Design, preparation and properties of novel flame retardant thermosetting vinyl ester copolymers based on castor oil and industrial dipentene

A novel bio-based flame-retardant thermosetting vinyl ester resin monomer was synthesized from castor oil. The chemical structures of the monomer was characterized by FTIR and 1H-NMR. In order to improve its rigidity and expand its application in the field of bio-based materials, it was mixed with certain proportions of another reactive bio-based VER monomer, which had rigid and strong polar groups, and then a series of copolymers were prepared with thermal curing method. Then their tensile property, hardness, morphology of fractured surface, flame retardant property, DMA and thermostability were all investigated. The results indicated that the copolymers had relatively high tensile strength of 11.2 MPa, and the limiting oxygen index is above 23% in all prepared copolymers. DMA demonstrates that the glass transition temperature of the cured resins is up to 56.1°C. Thermogravimetric analysis shows that the copolymers have excellent thermal stability.