Biobased Epoxy Thermoset Polymers from Depolymerized Native Hardwood Lignin

Area of Science:

• Polymer Chemistry
• Materials Science
• Sustainable Chemistry

Background:

• Developing high-performance biobased polymers is crucial for reducing reliance on fossil fuels.
• Lignin, a byproduct of the paper industry, is an abundant and renewable aromatic resource.
• Previous attempts to utilize lignin in polymers faced challenges in achieving desired properties and processability.

Purpose of the Study:

• To synthesize biobased epoxy resins from hardwood lignin.
• To create epoxy thermoset polymers by blending these biobased resins with a conventional epoxy.
• To evaluate the mechanical properties and biobased content of the resulting polymers.

Main Methods:

• Hardwood lignin (from Eucalyptus) was depolymerized into oils via palladium-catalyzed hydrogenolysis.
• Lignin oils were reacted with epichlorohydrin to form biobased epoxy resins.
• These resins were blended with bisphenol A diglycidyl ether (BADGE) and cured with diethylenetriamine.

Main Results:

• High yields (up to 98 wt %) of lignin oils were obtained.
• Biobased epoxy resins were successfully synthesized from hardwood lignin hydrogenolysis oils.
• Up to 67% of BADGE could be replaced by lignin-derived epoxy resins, yielding polymers with superior or equivalent mechanical properties.
• Performance differences between hardwood and softwood lignin-based polymers were observed.

Conclusions:

• Hardwood lignin is a viable precursor for high-performance biobased epoxy thermoset polymers.
• Significant replacement of petroleum-based BADGE is achievable with lignin-derived epoxies.
• Further research into hardwood versus softwood lignin utilization can optimize biobased thermoset polymer development.