Tung Oil-Based Unsaturated Co-ester Macromonomer for Thermosetting Polymers: Synergetic Synthesis and Copolymerization with Styrene

A novel unsaturated co-ester (co-UE) macro monomer containing both maleates and acrylates was synthesized from tung oil (TO) and its chemical structure was characterized by FT-IR, H-1 NMR, C-13 NMR, and gel permeation chromatography (GPC). The monomer was synthesized via a new synergetic modification of TO, by introducing maleic groups first and acrylic groups subsequently onto TO molecules. The influence of experimental factors on thermomechanical properties of the . cured bioresins was evaluated to better understand structure property relationships of the biomaterials and optimize experimental conditions. The obtained TO-based co-UE monomer possessed a highly polymerizable C=C functionality, consequently resulting in rigid bioplastics with high cross-link densities (v(e)) and excellent mechanical properties. For instance, the bioplastic prepared under the optimal synthesis conditions demonstrated a v(e) of 4.03 X 10(3) mol/m(3), storage modulus at 25 degrees C of 2.40 GPa, and glass transition temperature (T-g) of 127 degrees C, as well as tensile strength and modulus at 36.3 MPa and 1.70 GPa, respectively. A new theory for determining optimal comonomer concentration was further developed according to the copolymerization equation. The proposed theory accurately predicted the best styrene dosage for the co-UE monomer. At last, the hydroxyethyl acrylate (HEA)-modified TO-based resin was compared with the unmodified one in thermomechanical properties, thermal stability, microstructural morphologies, and curing behaviors. The new co-UE bioresin showed higher C=C functionality and cross-link density, superior properties including T-g and thermal stability, and similar curing behaviors. The developed eco-friendly rigid biomaterials provide potential application in structural plastics such as sheet molding compounds.