Toward Sustainable\nAdhesives with Biodegradability,\nScalability, and Removability: Poly(butylene succinate)-Based Hot-Melt\nAdhesives

Previous studies aiming to achieve sustainability in\nadhesive materials,\nprimarily focused on the integration of bioderived or biodegradable\ncomponents. However, existing sustainable adhesives often prioritize\npermanent adhesion over removability, which limits their recyclability.\nHerein, we introduce an innovative approach for producing scalable,\nbiodegradable, and removable hot-melt adhesives, offering sustainability.\nPolybutylene succinate (PBS) was selected as the base polymer because\nof its excellent melt processability, biodegradability, and commercial\navailability. To impart adhesiveness, three biomass-derived tackifiers\nwere incorporated; basic rosin, disproportionated rosin, and rosin\nester. The use of a twin-screw extruder enabled the efficient mixing\nof the base polymer and tackifiers for large-scale production at the\nkilogram scale. Our investigation revealed that basic rosin exhibited\noptimal compatibility and wettability, which were attributed to its\nhigh acid value. The high acid value promoted rapid crystallization\nand minimized crystal defects. A correlation between the crystallization\nbehavior and adhesion strength was also established, identifying the\noptimal composition. The optimal composition yields a satisfactory\nadhesion strength (2.5 N/25 mm) that makes it suitable for removable\nor repositionable adhesives. Additionally, our optimized adhesive\nexhibited sufficient biodegradability and was completely decomposed\nby lipase within 21 d, which has not been observed in previous sustainable\nhot-melt adhesive studies. This study provides a practical pathway\nfor enhancing adhesive sustainability with the potential for further\nadvancements in tailoring the adhesion strength for diverse applications\nin future research.