Tough Bio-Based Thermosets with Dual Curing Capability Via Epoxy and Allylic Functionality

Acrylic monomer from high oleic soybean oil (HO-SBM) was combined with aromatic counterpart, 2-glycidoxy-5-vinylanisole (GVA), in chain copolymerization to design tough biobased thermosets with a dual-curing capability. Under specified conditions, a polymer network can be formed by either selective cross-linking of GVA’s epoxy (in the presence of amines) or HO-SBM allylic (by autooxidation) groups or dual-curing where epoxy-amine and autoxidation mechanisms coexist. Glass transition temperature of the synthesized copolymers increases with the GVA content, although the values fall in a rather narrow range (-10 °C to 7 °C). The latter fact allows to investigate the impact of the cross-linking mechanism on thermoset properties and coatings performance in more detail.Thermosets obtained via epoxy-amine and dual-curing have a significantly denser network when compared to autooxidation. An increase of GVA fraction in the chain (from 37 to 44 wt.%) noticeably increases Young’s modulus of thermosets (up to 235 MPa), while crosslinked by autooxidation polymer networks still possess elastomeric behavior. A substantial toughness increase at the rubbery plateau was observed for epoxy-amine and dual-curing thermosets based on 44 wt.% of GVA. After curing, both materials remain flexible and can be considered tough plastic. Increasing cross-link density led to improved chemical (solvent) resistance and hardness of thermoset coatings.