06/18/19: Wanting’s ACS Macro Letter paper is published. Congrats!

Entanglement Density-Dependent Energy Absorption of Polycarbonate Films via Supersonic Fracture

Edwin P. Chan,†,‡ Wanting Xie,‡,§,? Sara V. Orski,† Jae-Hwang Lee,? and Christopher L. Soles†
† Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States
§ Department of Physics and ? Department of Mechanical and Industrial Engineering, University of Massachusetts, Amherst, Massachusetts 01003, United States

‡These authors contributed equally to this work.

Abstract
The fracture behavior of glassy polymers is strongly coupled to molecular parameters such as entanglement density as well as extrinsic parameters such as strain rate and test temperature. Here we use laser-induced projectile impact testing (LIPIT) to study the extreme strain rate (?10^7 /s) puncture behavior of free-standing polycarbonate (PC) thin films. We demonstrate that changes to the PC molecular mass and the degree of plasticization can lead to substantial changes in the specific puncture energy. We relate these changes to the alteration of the entanglement density of the polymer that determines the underlying failure mechanism as well as the size of the deformation zone.  LINK to the paper