Tyrosine-Modified surface coated Lignin as a Bio-Based Filler in HDPE matrix

Lignin, the second most abundant natural polymer following cellulose, is receiving considerable interest as a renewable resource capable of diminishing dependence on fossil fuels and improving the environmental sustainability of polymer composites [1]. While unmodified lignin offers inherent benefits like thermal stability, flame retardancy and antioxidant properties, its poor compatibility with hydrophobic matrices often limits its incorporation to only a small amount. As a result, a variety of chemical modification strategies are utilized to produce value-added lignin derivatives, hence enhancing its applicability in green polymeric materials [2].

In this work, lignin modified with tyrosine (Lig-Tyr) was incorporated into the HDPE matrix via melt mixing at 190 °C, in five different loadings 1 wt.%, 5 wt.%, 10 wt.%, 20 wt.%, and 30 wt.%. The final composites were characterized in terms of their structure through Fourier-transform infrared spectroscopy (FTIR). Their thermal behavior was evaluated via Differential Scanning Calorimetry and revealed no significant alteration of the HDPE properties after lignin incorporation, while mechanical behavior was deteriorated especially in filler loadings higher than 10 wt.%. Finally, the investigation of antioxidant properties through the DPPH method suggested enhanced antioxidant capacity compared to the neat polymer.

Acknowledgements

This project has received funding from the European Union's Horizon Europe Framework Programme under Grant Agreement No 101058449. Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or HADEA. Neither the European Union nor the granting authority can be held responsible for them.