Incorporation of Lignin in Bio-Based Resins for Potential Application in Fiber-Polymer Composites

Bio-based resins, obtained from renewable raw materials, are a more sustainable alternative to oil-based resins for fiber-reinforced polymer (FRP) composites. The incorporation of lignin in those resins has the potential to enhance their performance. This paper presents results of an experimental study about the effects of Lignoboost lignin incorporation on a partially bio-based vinyl ester (VE) resin. Two resins were prepared-without (reference) and with lignin addition (4% by weight) to its main chain-and their chemical, thermophysical, and mechanical properties were compared using Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), and tensile and shear tests. Results suggest that the addition of lignin to the base resin resulted in a copolymer of increased heterogeneity and higher molecular weight, incorporating stiff and complex aromatic structures in the polymer chain. While requiring high-temperature curing, the VE-lignin copolymer presented improvements of 27% in tensile strength, 4% in shear strength, and increased glass transition temperature by about 8 & DEG;C, thus confirming the potential of this natural biopolymer for FRP composite applications.