Development and Characterization of a Sustainable Lignin-based Composite Material

Sammanfattning: Lignin is the most abundant aromatic polymer of natural origin on earth. Currently, it is treated as a waste product of the paper production industry and is burnt as fuel to generate energy. Due to its renewable nature, it represents instead an optimum candidate to substitute non-renewable fossil-based feedstock for the production of plastic products. The present Thesis project deals with the development and characterization of a composite material, made of a lignin-based polymer matrix reinforced with glass fibers. The polymer blend used as matrix, composed of 50% by weight of lignin and 50% of DGEBA, once cured, was found to have a high gel content, corresponding to more than 97%. Moreover, it possesses a significant thermal stability: it starts to degrade at around 250 °C, it loses less than 5% of its weight up to 300 °C (of which 2% is water) and has its maximum degradation rate at 411 °C. Composites made of lignin-DGEBA matrix, reinforced with different contents of short glass fibers, from 10% to 60% of the matrix weight, were prepared. The developed composites showed a considerably decreasing porosity with increasing fiber content, up to the 50% glass fiber composite. In addition, from scanning electron microscopy images, a strong adhesion force between matrix and glass fibers was revealed.Furthermore, tensile tests showed that the produced composites have a good stiffness. In fact, the Young’s modulus varies from slightly more than 4 GPa of the 30% glass fiber composite to almost 5 GPa of the 50% composite, decreasing then in the 60% one.