3D Fluorescent Mapping of Invisible Molecular Damage after Cavi-tation in Hydrogen Exposed Elastomers

TL;DR

This study introduces a novel 3D fluorescent mapping technique to visualize internal molecular damage in elastomers caused by cavitation, revealing complex crack morphologies and fracture behaviors after rapid decompression.

Contribution

It presents a new non-destructive method for 3D visualization of molecular damage in polymers, enhancing understanding of fracture mechanisms under cavitation.

Findings

Cavities during decompression correlate with damaged regions revealing fracture loci.

Damage regions exhibit flower-like crack morphologies with arrest lines.

Cavity growth involves discontinuous fracture of multiple crack planes.

Abstract

Elastomers saturated with gas at high pressure suffer from cavity nucleation, inflation, and deflation upon rapid or explosive de-compression. Although this process often results in undetectable changes in appearance, it causes internal damage, hampers func-tionality (e.g., permeability), and shortens lifetime. Here, we tag a model poly(ethyl acrylate) elastomer with {\pi}-extended anthracene-maleimide adducts that fluoresce upon polymer chain scission, and map in 3D the internal damage present after a cycle of gas satu-ration and rapid decompression. Interestingly, we observe that each cavity observable during the decompression results in a dam-aged region, the shape of which reveals a fracture locus of randomly oriented penny-shape cracks (i.e., with a flower-like morpholo-gy) that contain crack arrest lines. Thus, cavity growth likely proceeds discontinuously (i.e., non-steadily) through the stable and unstable fracture of numerous 2D crack planes. This non-destructive methodology to visualize in 3D molecular damage in polymer networks is novel and serves to understand how fracture occurs under complex 3D loads, predict mechanical aging of pristine look-ing elastomers, and holds potential to optimize cavitation-resistant materials.