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  • AME Seminar

    Wed, Mar 01, 2023 @ 03:30 PM - 04:30 PM

    Aerospace and Mechanical Engineering

    Conferences, Lectures, & Seminars

    Speaker: Junsoo Kim, Harvard University

    Talk Title: Fracture of Highly Entangled Polymer Networks

    Abstract: Polymers pollute our planet. Part of this pollution comes from tires. Every year, 0.8 kg of rubber particles are shed by tires per capita in the world.1 A recent study showed that rainstorms wash the rubber particles into rivers, where toxic chemical compounds leach out and kill fish.2 Despite its significant impact on the environment, the development of rubbers resistant to fracture has been stagnant for decades. In this talk, I will discuss how to improve the fracture properties of polymer networks, such as rubbers and gels. The key idea is that entanglements stiffen polymers but do not embrittle them, whereas crosslinks stiffen polymers and embrittle them (i.e., stiffness-toughness conflict). Therefore, highly entangled polymer networks in which entanglements greatly outnumber crosslinks can be both stiff and tough. Furthermore, whereas traditional toughening mechanisms are based on sacrificial bonds causing hysteresis and fatigue, highly entangled polymer networks achieve high toughness by stress deconcentration, leading to high strength, elasticity, and fatigue resistance. This toughening mechanism is based on the polymer topology, not chemistry, so it is generally applicable to many other polymer systems, such as various monomers, preexisting polymers,4 and filled rubbers.5 It is hoped that this work will reactivate the development of wear-resistant tires. Such materials can also be explored in other high-volume applications such as dampers and belts, as well as emerging applications such as soft robots, wearable devices, tissue replacements, bioprinting, and humanoids.

    1 P. J. Kole, A. J. Löhr, F. G. A. J. V. Belleghem, A. M. J. Ragas, Int. J. Environ. Res. Public Health, 14(10), 1265 (2017)
    2 Z. Tian et. al., Science, 371(6525), 185-189 (2020)
    3 J. Kim*, G. Zhang*, M. Shi, Z. Suo, Science, 374(6564), 212-216 (2021)
    4 G. Nian*, J. Kim*, X. Bao, Z. Suo, Adv. Mat., 34(50), 2206577 (2022)
    5 J. Steck*, J. Kim*, Y. Kutsovsky, Z. Suo, under review

    Biography: Junsoo Kim is a postdoctoral researcher at the John A. Paulson School of Engineering and Applied Sciences, Harvard University. He earned his Ph.D. in the Material Science and Mechanical Engineering department at Harvard University in 2022, where he studied fracture of soft materials. Before joining Harvard in 2017, he was a researcher at Electronics Telecommunications Research Institute since 2014. He earned his M.S. in 2013 and B.S. in 2011 at Seoul National University in South Korea. He co-authored 31 papers in peer-reviewed journals, registered six patents, and received fellowships, including the Ilun Science and Technology Foundation (2013) and Kwanjeong Educational Foundation (2017).

    Host: AME Department

    More Info: https://ame.usc.edu/seminars/

    Webcast: https://usc.zoom.us/j/98775609685?pwd=a2lSd01oY0o2KzA4VWphbGxjWk5Qdz09

    Location: John Stauffer Science Lecture Hall (SLH) - 102

    WebCast Link: https://usc.zoom.us/j/98775609685?pwd=a2lSd01oY0o2KzA4VWphbGxjWk5Qdz09

    Audiences: Everyone Is Invited

    Contact: Tessa Yao

    Event Link: https://ame.usc.edu/seminars/

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