# Triketone-Modified Lignin and the Corresponding Biomass-Based Diketoenamine Resins: Synthesis and Properties

## TL;DR

Researchers created a new type of eco-friendly resin using modified lignin, which has good thermal properties but needs optimization for mechanical strength and recyclability.

## Contribution

A new lignin-based diketoenamine resin is synthesized with improved thermal properties and recyclability.

## Key findings

- The resin has a glass transition temperature of about 165 °C, higher than other similar resins.
- Adding 3 wt% OL-TK improves mechanical properties and reduces creep without affecting thermal recycling.
- High OL-TK content (7 wt%) causes lignin aggregation and reduces recyclability.

## Abstract

This work reports the preparation of environmentally
benign polymeric
materials by employing biomass-based raw materials in the synthesis
of recyclable thermosetting resins. With water-soluble lignin (possessing
−COOH groups) as a feedstock, lignin-triketone (OL-TK) is prepared
and cross-linked with tris­(2-aminoethyl)­amine (TREN) to result in
the corresponding lignin-based diketoenamine resins. The resin shows
a glass transition temperature (T

g
) of about 165 °C, which is higher than the values reported
for other diketoenamine resins and other lignin-based vitrimers due
to the relatively rigid structure of lignin and diketoenamine groups.
Nevertheless, the lignin-based diketoenamine resin shows high brittleness,
leading to failure in the mechanical tests. Further studies employ
OL-TK as a reactive modifier for a furanic dicarboxylic acid (FDCA)-based
diketoenamine resin. The lignin-containing diketoenamine resins exhibit
some features of vitrimers, including satisfactory stress relaxation
at 180 to 220 °C, thermal recycling ability, and chemical degradation/recycling
characteristics. The addition of 3 wt % OL-TK brings positive effects
on enhancing the mechanical properties and suppressing the creep at
high temperatures of the pristine resin and does not alter its thermal
properties and thermal recycling and reprocessing features. A high
OL-TK fraction of 7 wt %, although further increasing the mechanical
property and stress relaxation of the vitrimers, would result in lignin
aggregation in the thermally recycled sample. High OL-TK content is
negative for the recycling performance of the vitrimers.