Studies on the Blending of Poly(Lactic Acid) and Acrylonitrile Butadiene Styrene by Ryan Vadori A Thesis presented to The University of Guelph In partial fulfilment of requirements for the degree of Master of Applied Science in Biological Engineering Guelph, Ontario, Canada © Ryan Vadori, Dec, 2012 ABSTRACT STUDIES ON THE REACTIVE BLENDING OF POLY(LACTIC ACID) AND ACRYLONITRILE BUTADIENE STYRENE RUBBER Ryan Vadori Advisor: Dr. Manjusri Misra University of Guelph, 2012 Co- Advisor: Dr. Amar K. Mohanty The polymer materials industry is heavily dependent on the use of petroleum based plastics. This poses a problem, as the world is facing ongoing petroleum supply problems. A need exists for a bio-carbon based polymer material that has the performance and cost of currently used petroleum plastics. However, the overall performance of current bio-based plastics indicate that they must be somehow supplemented to achieve the properties of that of petroleum-based polymers. The low impact strength and thermal stability of poly(lactic acid), PLA are targets for improvement. One option is for development is through blending with acrylonitrile butadiene styrene (ABS). The viability and efficacy of using these two polymers as blending partners is investigated. The PLA used in these studies has unique and interesting crystallization properties. These have been examined and detailed in part 1. The second part of study includes neat polymer properties, miscibility analysis, and large scale process results. This results in an optimized blending ratio on which to go forward with development. The mechanical, thermal, and morphological properties are investigated in these studies. Significance of this research and development is widespread, as the material developed has the potential to reduce the use of petroleum-based carbon in plastics. iii Acknowledgements Grateful does not begin to describe my feelings for my advisors, Dr. Amar Mohanty and Dr. Manju Misra, who have welcomed me into their laboratory. They have taught and guided my through my attaining this degree in ways that go beyond their expected duties. I am indebted to them for guiding me to reach toward my potential as a young and aspiring scientist. I am also grateful to my committee advisor, Dr. Fantahun Defersha who has brought perspective to me work. I am thankful to my colleagues who I have had the privilege to share our workspace. There was a time when I did not think that I would finish my undergraduate degree in engineering. It is because of the support and encouragement of my family, especially my Mother and Father that I was able to complete. This master’s degree too is due to them. The final but certainly not the least of my acknowledgments is to my fiancé. Her patience and understanding while I complete my studies are truly the attributes more commonly seen from members of sainthood. Her unending support is the reason for that I am attaining this degree. The financial support from the 2010 Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA)/University of Guelph -Bioeconomy for Industrial Uses Research Program, Natural Sciences and Engineering Research Council (NSERC) AUTO21 NCE project and Grain Farmers of Ontario (GFO), to carry out this research is gratefully acknowledged. iv Table of Contents Selected Abbreviations ............................................................................................ x List of Tables ......................................................................................................... vii List of Figures ....................................................................................................... viii 1. Introduction .................................................................................................... 1 2. Literature Review .......................................................................................... 3 2.1 Bioplastics ........................................................................................................ 3 2.2 Poly(lactic acid) ................................................................................................ 5 2.3 Review of Traditional Plastics with Special Focus on ABS ............................ 6 2.4 Polymer Processing .......................................................................................... 9 2.5 Crystallization and Polymer Properties ..........................................................13 2.6 Polymer Blending Theory ..............................................................................14 2.8 Toughening and Compatibilization ................................................................17 2.9 Bio-based and Biodegradable Plastic Blends .................................................20 3. Problem Statement ......................................................................................22 4. Objectives and Hypotheses .........................................................................22 4.1 Objective 1 ......................................................................................................23 4.2 Objective 2 ......................................................................................................23 4.3 Objective 3 ......................................................................................................24 v 4.4 Objective 4 ......................................................................................................24 5. Experimental Part .......................................................................................25 5.1 Materials .........................................................................................................25 5.2 Experimental Design ......................................................................................26 5.3 Compounding of PLA and ABS .....................................................................27 5.3.1 Drying ............................................................................................................. 27 5.3.3 Processing for Study 1 .................................................................................. 27 5.3.2 Processing for Study 2 .................................................................................. 27 5.4 Characterization ..............................................................................................28 5.4.1 Mechanical properties .................................................................................. 28 5.4.2 Differential Scanning Calorimetry (DSC) .................................................. 28 5.4.3 Dynamic Mechanical Analysis (DMA) ........................................................ 29 5.4.4 Optical Microscopy ....................................................................................... 29 6. Results and Discussion Study 1: Process Engineering .............................30 6.1 DSC and Crystallization .................................................................................30 6.2 Mechanical Properties as a Function of Mold Temperature ..........................36 6.3 Mechanical Properties as a Function of Time ................................................41 6.4 Dynamic Mechanical Analysis .......................................................................43 6.5 Optical Microscopy ........................................................................................46 6.6 Study 1 Conclusions .......................................................................................49 vi 7. Results and Discussion Part 2: Polymer Blending ...................................51 7.1 Viability of Blending PLA/ABS-1 .................................................................51 7.3 Blend Optimization and Miscibility Analysis ................................................55 7.4 Pilot Scale Extrusion and Injection Molding .................................................61 7.5 Study 2 Conclusion .........................................................................................70 8. Economic Assessment and Significance .....................................................70 9. Conclusion ....................................................................................................72 10. Future Recommendations ...........................................................................73 11. References .....................................................................................................74 vii List of Tables Table 2.1: Glass transition and melting temperatures of PLA 13 Table 6.1: Crystallinity of each molded sample as a function of time 34 Table 6.2: Mechanical properties of PLA molded at 30°C, 60°C, 90°C 38 Table 7.1: Mechanical properties of neat PLA, ABS 1, ABS 2, and a sample from industry 55 Table 7.2: Mechanical properties of polymer blends according to the rule of mixtures 56 Table 7.3: Thermal properties of neat PLA, ABS-1 and ABS-2 57 Table 7.4: Mechanical properties of PLA:ABS-1 with decreasing PLA content 60 Table 7.5: Mechanical properties of neat PLA, ABS-1 and PLA:ABS-1 blend after processing in large scale machinery 65 viii List of Figures Figure 2.1: Bioplastic categorization 5 Figure 2.2: Schematic of the polymerization of PLA 6 Figure 2.3: Schematic of the screw cross section of a twin screw extruder 11 Figure 6.1: DSC curves of samples molded at 30°C, 60°C, 90°C at two days after molding 32 Figure 6.2: DSC curves of samples molded at 30°C, 60°C, 90°C at five days after molding 33 Figure 6.3: DSC curves of samples molded at 30°C, 60°C, 90°C