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Shi-Qing Wang "A unified framework to understand ductility in glassy polymers :..."

A unified framework to understand ductility in glassy polymers : from crazing, brittle-to-ductile transition to rubber-toughened polymers

Shi-Qing Wang, Faculty of Department of Polymer Science, University of Akron, Akron, OH

le vendredi 11 octobre à 14h à l’amphi Boreau

Abstract
In my lab, we focus on building a molecular-level understanding of polymer mechanics in both liquid and solid states. This is a journey that involves three episodes or steps : a. Phenomenology and conceptual foundation of polymer melt rheology, b. Molecular mechanics of polymer glasses, c. Brittleness and ductility of semicrystalline polymers. The latter two subjects can only be understood after the molecular foundation [1] for polymer melt rheology has been established. In this talk, I will concentrate on subject b, exploring how we can understand the remarkable ductility of glassy polymers. In a pedagogical way, I will explain why a valid theory to explain yielding of glassy polymers must address when the polymers fail to remain ductile, i.e., unable to yield and undergo brittle fracture. The universally applied Eyring idea of activation alone is powerless to provide the foundation for the molecular mechanics of glassy polymers. Rich experiences with melt rheology have provided us the crucial ingredients to formulate the basis [2] for all aspects of mechanical behavior of polymeric glasses including brittle-ductile transition, crazing and rubber-toughening.

References
[1] Nonlinear polymer rheology : macroscopic phenomenology and molecular foundation, S. Q. Wang, Wiley (2018)
[2] A phenomenological molecular model for brittle-ductile transition and yielding of polymer glasses, S. Q. Wang et al., J. Chem. Phys. 141, 094905 (2014).


Biography
Shi-Qing Wang was educated in China and arrived in the US in fall 1982 through the Chinese-US Physics Examination and Application (CUSPEA) program after earning a BS in Physics in Wuhan University. He spent the first nine months at University of Rochester before transferring to University of Chicago where received his Ph.D. degree in Physics in 1987, working with Karl Freed on renormalization group calculations of linear viscoelastic properties of polymer solutions. After two years of postdoctoral research at University of California at Los Angeles with William Gelbart, Shi-Qing Wang joined in fall 1989 the faculty of Macromolecular Science and Engineering at Case Western Reserve University, and rose to Full Professor in 1998. Since fall 2000, he has been on the faculty of Department of Polymer Science at University of Akron. His research interest is polymer physics and engineering. First half of his career efforts has resulted in a comprehensive monograph on polymer rheology : Nonlinear Polymer Rheology – Macroscopic phenomenology and Molecular foundation (Wiley, 2017). He is a fellow of both APS and AAAS...www.researchgate.net/profile/Shi-Qing_Wang

08/10/19

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