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Effect of Loading and Process Conditions on the Mechanical University of Massachusetts Amherst ScholarWorks@UMass Amherst Open Access Dissertations 2-2009 Effect of Loading and Process Conditions on the Mechanical Behavior in SEBS Thermoplastic Elastomers (TPEs) Mohit Mamodia University of Massachusetts Amherst, [email protected] Follow this and additional works at: https://scholarworks.umass.edu/open_access_dissertations Part of the Polymer and Organic Materials Commons Recommended Citation Mamodia, Mohit, "Effect of Loading and Process Conditions on the Mechanical Behavior in SEBS Thermoplastic Elastomers (TPEs)" (2009). Open Access Dissertations. 32. https://doi.org/10.7275/nxrs-2151 https://scholarworks.umass.edu/open_access_dissertations/32 This Open Access Dissertation is brought to you for free and open access by ScholarWorks@UMass Amherst. It has been accepted for inclusion in Open Access Dissertations by an authorized administrator of ScholarWorks@UMass Amherst. For more information, please contact [email protected]. EFFECT OF LOADING AND PROCESS CONDITIONS ON THE MECHANICAL BEHAVIOR IN SEBS THERMOPLASTIC ELASTOMERS (TPEs) A Dissertation Presented by MOHIT MAMODIA Submitted to the Graduate School of the University of Massachusetts Amherst in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY February 2009 Polymer Science and Engineering © Copyright by Mohit Mamodia 2009 All Rights Reserved EFFECT OF LOADING AND PROCESS CONDITIONS ON THE MECHANICAL BEHAVIOR IN SEBS THERMOPLASTIC ELASTOMERS (TPEs) A Dissertation Presented by MOHIT MAMODIA Approved as to style and content by: ____________________________________ Alan J. Lesser, Chair ____________________________________ Samuel P. Gido, Member ____________________________________ Henning H. Winter, Member __________________________________________ Shaw L. Hsu, Department Head DEDICATION Aditi, Mummy & Papa ACKNOWLEDGMENTS I would like to thank Prof. Alan Lesser for being a great adviser. He was instrumental not only as an advisor but as a true mentor and infact a guru. It was because of his guidance that helped me in growing as a research scientist. He taught me the importance of being responsible for my own research work in the lab. I enjoyed immensely the freedom he gave me in trying out various things in the lab. This greatly enhanced my knowledge of application of the basic principles of science for solving material science problems. I am also extremely grateful to him for all the opportunities he provided me in presenting my work at various places. He taught me very patiently the importance of communicating ideas simply and effectively. My sincere thanks to Prof. Henning H. Winter and Prof. Samuel P. Gido for serving on my committee. They provided me numerous suggestions during my work that greatly improved the quality of this thesis. I consider it a great privilege for me to have such accomplished scientists on my committee. I am extremely grateful to Prof. Wim De Jeu for his help, insight and guidance with x-ray scattering work. I truly cherish the great discussions I had with him. I would like to thank past members of the Lesser group Kishore, Peter, Dr. Xianbo Hu, Kevin, Melissa and Jian for all their help in the lab. Kishore helped me a lot in my first year when I was totally new to research. He also taught me deformation calorimetry which is unique device by itself. Discussions with Peter were really helpful. He also taught me the art of building devices. His expertise was really helpful in building the high strain-rate tensile testing device. His suggestions and help are greatly appreciated. The present Lesser group Donna, Joonsung, Scott, Andrew, Jared, Sinan, v Kate, Naveen, Dave and Michael are a cool bunch and we all had so much fun together both inside and outside the lab. My acknowledgements to MRSEC, CUMIRP and KRATON Polymers for all the funding support through the years. Many thanks to Evgenia, Sekar, Lou Raboin and John Domian for all the help through the years. The graduate life became simpler with the support of the PS&E office group-Vivien, Greg, Sophie, Ann, Katera and others. There are numerous friends Malvika, Vikram, Priyanka and Ruchir who have made my stay at UMass very pleasant. I would especially like to thank Malvika who was a very good friend. She really helped me in preparing for my first conference and her suggestions really helped me in improving my presentation skills. I would also like to thank few people who not only were great friends, but they created a family away from home. I call them my US-family. First of all Naveen, with whom I have shared room for almost entire of my stay in Amherst. Only my wife Aditi could replace him. He is like a brother to me and was always there in my good and bad times. Divya (gudiya) she was closest to me in first year, but then went to University of Wisconsin Madison. Rachit and Ila were almost like local guardians to me. I would always cherish the moments when we used to spend in their house almost every weekend. Rishi and madhura were also great friends. Rishi was always there to help and I would miss his sense of humor. I would also like to thank Gaurav and Somya for being such nice friends. I would also like to thank my parents in law for their love, trust and support. Their blessings were always there with me. I would like to thank Abhinav, Arti bhabhi and Shonna for their wishes. vi I would like to thank my sisters Sakshi and Richa for their material and emotional support. They always wanted the best out of me and were always proud of their brother. I know how happy they are always for all of my accomplishments. I also thank my brother in law Ritesh (jiju) and my nephew Kush for all their constant love and support. For their constant love and support, I would like to thank my dad and mother. I guess the word ‘thank’ appears too small for them. Whatever I am today is all because of them. I always wonder about my dad’s farsightedness. I still remember how my mother used to sit with me and my sisters during our school times and teach all the subjects. Finally for her endless love I would like to thank my wife Aditi. Although she has been in my life for past one and a half years, but she was my strength all this time. She has done and sacrificed so much for me. She makes my life complete. Whatever I have achieved so far, and would like to in future, will be for her. I absolutely cannot imagine this without you. vii ABSTRACT EFFECT OF LOADING AND PROCESS CONDITIONS ON THE MECHANICAL BEHAVIOR IN SEBS THERMOPLASTIC ELASTOMERS (TPEs) FEBRUARY 2009 MOHIT MAMODIA, B.TECH., INDIAN INTSTITUTE OF TECHNOLOGY BOMBAY M.S., UNIVERSITY OF MASSACHUSETTS AMHERST Ph.D., UNIVERSITY OF MASSACHUSETTS AMHERST Directed by: Professor ALAN J. LESSER Styrenic block copolymer thermoplastic elastomers are one of the most widely used thermoplastic elastomers (TPEs) today. The focus of this research is to fundamentally understand the structure-processs-property relationships in these materials. Deformation behavior of the block copolymers with cylindrical and lamellar morphologies has been investigated in detail using unique techniques like deformation calorimetry, transmission electron microscopy (TEM), combined in-situ small angle x- ray and wide angle x-ray scattering (SAXS/WAXS). The research involves the study of structural changes that occur at different length scales along with the energetics involved upon deformation. The structural changes in the morphology of these systems on deformation have been investigated using combined SAXS/WAXS setup. Small angle x-ray scattering probed the changes at the nano-scale of polystyrene (PS) cylinders, while wide angle x-ray scattering probed the changes at molecular length viii scales of the amorphous/crystalline domains of the elastomeric mid-block in these systems. TEM analysis of the crosslinked elastomers (by UV curing) further confirms the interpretation of structural details as obtained from SAXS upon deformation. New structural features at both these length scales have been observed and incorporated into the overall deformation mechanisms of the material. Characteristic structural parameters have been correlated to differences in their mechanical response in the commercially relevant cylindrical block copolymers. Effect of various process conditions and thermal treatments has been investigated. The process conditions affect the structure at both micro-scopic (grain size) and nano-scopic (domain size) length scales. A correlation has been obtained between a mechanical property (elastic modulus) and an easily measurable structural parameter (d-spacing). Effect of various phase transitions such as order-to-order transition has been studied. Selective solvents can preferentially swell one phase of the block copolymer relative to other and thus bring a change in morphology. Such kinetically trapped structures when annealed at higher temperature try to achieve their thermodynamic equilibrium state. Such changes in morphology significantly affect their tensile and hysteretic response. In another work it has been shown that by carefully compounding these styrenic block copolymers having different morphologies, it is possible to completely disrupt the local scale order and remove the grain boundaries present in these materials. Finally, a new test technique has been developed, by modifying an existing Charpy device to test polymeric films at a high strain rate. A custom designed load-cell is used for force measurements which imposes harmonic oscillations on a monotonic ix loading signal.
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