Flexible Thermoset Films from Zein: Transforming Agricultural Waste into Green Materials

In the shift towards a circular and climate-conscious materials economy, the development of thermoset plastics from renewable feedstocks is of great priority. Proteins, as abundant and naturally occurring macromolecules, are often available as industrial byproducts. They offer a sustainable and underutilised resource for polymer design (1, 2). However, materials derived from proteins typically exhibit characteristics such as brittleness, limited flexibility, and poor processability, which limits their application in advanced materials. This work explores the transformation of zein, a protein byproduct derived from maize, into crosslinked polymeric films through chemical modification and radical polymerisation as a strategy to overcome the intrinsic limitations of zein^1,2.

In the present study, zein, a lipophilic protein of no nutritional value, was acrylated to varying degrees so that the protein itself would be able to crosslink with acrylic monomers. Acrylated zein was then reacted with an acrylic monomer to form flexible, bio-based thermosetting films. The mechanical and thermal properties of the films were evaluated, and the effect of additional components, such as biobased crosslinkers, was also investigated.

The resulting materials demonstrated the preservation of zein's inherent strength and thermal stability, while exhibiting a substantial enhancement in flexibility, elongation, and toughness. It is noteworthy that lower degrees of acrylation resulted in superior performance, indicating that minimal, non-invasive chemical modifications can substantially enhance the performance of protein-based materials. The thermoset films developed in this study demonstrate considerable promise in applications such as flexible electronics, packaging, and environmentally sustainable coatings, thereby contributing to a circular and regenerative approach in materials science.

¹ Scott R. Nicholson, Nicholas A. Rorrer, Alberta C. Carpenter, Gregg T. Beckham Joule 2021, 5, 3, 673-686.

² M. Peydayesh, M. Bagnani, W. L. Soon, R. Mezzenga Chemical Reviews 2023 123 (5), 2112-2154.