Fuente: Journal of applied polymer Lugar: RESEARCH ARTICLE The trifunctional rosin-based vinyl ester (MEH) resins are successfully synthesized via Diels-Alder addition reaction, followed by epoxidation reaction and then epoxy ring-opening reaction. And the MEH-based UV cured coating films can attain the satisfactory mechanical toughness and adhesion property, and effective thermal and chemical stabilities, which have promising potential applications in the biobased UV curable coating fileds.

ABSTRACT
With the growing emphasis on sustainable development and low-carbon economy, bio-based UV curable resins with outstanding mechanical toughness and adhesion performance are increasingly significant alternatives to their petroleum-based counterparts in coatings fields. In this work, trifunctional rosin-based vinyl ester (MEH) resins are successfully synthesized via Diels-Alder addition reaction of levopimaric acid and maleic anhydride, followed by epoxidation reaction with epichlorohydrin and then epoxy ring-opening reaction with hydroxyethyl methacrylated maleate (HEMMA). By integrating the rigidity of rosin skeleton with the flexibility and UV reactivity of HEMMA segments, the synthesized MEH resin served as an effective matrix resin for UV curable coatings. Particularly, the optimized rosin-based UV cured coating film displays favorable comprehensive performances with gel content exceeding 95%, glass transition temperature of 102.13°C, tensile strength of 71.23 MPa, elongation at break of 7.75%, and lap shear strength up to 7.86 MPa. Moreover, the prepared rosin-based coating films have outstanding resistance to solvents and acids. Overall, this study provides an effective strategy for constructing rosin-based UV curable coatings with satisfactory mechanical toughness and adhesion property, and effective thermal and chemical stabilities, which display the great utilization potential in high mechanical toughness and adhesion requirements of UV curable coatings.