Segmented elastomers such as polyurethane-urea (PUU) have attracted considerable research interest in the last decade due to their excellent high strain rate properties. Given the sheer number and structural diversity of potential molecules that can constitute the hard and soft segments in PUUs, a facile way to correlate molecular structure to high strain rate response can help accelerate development of PUUs optimised for specific dynamic loading requirement. In this contribution, we will report on our preliminary efforts at experimentally elucidating how molecular constituents of the PUUs correlates to their properties at multiple (length and time) scales.
Briefly, we have synthesized a series of model PUUs, with a wide range of quasi-static strength and dynamic damping properties, by careful tuning of both hard and soft segments. Through detailed characterisation, we were able to correlate PUU chemical structures to strength and damping properties – revealing molecular design rules for optimising both strength and damping in these PUUs. We then attempted to deconvolute the contribution of strength and damping properties on high strain rate properties by subjecting thin films of PUU to microscale, laser-induced projectile impact tests. Correlations between changes in damping and strength of PUU to the changes in the projectile rebound and perforation velocities regime were observed – hinting at the possibility of extending these molecular design rules to optimising high velocity and high strain rate energy dissipation properties of PUU.
