Hempseed Oil-Based Covalent Adaptable Epoxy-Amine Network and Its Potential Use for Room-Temperature Curable Coatings

Conventional thermoset coatings are prepared from petrochemical feedstocks, which are nonrenewable, and the resulting coatings are not repairable. To extent the service life and meet the sustainable demands, it is desirable to develop repairable coatings prepared from renewable feedstocks. Dynamic covalent chemistry can impart thermosetting polymers the repairability. However, such alternative polymers that are also room-temperature curable are rare. In this work, a room-temperature curable epoxy vitrimer is introduced by curing a mixture of hempseed oil-based glycidyl ester-type epoxy (HOEP) and a bisphenol A-based digycidyl ether-type epoxy with diethylenetriamine (DETA). The resulting cross-linked network possesses abundant ester bonds and hydroxyl groups, which can undergo dynamic transesterification reactions at elevated temperatures and provide typical vitrimer behaviors such as stress relaxation and reparability to the cured resin. Coatings of this resin system on tin plates prepared at room temperature exhibit satisfactory glass transition temperature (>40 degrees C), scratch hardness (5H), gouge hardness (6H), adhesive strength (5B), and solvent resistance. The renewable HOEP accounts for up to 67.5 wt % in the composition. This work has demonstrated a simple method for the preparation of a room-temperature curable epoxy vitrimer using a glycidyl ester epoxy as a co-monomer and an aliphatic amine as the hardener, which is readily pluggable into current epoxy commercial products.