Incorporation of Cellulose Nanocrystals and Reactive Surfactants for Improved Pressure Sensitive Adhesive Performance

Pressure sensitive adhesives (PSAs), which achieve instantaneous adhesion with the application of light pressure, are used in a large range of commodity applications. Aqueous emulsion polymerizations have become a commonly employed synthetic procedure for PSA development, as it is a more sustainable practice that avoids the use of organic solvents and is well-suited to the introduction of additives that can more precisely tune PSA performance. Cellulose nanocrystals (CNCs) have recently become an additive of interest due to their high abundance in nature, biodegradability, and high modulus. However, a persistent challenge with PSAs formed via in-situ emulsion polymerization is surfactant segregation, particularly during adhesive application and drying.

In this work, PSAs enriched with cellulose nanocrystals (CNCs) were synthesized via in-situ emulsion polymerization. In addition to the inclusion of CNCs in the PSAs, the formulations were stabilized with a reactive surfactant (Hitenol AR-1025, AR) to address surfactant segregation and further enhance adhesive performance. The incorporation of both CNCs reactive surfactant lead to a drastic improvement of peel strength, shear strength, and loop tack with peak properties observed at a CNC concentration of 0.75 parts per hundred monomer (phm). A comparative investigation of PSAs utilizing non-reactive (sodium dodecyl sulfate) surfactant revealed that the enhanced performance can be attributed to the synergistic combination of CNCs and reactive surfactant, as only modest improvements can be attributed to surfactant type. In contrast to previous studies that report a trade-off in adhesive properties, this work presents a well-rounded PSA with exceptional peel strength, shear strength, and loop tack.