A novel multi-functional bio-based reactive diluent derived from cardanol for high bio-content UV-curable coatings application

A cardanol-based UV-curable reactive diluent (CACAA) was synthesized via two facile acrylation reactions and then copolymerized with acrylated epoxidized soybean oil (AESO) under UV irradiation to prepare cured films with high bio-based content. For comparison, petroleum-based reactive diluents, including pentaerythritol triacrylate (PETA) and bisphenol-A ethoxylated (2) diacrylate (BPAEODA), were also used to copolymerize with AESO under UV irradiation. The characterizations of 1H NMR and FT-IR were implemented to confirm the chemical structure of CACAA. The bio-based content and rheological behavior of the coating solutions with different diluents were compared. Besides, the gel content, volume shrinkage and solvent absorption of the UV-cured films were measured. Furthermore, the dynamic mechanical properties (via DMA), thermal stability (via TGA), mechanical properties (via tensile test) and coating properties (such as coating hardness, solvent resistance, and glossiness) of the UV-cured films were studied. Results revealed that the addition of CACAA could significantly improve the gel content, glass transition temperature, tensile strength and solvent resistance of the cured AESO films. Besides, CACAA exhibited better dilution effect and lower volume shrinkage than petroleum-based diluents (PETA and BPAEODA). Therefore, the cardanol-based UV-curable reactive diluent (CACAA) shows great potential to substitute petroleum-based diluents to prepare low-viscosity and low-shrinkage UV-curable coatings with high bio-based content. Also, the novel method proposed in this study provides a guideline to the preparation of highly bio-based coatings, and it will facilitate the development of bio-based polymers.