Robust mechanical performance of chromium-coated polyethylene terephthalate over a broad range of conditions

Abstract

Mechanical properties of metal films on polymer substrates are normally studied in terms of the fracture and adhesion of the film, while the properties of the polymer substrate and testing conditions are overlooked. Substrate orientation and thickness, as well as strain rate and temperature effects, are examined using Cr films deposited onto polyethylene terephthalate substrates. A faster strain rate affects only the initial fracture strain of the Cr film and not the crack and buckle spacings in the high strain condition. The substrate orientation slightly changes the average crack spacing while the substrate thickness has little effect on the cracking and buckling behaviour. Straining experiments at high temperature increased the average crack spacing and led to a change in buckling mode. The lack of sizeable changes in the mechanical behaviour over the large range of testing procedures leads to a resilient material system for flexible applications.

Keywords:

• thin films
• polymers
• strain
• thermal stability
• chromium

Acknowledgements

Funding for this research has been provided by the Austrian Science Fund (FWF) under Project: P22648-N20. Experimental help was provided by C. Vieh of the University of Leoben, as well as K. Warmington, L. Bowles and D. Gopalan.