Biobased Unsaturated Polyester Thermosets from Castor Oil and Isosorbide with Life Cycle Assessment

The development of low-carbon and environmentally friendly unsaturated polyester thermosets has attracted widespread attention. In this work, methacrylated castor oil (MCO) and methacrylated isosorbide (MI) were prepared using renewable castor oil and isosorbide by a simple and mild method. Subsequently, a variety of sustainable unsaturated polyester materials (MCO-MI) were prepared by curing MCO resin with the reactive diluent MI in different ratios via free radical polymerization. The chemical structure, viscosity, biobased carbon content, and LD50 of MCO and MI were evaluated, and the mechanical properties, thermo-mechanical properties, solvent resistance, and life cycle assessment (LCA) of the cured MCO-MI thermosets were investigated. The results showed that MCO and MI exhibited low viscosity (746 and 4 mPa s), chemical toxicity, and high biobased carbon content (85.9 and 76.9%). When the mass ratio of MCO to MI was 40:60, the resulting MCO-MI thermosets had the optimum thermo-mechanical property with a Tg of 170.2 °C and a tensile strength of 35.6 MPa. In addition, the LCA results demonstrated that the MCO-MI thermosets had striking environmental benefits over traditional petroleum-based unsaturated polyester materials containing styrene. This work provides insight into the preparation of environmentally friendly and high-performance unsaturated polyester materials employing biobased building blocks.