Synergistic Effects of Low-Loading Cellulose Nanocrystals on the Mechanical, Morphological, Thermal, and Structural Properties of Epoxy Resins

Epoxy resins have attracted considerable attention as versatile adhesives due to their structural stability, chemical inertness, and excellent resistance to oxidation. Their performance can be further enhanced through the incorporation of various additives designed for specific applications. In the present study, cellulose nanocrystals (CNCs), recognized for their high mechanical properties, were employed as a reinforcing agent. CNCs were incorporated into the epoxy resin at loading ratios of 0.0625%, 0.125%, 0.25%, and 0.5% to produce the nanocomposites. According to the obtained results, the lowest reductions observed in flexural and tensile strengths were 13% and 16%, respectively, while the highest increases in flexural and tensile modulus were 18% and 50%, respectively. Morphological analyses revealed that CNCs were not homogeneously distributed within the matrix, particularly at higher concentrations, where agglomeration likely contributed to the observed declines in mechanical performance. Thermogravimetric analysis (TGA) indicated a slight improvement in thermal stability at lower CNC loadings; however, thermal stability diminished at higher CNC concentrations. X-ray diffraction (XRD) analysis demonstrated that the neat epoxy exhibited the highest crystallinity index (CI, 62%), which progressively decreased with increasing CNC content, resulting in a more amorphous nanocomposite structure.