Bioplastics ................................................................................................................. 11 2.2.2 Biodegradable Bioplastics ...................................................................................................... 13 2.3 Polylactic Acid ................................................................................................................................. 16 2.3.1 Background .............................................................................................................................. 16 2.3.2 Toughening Strategies ............................................................................................................ 17 2.4 Polycaprolactone (PCL) ................................................................................................................. 29 2.5 PLA/PCL Blends ............................................................................................................................ 30 2.5.1 Modifying PLA/PCL Blends ................................................................................................ 31 2.6 Processing ......................................................................................................................................... 35 2.7 Extrusion .......................................................................................................................................... 35 2.7.1 Temperature............................................................................................................................. 37 2.7.2 Throughput .............................................................................................................................. 39 2.7.3 Screw Speed ............................................................................................................................. 39 2.7.4 Moisture Content .................................................................................................................... 40 2.7.5 Screw Design ........................................................................................................................... 40 2.7.6 Die Swell .................................................................................................................................. 41 iv 2.8 Injection Moulding .......................................................................................................................... 44 2.9 Co-Injection Moulding ................................................................................................................... 45 2.9.1 Influence of Operating Parameters ...................................................................................... 48 2.9.2 Viscosity Ratio ......................................................................................................................... 48 2.9.3 Melt Temperature ................................................................................................................... 49 2.9.4 Mould Temperature ................................................................................................................ 50 2.9.5 Injection Speed ........................................................................................................................ 51 2.9.6 Injection Volume .................................................................................................................... 52 2.9.7 Fillers......................................................................................................................................... 52 Chapter 3 : Research Problem ..................................................................................................................... 53 3.1 Objectives ......................................................................................................................................... 56 3.2 Hypothesis ........................................................................................................................................ 56 Chapter 4 : Experimental Section ............................................................................................................... 59 4.1 Materials ...........................................................................................................................................