Thermally-Degradable Thermoset Adhesive Based on a Cellulose Nanocrystals/Epoxy Nanocomposite

For high-value components, reusability is often an important design consideration. For adhesively joined parts, the disassembly mechanism can be a key factor, and in some cases the thermal degradability of adhesives determines the reusability and recyclability of the components. After use, components that can be easily separated are generally more easily reused, but this requires controlled and well-understood adhesive degradation. Here, polymer nanocomposites based on epoxy resin and cellulose nanocrystals (CNCs) were fabricated, and their properties were examined as degradable adhesives. The distribution of CNCs within the epoxy resin was investigated by electron microscopy and mass spectroscopy. By incorporating CNCs into epoxy matrices, the shear strength of nanocomposites was improved by 31% and the effective thermal degradation temperature was reduced by 40 °C. Additionally, chemical analysis by X-ray photoelectron spectroscopy showed that sulfonate groups on the surface of CNCs play a critical role over improving the mechanical properties, while thermally induced breakage of these bonds mediates the thermal degradation of the nanocomposite.