Investigation of Bio-based Acrylate Reactive Diluents for UV-curable Electronic Packaging Polyurethane Adhesives

Abstract

Traditional acrylate reactive diluents, which are derived from fossil resources, are known to exhibit significant irritation and allergenic potential, leading to their prohibition in high-end electronics, particularly in wearable devices. To address these limitations, four bio-based acrylate reactive diluents (BRDs) were synthesized via the reaction of alcohols derived from renewable sources, piperitol, vanillin, eugenol, and isosorbide, with methacrylic anhydride. The viscosity of the synthesized BRDs and the T_g of their corresponding polymers were systematically evaluated and compared with those of the petroleum-based diluent isobornyl acrylate (IBOA). The BRDs were then blended with acrylate-terminated polyurethane (APU) to formulate a series of UV-curable polyurethane adhesives (APU-BRDs). The results suggest that BRDs effectively reduce the viscosity of APU. By selecting and combining BRDs, the bonding strength of APU-BRDs to polar substrates such as PC and glass can reach 20 MPa. Even for non-polar substrates like PE, the strength is close to 5 MPa. The values obtained in this study exceed those of adhesives prepared using the conventional petroleum-based diluent IBOA. Furthermore, the study explored the potential application of APU-BRDs in smart wearable devices, confirming their suitability for next-generation wearable technology.