Fully bio-based thermoset composites from UV curable prepregs: Vegetable oil acrylate impregnated hemp nanopaper

Modern thermoset composite matrices are primarily prepared from petroleum-based plastics, while reinforcements commonly consist of non-renewable and energy-demanding glass and carbon fibers. Herein, a non-chemically treated hemp fiber-reinforced composite was prepared from bio-based components: hemp nanopaper (NP) and acrylated epoxidized soybean oil (AESO) or acrylated rapeseed oil (ARO). A commercial-grade AESO was selected as a reference and compared to ARO prepared in a one-step synthesis. The impregnation process was examined in detail by studying the impact of surface wetting, temperature, and vacuum on the composite structure. ARO has excellent fiber surface wettability, showing initial contact angles between 46.5° and 48.2° on hemp NP. A more than 10-fold difference in viscosity between AESO and ARO was observed. ARO composite with 50 wt% hemp loading achieved a Young's modulus of 1.3 GPa, a tensile strength of 26 MPa, and a storage modulus of 4.4 GPa (at 20°C). The results are supplemented by scanning electron microscope analysis of composite morphology via liquid nitrogen fracture and tensile failure analysis, that is, fractography. Dielectric spectroscopy analysis shows that composites have the potential to replace epoxy/paper composite insulators.