Abstract:ln view of packaging sustainability commitments towards a more circular economy, there is a need to develop packaging materials that are readily recyclable with properties that guarantee quality and safety of food products throughout their shelf life.

Barrier paper has emerged as an alternative to conventionally used multilayer plastic laminates, thanks to the widely available infrastructure for paper recycling. Recently developed barrier papers match the overall performance of existing difficult-to-recycle multilayer plastic laminates. Integration of thin inorganic metal layer to the structure is the state-of-the-art for barrier, without compromising recyclability.

During its life cycle, a packaging material is exposed to different environmental and mechanical stresses which might alter the integrity of such thin metal layers which is known to be brittle. Such stresses not only occur during the forming of a package, its distribution, transport and use but also, due to the hygroscopic nature of fiber-based materials, during its exposure to harsh climatic conditions, e.g. in tropical climates where paper undergoes hygro-expansion.

This study aimed at understanding the underlying mechanisms and stress levels leading to unacceptable barrier losses, allowing an early identification of the limits of a given material and the development of new structures displaying a better mechanical and climate resilience.

The effect on barrier properties of tensile strains induced by high humidity conditions and mechanical stresses have been evaluated. Results show that elastic deformations have limited effects on the barrier properties of the high barrier paper investigated in this work whereas permanent strains result in barrier loss. The extent of barrier loss is highly dependent on the material structure. Most recent barrier paper developments yield materials that are very resilient and retain high performance over their life cycle, guaranteeing safety and quality of food.

This publication finally provides a methodology to characterize barrier resilience of paper-based materials which could provide critical insights for novel material development.