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 1 H 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.