Saponification as a chemical tool for the recycling of biobased thermosetting resins: closing the loop toward circular materials

Thermosetting polymers are essential for high-performance applications due to their excellent thermal and mechanical properties, yet their crosslinked structure prevents efficient mechanical recycling, creating major end-of-life challenges. At the same time, the development of biobased alternatives to conventional petroleum-based thermosets is intensifying, raising critical questions regarding their recyclability and sustainability. In this context, the development of robust chemical recycling strategies becomes a key step toward circular thermoset materials.

This study investigates the chemical recycling of various epoxy-acid biobased thermosetting resins through a saponification-driven depolymerization approach. A flexible model network based on epoxidized vegetable oil and bio-derived diacids was first examined. The solvolysis was monitored through an in situ calorimetric methodology, enabling tracking of conversion as a function of time. This strategy provided a comprehensive characterization of the recycling process based on kinetic analysis. The methodology was then extended to high glass transition temperature thermosets based on fully biobased phloroglucinol-derived networks, highlighting the replicability of the process across different formulations. Beyond depolymerization, the systematic revalorization of the recovered products was investigated. The resulting polyacid-rich fractions were charcterized by LC-MS, reused as reactive intermediates for the synthesis of new thermosetting networks, and analyzed through thermal and mechanical properties.

Altogether, this work demonstrates that saponification is an effective recycling pathway, coupling kinetic understanding with the efficient reuse of recovered fractions to form new thermosetting materials. By bridging process understanding with material reusability, this study contributes to the development of circular recycling strategies for thermosets.