Enhancing Water Resistance in Cationic Cellulose Nanofibril Adhesive with Natural Rubber Latex

Adhesives prepared with renewable materials through environmentally friendly processing offer an appealing alternative to their petroleum-based counterparts. Herein, we evaluated the adhesive properties of cationic cellulose nanofibrils (CCNFs) under dry and wet conditions and after mixing with natural rubber latex (NRL). Uniaxial tensile tests of negatively charged substrates (paper, aluminum (Al), and polypropylene (PP)) bonded with CCNF show a maximum lap shear strength that approached the failure point of the substrates, indicating the formation of a robust adhesive joint. The wet adhesion of CCNFs was improved (53% for PP and 154% for Al) by simple aqueous mixing with NRL suspension. This straightforward methodology promotes controlled CCNF and NRL electrostatic assembly that reduces the swelling of nanofibrils by water and improves adhesive cohesion. Cryogenic transmission electron microscopy images of CCNF/NRL complexes reveal that NRL particles are coated by a fibrillar CCNF network, providing morphological evidence that cationic nanofibrils contribute to interfacial adhesion to the solid substrates, while NRL enhances water resistance. This study presents a simple method to control noncovalent interactions and prepare nanocellulose-based adhesives with good mechanical properties and improved water resistance that are suitable for developing adhesives for different fields.