Development of high‐performance partially biobased thermoset polyester using renewable building blocks from isosorbide, 1,3‐propanediol, and fumaric acid

Research on biobased thermoset resins has been overlooked when compared with the rapid progress on biobased thermoplastics. The objective of this work was to develop unsaturated polyester prepolymers based on building blocks derived from renewable raw materials, namely, biobased isosorbide, 1,3‐propanediol, and fumaric acid, with petroleum‐derived phthalic anhydride. The prepolymers developed herein behaved as low‐molecular weight macromolecules (oligoesters), with Mn varying between 1.2 and 1.5 kDa, but achieved a high bio‐content of up to 87.1 wt%. The prepolymers were incorporated into reactive diluents comprising a blend of 2‐hydroxyethyl methacrylate and styrene, formulated to be eco‐friendlier and less toxic than typical styrene‐only incorporation approach, thus resulting in resins with viscosities between 750 and 950 cP. These resins are suitable for use in various fiber‐reinforced polymer production techniques, such as manual lamination, vacuum infusion, and pultrusion, having the benefit of presenting over 50 wt% of bio‐content in some formulations. Moreover, the crosslinked polyester resins (thermosets) exhibit comparable mechanical and thermomechanical behavior to their petrochemical‐based counterparts, with modulus of elasticity and tensile strength of up to 3.9 GPa and 62.1 MPa, respectively, and glass transition temperatures of up to 106°C, making them greener alternatives for high‐performance structural applications. This article presents the development of biobased unsaturated polyesters based on building blocks synthesized with monomers produced from renewable raw materials, namely, isosorbide, 1,3‐propanediol, and fumaric acid, with petroleum‐derived phthalic anhydride. A blend between styrene and a less toxic acrylate‐type monomer (2‐hydroethyl methacrylate) is used as a reactive diluent, resulting in biobased crosslinked resins suitable for various high‐performance applications.