Expanding molecular understanding of large deformation in Thermoplastic Polyurethanes

Shuze Zhu, Nikolaos Lempesis, Pieter J. in ‘t Veld, and Gregory C. Rutledge

Macromolecules, in press, 2018, https://pubs.acs.org/doi/10.1021/acs.macromol.8b01922

Thermoplastic polyurethanes (TPUs) are candidates for a number of applications where outstanding resilience and ability to dissipate energy under large compressive deformation are needed. TPUs possess complex, heterogeneous structure where chemically distinct segments segregate into hard and soft domains, which pose significant challenges for the molecular level mechanistic understanding of their mechanical properties and associated multiscale modeling and experimentation. 

From our prevous work of large tensile deformation (https://pubs.acs.org/doi/abs/10.1021/acs.macromol.7b02367), we found several distinct mechanisms for Mullins effect, superior resilience, and dissipation of energy at large tensile strains in TPUs. Nevertheless, the subsequent investigation of the deformation mechanism of TPUs under large compressive strains suggests a few distinct mechanisms in addition to those observed under large tensile deformation. These distinct mechanisms include fragmentation and restacking, etc. In the current work of large compressive deformation (https://pubs.acs.org/doi/10.1021/acs.macromol.8b01922), we report our observations with particular focus on those distinct mechanisms. We also discuss the source of resilience in TPUs during cyclic loading, which was not discussed in our previous study of large tensile deformation.

Together with our previous study of deformation mechanisms under large tensile strain, the current work expands our understanding of large strain deformation mechanisms for TPUs on the molecular level.