Lignin from second-generation biorefinery for pressure-sensitive adhesive tapes

In this work, the potential of lignin as a filler additive and anti-aging agent in a pressure-sensitive adhesive (PSA) based on natural rubber (NR) was investigated. Herein, different approaches to incorporate lignin into NR matrix by adaptation of a two-step compounding process were evaluated. At first, a twin-screw extruder (TSE) was utilized to prepare pre-formulations followed by the secondary finalization of adhesive mass inside a planetary roll extruder (PRE). For the industrial production of PSAs, the adhesive mass is required to have well-distributed additive materials and adequate adhesion, cohesion, and longevity. The impact of the added lignin was evaluated concerning optical appearance, compatibility between lignin and rubber/resin, adhesion performance, shear strength, thermal stability, antioxidant capability, dynamic-mechanical behavior, aging behavior at elevated temperature and under UV exposure, and filler morphology. It was found that the PSAs including aquasolv (AS) lignin after the spray-drying post-treatment exhibited excellent thermal, mechanical, and antioxidative properties. Thus, it was shown that the sustainably producible lignin can be utilized both as filler and antioxidant in natural rubber-based pressure-sensitive adhesive masses with comparable performance properties as commercially available products.