Fully bio-based pressure sensitive adhesives using amylopectin

Abstract

A facile and innovative strategy to design bio-based, processible, reusable, and self-healing pressure sensitive adhesive (PSA) is developed. In this work, 100% of PSA composition is replaced with fully bio-based, bio-degradable, renewable, and even edible feedstock via only a simple and eco-friendly process excluding any use of solvents or chemical reagents. The PSA formulation is based on a colloidal mixture of amylopectin nanoparticles (AMPs), cellulose nanofibrils (CNFs), and either sorbitol (SBT) or mannitol (MNT), which play crucial roles as a firm base, reinforcing structural support, and a plasticizer/binder, respectively, combined with glycerol in the presence (1$^{st}$ approach) and absence (2$^{nd}$ approach) of water. Both approaches can yield excellent rheological and adhesion properties, which are comparable to conventional petrochemical-based products in terms of tack, peel, and shear strength, by leveraging physical crosslinking through hydrogen bonding among the constituents, especially between AMPs and SBT/MNT, and by balancing bulk viscoelastic properties. While the water-based PSA is vulnerable to high humidity, the glycerol-based PSA becomes so humidity-resistant that the relative humidity over 90% can’t deteriorate its peel and shear strength. The optimal glycerol-based formulation also showcases a high self-healing ability. While there are areas for further optimization, this work provides a foundational step towards the most sustainable adhesive industry.