Effect of double bond position and density on properties of UV-induced bio-based polyurethane adhesion-reducing adhesives

In this paper, hydroxyl terminated copolyesters with different double bond position and density were prepared from bio-based dibasic acids. Bio-based unsaturated polyesters with -C=CH ₂ in side (MPIA), -CH=CH- in main chain (MPFA), and with -C=CH ₂ in side and -CH=CH- in main chain together (BDIA) were synthesized by using itaconic acid, fumaric acid, cis -2-butene-1,4-diol, and 2-methyl-1,3-propanediol as raw materials. The number molecular weight of MPIA, MPFA and BDIA was controlled almost the same. UV-induced bio-based polyurethane adhesion-reducing adhesives (BPURA) was prepared by bio-based unsaturated polyester, isophorone diisocyanate (IPDI), chain extender and photoinitiator. BPURA produced by MPIA, MPFA and BDIA were named BPURA-1, BPURA-2 and BPURA-3, respectively. The 180 ⁰ peel strength before and after UV irradiation of BPURA-1 was 22.07 and 0.17 N/25 mm, while that of BPURA-2 was 8.56 and 0.34 N/25 mm, respectively. It could be found that the contribution of 180 ⁰ peel strength of -C=CH ₂ in side (BPURA-1) was greater than that of -CH=CH- in the main chain (BPURA-2). SEM and 3D laser measurement microscope showed that BPURA-3 had the highest roughness after UV irradiation, which is conducive to the viscosity reduction effect of the adhesive. The 180 ⁰ peel strength before and after UV irradiation of BPURA-3 was 21.22 and 0.11 N/25 mm, respectively, which meets the bond strength standard of temporary bonding adhesive during wafer processing.