A sustainable vitrimer from depolymerized lignin: Synthesis and reworkable application.

Area of Science:

• Materials Science
• Polymer Chemistry
• Sustainable Chemistry

Background:

• Lignosulfonate, a lignin derivative, is an abundant, renewable resource.
• Developing sustainable thermosets with enhanced properties like flame retardancy and recyclability is crucial.
• Vitrimers offer a unique combination of thermoset durability and thermoplastic processability.

Purpose of the Study:

• To synthesize a sustainable vitrimer from epoxidized and depolymerized lignosulfonate (EpddLS).
• To investigate the structure-property relationships, including dynamic covalent behavior and flame retardancy.
• To demonstrate the potential for reprocessing, reworkability, and self-healing in bio-based thermosets.

Main Methods:

• Lignosulfonate was demethylated, depolymerized, and functionalized with epoxide groups.
• EpddLS was blended with DGEBA and cured with MNA using zinc stearate catalyst.
• Characterization included stress relaxation, differential scanning calorimetry, mechanical testing, and flame retardancy assessment (UL-94).

Main Results:

• The synthesized vitrimer exhibited rapid stress relaxation (τ ≈ 2 s at 160 °C) and good thermal stability (Tg ≈ 100 °C).
• The material demonstrated excellent mechanical integrity and intrinsic flame retardancy (UL-94 V-0) without additives.
• Successful reprocessing, reworkability, and self-healing capabilities were confirmed due to dynamic transesterification bonds.

Conclusions:

• A sustainable, high-performance vitrimer was successfully synthesized from lignosulfonate.
• The bio-based thermoset possesses inherent flame retardancy and recyclability, aligning with circular economy principles.
• This work highlights the potential of lignin valorization for creating advanced, eco-friendly materials.