Dr. Donya Ramimoghadam

Abstract:

“Recyclable-by-design” is an eco-design strategy aimed at promoting closed-loop material recovery at the end of a product’s life cycle ¹. This approach represents a state-of-the-art technological solution to the challenges of sustainable polymer recycling and addresses the socio-economic impact of plastic pollution. In this study, we adopted a recyclable-by-design strategy to re-engineer polyurethane polymers and facilitate their end-of-life recyclability.

The covalent adaptable networks (CANs) are polymers with dynamic covalent bonds (DCBs), extensively used as structural materials in composite, coating, adhesive, and sealant applications ². DCBs in these networks offer intrinsic reversibility while maintaining the robustness of covalent bonds, allowing the formation of mechanically stable polymers that respond to external stimuli ³.

In this study, we first synthesized a novel diol monomer incorporating an acylhydrazone linkage, which was then used to produce a thermoset polyurethane in combination with a trimer isocyanate. The resulting polymer demonstrated the ability to depolymerize under mildly acidic conditions at room temperature, indicating reversible behavior. The polyurethane films exhibited a range of desirable properties, including strong mechanical integrity (maximum tensile strength of 28.07 MPa), excellent solvent resistance, and thermal stability—qualities that make them well-suited for high-performance applications. Notably, the dynamic polyurethane showed controlled degradation in the presence of acetone and acetic acid, with recyclability demonstrated across three cycles. The recycled self-standing films retained mechanical performance comparable to a non-dynamic control polymer, although a gradual decline in tensile strength was observed over repeated cycles.

In addition, the polyurethane films exhibited self-healing properties, repairing surface cuts under mild conditions. Coating adhesion and pencil hardness tests also yielded promising results, highlighting the potential of this material for use in protective and functional coatings.