Poly(furfuryl alcohol) as a Surface Modifier for Cellulose Nanocrystals Reinforced HDPE Nanocomposites

To overcome the thermodynamic incompatibility between hydrophilic cellulose nanocrystals (CNCs) and nonpolar polyolefins without relying on traditional fossil-based or solvent-heavy covalent compatibilizers, this study introduces a fully biobased, noncovalent strategy. We propose the in situ aqueous polymerization of poly(furfuryl alcohol) (PFA) to create a hydrophobic core-shell morphology around CNCs, enabling efficient melt-blending with high-density polyethylene (HDPE). Morphological and spectroscopic analyses confirmed the successful physical encapsulation, preserving the nanocrystals' structural integrity. Consequently, the PFA-modified nanocomposites exhibited robust interfacial adhesion, achieving a 42% increase in Young's modulus (1856 MPa) alongside enhanced specific strength. Furthermore, the PFA shell acted as an effective thermal barrier, increasing the CNC degradation onset from 250 to 360 °C, and enhanced matrix crystallinity by 9.7%. This facile, green modification distinguishes itself by bridging the polarity gap without toxic solvents, offering a highly scalable route for sustainable structural biocomposites.