Toward Sustainable Adhesives with Biodegradability, Scalability, and Removability: Poly(butylene succinate)-Based Hot-Melt Adhesives

Abstract

Previous studies aiming to achieve sustainability in adhesive materials, primarily focused on the integration of bioderived or biodegradable components. However, existing sustainable adhesives often prioritize permanent adhesion over removability, which limits their recyclability. Herein, we introduce an innovative approach for producing scalable, biodegradable, and removable hot-melt adhesives, offering sustainability. Polybutylene succinate (PBS) was selected as the base polymer because of its excellent melt processability, biodegradability, and commercial availability. To impart adhesiveness, three biomass-derived tackifiers were incorporated; basic rosin, disproportionated rosin, and rosin ester. The use of a twin-screw extruder enabled the efficient mixing of the base polymer and tackifiers for large-scale production at the kilogram scale. Our investigation revealed that basic rosin exhibited optimal compatibility and wettability, which were attributed to its high acid value. The high acid value promoted rapid crystallization and minimized crystal defects. A correlation between the crystallization behavior and adhesion strength was also established, identifying the optimal composition. The optimal composition yields a satisfactory adhesion strength (2.5 N/25 mm) that makes it suitable for removable or repositionable adhesives. Additionally, our optimized adhesive exhibited sufficient biodegradability and was completely decomposed by lipase within 21 d, which has not been observed in previous sustainable hot-melt adhesive studies. This study provides a practical pathway for enhancing adhesive sustainability with the potential for further advancements in tailoring the adhesion strength for diverse applications in future research.